diff --git a/index.org b/index.org
index 3047628..1795a3c 100644
--- a/index.org
+++ b/index.org
@@ -74,7 +74,7 @@ The station is identified again.
 
 * Measurements of perturbations
 - [[file:slip-ring-spindle-vibrations/index.org][Measurement of the vibrations induced by the rotation of the slip-ring and spindle]]
-- Measurement of the electrical noise induced by the slip-ring
+- [[file:slip-ring-electrical-noise/index.org][Measurement of the electrical noise induced by the slip-ring]]
 
 ** Noise coming from the control loop of each stage
 [[file:2018-10-15%20-%20Marc/index.org][Link to the analysis]]
diff --git a/slip-ring-electrical-noise/figs/slipring_asd.png b/slip-ring-electrical-noise/figs/slipring_asd.png
index 7a00984..ecc308e 100644
Binary files a/slip-ring-electrical-noise/figs/slipring_asd.png and b/slip-ring-electrical-noise/figs/slipring_asd.png differ
diff --git a/slip-ring-electrical-noise/figs/slipring_time.png b/slip-ring-electrical-noise/figs/slipring_time.png
index 1412441..12db41a 100644
Binary files a/slip-ring-electrical-noise/figs/slipring_time.png and b/slip-ring-electrical-noise/figs/slipring_time.png differ
diff --git a/slip-ring-electrical-noise/index.html b/slip-ring-electrical-noise/index.html
index 633f118..1184a99 100644
--- a/slip-ring-electrical-noise/index.html
+++ b/slip-ring-electrical-noise/index.html
@@ -3,12 +3,12 @@
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
 <head>
-<!-- 2019-05-10 ven. 10:06 -->
+<!-- 2019-05-13 lun. 15:05 -->
 <meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
 <meta name="viewport" content="width=device-width, initial-scale=1" />
 <title>Measurements On the Slip-Ring</title>
 <meta name="generator" content="Org mode" />
-<meta name="author" content="Thomas Dehaeze" />
+<meta name="author" content="Dehaeze Thomas" />
 <style type="text/css">
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   .title  { text-align: center;
@@ -270,104 +270,138 @@ for the JavaScript code in this tag.
         src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js?config=TeX-AMS_HTML"></script>
 </head>
 <body>
-<div id="content">
+<div id="org-div-home-and-up">
+ <a accesskey="h" href="../index.html"> UP </a>
+ |
+ <a accesskey="H" href="../index.html"> HOME </a>
+</div><div id="content">
 <h1 class="title">Measurements On the Slip-Ring</h1>
 <div id="table-of-contents">
 <h2>Table of Contents</h2>
 <div id="text-table-of-contents">
 <ul>
-<li><a href="#org2781a7a">1. Effect of the Slip-Ring on the signal</a>
+<li><a href="#orgceb5a28">1. Effect of the Slip-Ring on the signal when turned ON - Geophone measurement</a>
 <ul>
-<li><a href="#org3dea630">1.1. Experimental Setup</a></li>
-<li><a href="#orgf0d1f5d">1.2. Load data</a></li>
-<li><a href="#org2b5c36e">1.3. Analysis - Time Domain</a></li>
-<li><a href="#org22f0fdc">1.4. Analysis - Frequency Domain</a></li>
-<li><a href="#org9abd380">1.5. Conclusion</a></li>
+<li><a href="#org636027c">1.1. Experimental Setup</a></li>
+<li><a href="#orgfa19de7">1.2. Load data</a></li>
+<li><a href="#orgd6fcaf4">1.3. Analysis - Time Domain</a></li>
+<li><a href="#orga1aff53">1.4. Analysis - Frequency Domain</a></li>
+<li><a href="#org56fbbb7">1.5. Conclusion</a></li>
 </ul>
 </li>
-<li><a href="#org6002a8c">2. Effect of the rotation of the Slip-Ring</a>
+<li><a href="#orga7d54ca">2. Measure of the noise induced by the Slip-Ring using voltage amplifiers - Geophone</a>
 <ul>
-<li><a href="#orgedc9c11">2.1. Measurement Description</a></li>
-<li><a href="#org5e95fbe">2.2. Load data</a></li>
-<li><a href="#org7a8e8fc">2.3. Analysis</a></li>
-<li><a href="#org24db8f6">2.4. Conclusion</a></li>
+<li><a href="#org5a59fd1">2.1. First Measurement without LPF</a>
+<ul>
+<li><a href="#org9e2424e">2.1.1. Measurement Description</a></li>
+<li><a href="#org1dd1ac5">2.1.2. Load data</a></li>
+<li><a href="#orgf20d3eb">2.1.3. Time Domain</a></li>
+<li><a href="#orge85c7f5">2.1.4. Frequency Domain</a></li>
+<li><a href="#orgdf83e7e">2.1.5. Conclusion</a></li>
 </ul>
 </li>
-<li><a href="#org21fc4d2">3. Measure of the noise induced by the Slip-Ring</a>
+<li><a href="#org0687474">2.2. Measurement using an oscilloscope</a>
 <ul>
-<li><a href="#org901cf1f">3.1. Measurement Description</a></li>
-<li><a href="#org3aa7c6d">3.2. Load data</a></li>
-<li><a href="#org22f6115">3.3. Time Domain</a></li>
-<li><a href="#orgd6cbe96">3.4. Frequency Domain</a></li>
-<li><a href="#orgbb89292">3.5. Conclusion</a></li>
+<li><a href="#org8d0ea64">2.2.1. Measurement Setup</a></li>
+<li><a href="#orgf090bd6">2.2.2. Observations</a></li>
+<li><a href="#org8d48fa3">2.2.3. Conclusion</a></li>
 </ul>
 </li>
-<li><a href="#orgf77f778">4. Measure of the noise induced by the slip ring when using a geophone</a>
+<li><a href="#org09cd59c">2.3. New measurements with a LPF before the Voltage Amplifiers</a>
 <ul>
-<li><a href="#org57fc212">4.1. First Measurement without LPF</a>
-<ul>
-<li><a href="#org4e633db">4.1.1. Measurement Description</a></li>
-<li><a href="#orge652945">4.1.2. Load data</a></li>
-<li><a href="#orgfdc44bc">4.1.3. Time Domain</a></li>
-<li><a href="#org1747240">4.1.4. Frequency Domain</a></li>
-<li><a href="#org2082a3e">4.1.5. Conclusion</a></li>
+<li><a href="#org36fc63d">2.3.1. Setup description</a></li>
+<li><a href="#org7823df0">2.3.2. Load data</a></li>
+<li><a href="#orga0f3ca7">2.3.3. Time Domain</a></li>
+<li><a href="#org3a55406">2.3.4. Frequency Domain</a></li>
+<li><a href="#orgf462896">2.3.5. Conclusion</a></li>
 </ul>
 </li>
-<li><a href="#org0d10493">4.2. Measurement using an oscilloscope</a>
-<ul>
-<li><a href="#org84a4af9">4.2.1. Measurement Setup</a></li>
-<li><a href="#orgba2e6ff">4.2.2. Observations</a></li>
-<li><a href="#org729aaf2">4.2.3. Conclusion</a></li>
+<li><a href="#orgfc76b2a">2.4. <span class="todo TODO">TODO</span> New LPF at 1kHz</a></li>
 </ul>
 </li>
-<li><a href="#orge6ed6b4">4.3. New measurements with a LPF before the Voltage Amplifiers</a>
+<li><a href="#orgf6fc986">3. Effect of the rotation of the Slip-Ring - Noise</a>
 <ul>
-<li><a href="#org4501bcc">4.3.1. Setup description</a></li>
-<li><a href="#org7f64f45">4.3.2. Load data</a></li>
-<li><a href="#org168648f">4.3.3. Time Domain</a></li>
-<li><a href="#org18b3f68">4.3.4. Frequency Domain</a></li>
-<li><a href="#org5c54c76">4.3.5. Comparison of with and without LPF</a></li>
-<li><a href="#org44b238b">4.3.6. Conclusion</a></li>
+<li><a href="#orgf659e9b">3.1. Measurement Description</a></li>
+<li><a href="#orgee42249">3.2. Load data</a></li>
+<li><a href="#org5ba0b07">3.3. Analysis</a></li>
+<li><a href="#org164ce5f">3.4. Conclusion</a></li>
 </ul>
 </li>
+<li><a href="#org88023e5">4. Measure of the noise induced by the Slip-Ring using voltage amplifiers - Noise</a>
+<ul>
+<li><a href="#org89e519f">4.1. Measurement Description</a></li>
+<li><a href="#orgc5c1ef8">4.2. Load data</a></li>
+<li><a href="#org68d7016">4.3. Time Domain</a></li>
+<li><a href="#org147ce89">4.4. Frequency Domain</a></li>
+<li><a href="#org7392479">4.5. Conclusion</a></li>
 </ul>
 </li>
 </ul>
 </div>
 </div>
 
-<div id="outline-container-org2781a7a" class="outline-2">
-<h2 id="org2781a7a"><span class="section-number-2">1</span> Effect of the Slip-Ring on the signal</h2>
+<ul class="org-ul">
+<li>Section <a href="#orga807ed4">1</a>
+<ul class="org-ul">
+<li>geophone located at the sample location is measured with its signal going directly to the ADC and going through the slip-ring</li>
+<li>The voltage amplifiers where saturating due to high frequency noise</li>
+</ul></li>
+<li>Section <a href="#orgc302908">2</a></li>
+</ul>
+
+<div id="outline-container-orgceb5a28" class="outline-2">
+<h2 id="orgceb5a28"><span class="section-number-2">1</span> Effect of the Slip-Ring on the signal when turned ON - Geophone measurement</h2>
 <div class="outline-text-2" id="text-1">
 <p>
-<a id="org8c43795"></a>
+<a id="orga807ed4"></a>
 </p>
 
+<div class="note">
 <p>
-The data and matlab files are accessible <a href="data/meas_slip_ring_geophone.zip">here</a>.
+All the files (data and Matlab scripts) are accessible <a href="data/meas_slip_ring_geophone.zip">here</a>.
 </p>
+
+</div>
 </div>
 
-<div id="outline-container-org3dea630" class="outline-3">
-<h3 id="org3dea630"><span class="section-number-3">1.1</span> Experimental Setup</h3>
+<div id="outline-container-org636027c" class="outline-3">
+<h3 id="org636027c"><span class="section-number-3">1.1</span> Experimental Setup</h3>
 <div class="outline-text-3" id="text-1-1">
 <p>
+<b>Goal</b>:
+The goal is to determine if some noise is added to a signal passing through the slip-ring.
+</p>
+
+
+<p>
+<b>Setup</b>:
 Two measurements are made with the control systems of all the stages turned OFF.
 </p>
 
 <p>
-One geophone is located on the marble while the other is located at the sample location (figure <a href="#orgc4f61a9">1</a>).
+One geophone is located on the marble while the other is located at the sample location (figure <a href="#org4499744">1</a>).
 </p>
 
+<p>
+The two signals from the geophones are amplified with voltage amplifiers with the following settings:
+</p>
+<ul class="org-ul">
+<li>Gain: 60dB</li>
+<li>AC/DC switch: AC</li>
+<li>Low pass filter at the output set at 1kHz</li>
+</ul>
 
-<div id="orgc4f61a9" class="figure">
+
+<div id="org4499744" class="figure">
 <p><img src="./img/IMG_20190430_112615.jpg" alt="IMG_20190430_112615.jpg" width="500px" />
 </p>
 <p><span class="figure-number">Figure 1: </span>Experimental Setup</p>
 </div>
 
+
 <p>
-The two measurements are:
+<b>Measurements</b>:
+Two measurements are done:
 </p>
 <table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
 
@@ -385,13 +419,13 @@ The two measurements are:
 </thead>
 <tbody>
 <tr>
-<td class="org-left"><code>meas_018.mat</code></td>
-<td class="org-left">Signal from the top geophone does not goes through the Slip-ring</td>
+<td class="org-left"><code>mat/meas_018.mat</code></td>
+<td class="org-left">Signal goes through the Slip-ring (as shown on the figure above)</td>
 </tr>
 
 <tr>
-<td class="org-left"><code>meas_019.mat</code></td>
-<td class="org-left">Signal goes through the Slip-ring (as shown on the figure above)</td>
+<td class="org-left"><code>mat/meas_019.mat</code></td>
+<td class="org-left">Signal from the top geophone does not goes through the Slip-ring</td>
 </tr>
 </tbody>
 </table>
@@ -433,34 +467,33 @@ Each of the measurement <code>mat</code> file contains one <code>data</code> arr
 </div>
 </div>
 
-<div id="outline-container-orgf0d1f5d" class="outline-3">
-<h3 id="orgf0d1f5d"><span class="section-number-3">1.2</span> Load data</h3>
+<div id="outline-container-orgfa19de7" class="outline-3">
+<h3 id="orgfa19de7"><span class="section-number-3">1.2</span> Load data</h3>
 <div class="outline-text-3" id="text-1-2">
 <p>
 We load the data of the z axis of two geophones.
 </p>
 
 <div class="org-src-container">
-<pre class="src src-matlab">d8 = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_018.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; d8 = d8.data;
-d9 = load<span class="org-rainbow-delimiters-depth-1">(</span>'mat<span class="org-type">/</span>data_019.mat', <span class="org-string">'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; d9 = d9.data;
+<pre class="src src-matlab">meas_sr = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_018.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; meas_sr = meas_sr.data;
+meas_di = load<span class="org-rainbow-delimiters-depth-1">(</span>'mat<span class="org-type">/</span>data_019.mat', <span class="org-string">'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; meas_di = meas_di.data;
 </pre>
 </div>
 </div>
 </div>
 
-<div id="outline-container-org2b5c36e" class="outline-3">
-<h3 id="org2b5c36e"><span class="section-number-3">1.3</span> Analysis - Time Domain</h3>
+<div id="outline-container-orgd6fcaf4" class="outline-3">
+<h3 id="orgd6fcaf4"><span class="section-number-3">1.3</span> Analysis - Time Domain</h3>
 <div class="outline-text-3" id="text-1-3">
 <p>
-First, we compare the time domain signals for the two experiments (figure <a href="#org49ef389">2</a>).
+First, we compare the time domain signals for the two experiments (figure <a href="#org9d1e6aa">2</a>).
 </p>
 
-
 <div class="org-src-container">
 <pre class="src src-matlab"><span class="org-type">figure</span>;
 hold on;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>d9<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-2">)</span>, d9<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'Slip-Ring'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>d8<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-2">)</span>, d8<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'Wire'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>meas_di<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-2">)</span>, meas_di<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'Geophone - Direct'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>meas_sr<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-2">)</span>, meas_sr<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'Geophone - Slip-Ring'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 hold off;
 xlabel<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Time </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">s</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">)</span></span><span class="org-string">; ylabel</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">(</span></span><span class="org-string">'Voltage </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">V</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">0</span>, <span class="org-highlight-numbers-number">50</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
@@ -469,39 +502,40 @@ legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-stri
 </div>
 
 
-<div id="org49ef389" class="figure">
+<div id="org9d1e6aa" class="figure">
 <p><img src="figs/slipring_time.png" alt="slipring_time.png" />
 </p>
-<p><span class="figure-number">Figure 2: </span>Effect of the Slip-Ring on the measured signal - Time domain</p>
+<p><span class="figure-number">Figure 2: </span>Effect of the Slip-Ring on the measured signal of the geophone at the sample location - Time domain</p>
 </div>
 </div>
 </div>
 
-<div id="outline-container-org22f0fdc" class="outline-3">
-<h3 id="org22f0fdc"><span class="section-number-3">1.4</span> Analysis - Frequency Domain</h3>
+<div id="outline-container-orga1aff53" class="outline-3">
+<h3 id="orga1aff53"><span class="section-number-3">1.4</span> Analysis - Frequency Domain</h3>
 <div class="outline-text-3" id="text-1-4">
 <p>
-We then compute the Power Spectral Density of the two signals and we compare them (figure <a href="#orgcc2d186">3</a>).
+We then compute the Power Spectral Density of the two signals and we compare them (figure <a href="#org0287fa9">3</a>).
 </p>
+
 <div class="org-src-container">
-<pre class="src src-matlab">dt = d8<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">2</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-1">)</span> <span class="org-type">-</span> d8<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">1</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+<pre class="src src-matlab">dt = meas_di<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">2</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-1">)</span> <span class="org-type">-</span> meas_di<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">1</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 Fs = <span class="org-highlight-numbers-number">1</span><span class="org-type">/</span>dt;
 
-win = hanning<span class="org-rainbow-delimiters-depth-1">(</span>ceil<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-highlight-numbers-number">1</span><span class="org-type">*</span>Fs<span class="org-rainbow-delimiters-depth-2">)</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+win = hanning<span class="org-rainbow-delimiters-depth-1">(</span>ceil<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-highlight-numbers-number">5</span><span class="org-type">*</span>Fs<span class="org-rainbow-delimiters-depth-2">)</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 </pre>
 </div>
 
 <div class="org-src-container">
-<pre class="src src-matlab"><span class="org-rainbow-delimiters-depth-1">[</span>pxx8, f<span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>d8<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
-<span class="org-rainbow-delimiters-depth-1">[</span>pxx9, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>d9<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
+<pre class="src src-matlab"><span class="org-rainbow-delimiters-depth-1">[</span>px_di, f<span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>meas_di<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
+<span class="org-rainbow-delimiters-depth-1">[</span>px_sr, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>meas_sr<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
 </pre>
 </div>
 
 <div class="org-src-container">
 <pre class="src src-matlab"><span class="org-type">figure</span>;
 hold on;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxx9<span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'Slip-Ring'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxx8<span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'Wire'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>px_sr<span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'Slip-Ring'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>px_di<span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'Wire'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 hold off;
 <span class="org-type">set</span><span class="org-rainbow-delimiters-depth-1">(</span><span class="org-variable-name">gca</span>, <span class="org-string">'xscale', 'log'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 <span class="org-type">set</span><span class="org-rainbow-delimiters-depth-1">(</span><span class="org-variable-name">gca</span>, <span class="org-string">'yscale', 'log'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
@@ -512,32 +546,22 @@ legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-stri
 </div>
 
 
-<div id="orgcc2d186" class="figure">
+<div id="org0287fa9" class="figure">
 <p><img src="figs/slipring_asd.png" alt="slipring_asd.png" />
 </p>
-<p><span class="figure-number">Figure 3: </span>Effect of the Slip-Ring on the measured signal - Frequency domain</p>
+<p><span class="figure-number">Figure 3: </span>Effect of the Slip-Ring on the measured signal of the geophone at the sample location - Frequency domain</p>
 </div>
 </div>
 </div>
 
-<div id="outline-container-org9abd380" class="outline-3">
-<h3 id="org9abd380"><span class="section-number-3">1.5</span> Conclusion</h3>
+<div id="outline-container-org56fbbb7" class="outline-3">
+<h3 id="org56fbbb7"><span class="section-number-3">1.5</span> Conclusion</h3>
 <div class="outline-text-3" id="text-1-5">
 <div class="important">
 <ul class="org-ul">
-<li>Connecting the geophone through the Slip-Ring seems to induce a lot of noise.</li>
-</ul>
-
-</div>
-
-<div class="note">
-<p>
-<b>Remaining questions to answer</b>:
-</p>
-<ul class="org-ul">
-<li>Why is there a sharp peak at 300Hz?</li>
-<li>Why the use of the Slip-Ring does induce a noise?</li>
-<li>Can the capacitive/inductive properties of the wires in the Slip-ring does not play well with the geophone? (resonant RLC circuit)</li>
+<li>The voltage amplifiers are saturating during the measurements (as shown by the LED on figure <a href="#org4499744">1</a>)</li>
+<li>This saturation is mainly due to high frequency noise =&gt; a LPF will be added at the input of the voltage amplifiers in the further measurements</li>
+<li>The measurements will be redone</li>
 </ul>
 
 </div>
@@ -545,406 +569,28 @@ legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-stri
 </div>
 </div>
 
-<div id="outline-container-org6002a8c" class="outline-2">
-<h2 id="org6002a8c"><span class="section-number-2">2</span> Effect of the rotation of the Slip-Ring</h2>
+<div id="outline-container-orga7d54ca" class="outline-2">
+<h2 id="orga7d54ca"><span class="section-number-2">2</span> Measure of the noise induced by the Slip-Ring using voltage amplifiers - Geophone</h2>
 <div class="outline-text-2" id="text-2">
 <p>
-<a id="org953d721"></a>
+<a id="orgc302908"></a>
 </p>
 
-<p>
-The data and matlab files are accessible <a href="data/meas_effect_sr.zip">here</a>.
-</p>
-</div>
-
-<div id="outline-container-orgedc9c11" class="outline-3">
-<h3 id="orgedc9c11"><span class="section-number-3">2.1</span> Measurement Description</h3>
-<div class="outline-text-3" id="text-2-1">
-<p>
-Random Signal is generated by one DAC of the SpeedGoat.
-</p>
-
-<p>
-The signal going out of the DAC is split into two:
-</p>
-<ul class="org-ul">
-<li>one BNC cable is directly connected to one ADC of the SpeedGoat</li>
-<li>one BNC cable goes two times in the Slip-Ring (from bottom to top and then from top to bottom) and then is connected to one ADC of the SpeedGoat</li>
-</ul>
-
-<p>
-Two measurements are done.
-</p>
-<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
-
-
-<colgroup>
-<col  class="org-left" />
-
-<col  class="org-left" />
-</colgroup>
-<thead>
-<tr>
-<th scope="col" class="org-left">Data File</th>
-<th scope="col" class="org-left">Description</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td class="org-left"><code>mat/data_001.mat</code></td>
-<td class="org-left">Slip-ring not turning</td>
-</tr>
-
-<tr>
-<td class="org-left"><code>mat/data_002.mat</code></td>
-<td class="org-left">Slip-ring turning</td>
-</tr>
-</tbody>
-</table>
-
-<p>
-For each measurement, the measured signals are:
-</p>
-<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
-
-
-<colgroup>
-<col  class="org-left" />
-
-<col  class="org-left" />
-</colgroup>
-<thead>
-<tr>
-<th scope="col" class="org-left">Data File</th>
-<th scope="col" class="org-left">Description</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td class="org-left"><code>t</code></td>
-<td class="org-left">Time vector</td>
-</tr>
-
-<tr>
-<td class="org-left"><code>x1</code></td>
-<td class="org-left">Direct signal</td>
-</tr>
-
-<tr>
-<td class="org-left"><code>x2</code></td>
-<td class="org-left">Signal going through the Slip-Ring</td>
-</tr>
-</tbody>
-</table>
-
-<p>
-The goal is to determine is the signal is altered when the spindle is rotating.
-</p>
-
-<p>
-Here, the rotation speed of the Slip-Ring is set to 1rpm.
-</p>
-</div>
-</div>
-
-<div id="outline-container-org5e95fbe" class="outline-3">
-<h3 id="org5e95fbe"><span class="section-number-3">2.2</span> Load data</h3>
-<div class="outline-text-3" id="text-2-2">
-<p>
-We load the data of the z axis of two geophones.
-</p>
-<div class="org-src-container">
-<pre class="src src-matlab">sr_off = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_001.mat', 't', 'x1', 'x2'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-sr_on  = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_002.mat', 't', 'x1', 'x2'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-</pre>
-</div>
-</div>
-</div>
-
-<div id="outline-container-org7a8e8fc" class="outline-3">
-<h3 id="org7a8e8fc"><span class="section-number-3">2.3</span> Analysis</h3>
-<div class="outline-text-3" id="text-2-3">
-<p>
-Let's first look at the signal produced by the DAC (figure <a href="#org340bcf5">4</a>).
-</p>
-
-<div class="org-src-container">
-<pre class="src src-matlab"><span class="org-type">figure</span>;
-hold on;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>sr_on.t,  sr_on.x1<span class="org-rainbow-delimiters-depth-1">)</span>;
-hold off;
-xlabel<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Time </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">s</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">)</span></span><span class="org-string">; ylabel</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">(</span></span><span class="org-string">'Voltage </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">V</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">0</span> <span class="org-highlight-numbers-number">10</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-</pre>
-</div>
-
-
-<div id="org340bcf5" class="figure">
-<p><img src="figs/random_signal.png" alt="random_signal.png" />
-</p>
-<p><span class="figure-number">Figure 4: </span>Random signal produced by the DAC</p>
-</div>
-
-<p>
-We now look at the difference between the signal directly measured by the ADC and the signal that goes through the slip-ring (figure <a href="#org7a50ceb">5</a>).
-</p>
-
-<div class="org-src-container">
-<pre class="src src-matlab"><span class="org-type">figure</span>;
-hold on;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>sr_on.t,  sr_on.x1  <span class="org-type">-</span>  sr_on.x2,  <span class="org-string">'DisplayName', '</span>Slip<span class="org-type">-</span>Ring <span class="org-type">-</span> $<span class="org-type">\</span>omega = <span class="org-highlight-numbers-number">1rpm$</span>'<span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>sr_off.t, sr_off.x1 <span class="org-type">-</span> sr_off.x2,<span class="org-string">'DisplayName', 'Slip-Ring off'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-hold off;
-xlabel<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Time </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">s</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">)</span></span><span class="org-string">; ylabel</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">(</span></span><span class="org-string">'Voltage </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">V</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">0</span> <span class="org-highlight-numbers-number">10</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Location', 'northeast'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-</pre>
-</div>
-
-
-<div id="org7a50ceb" class="figure">
-<p><img src="figs/slipring_comp_signals.png" alt="slipring_comp_signals.png" />
-</p>
-<p><span class="figure-number">Figure 5: </span>Alteration of the signal when the slip-ring is turning</p>
-</div>
-
-<div class="org-src-container">
-<pre class="src src-matlab">dt = sr_on.t<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-1">)</span> <span class="org-type">-</span> sr_on.t<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">1</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-Fs = <span class="org-highlight-numbers-number">1</span><span class="org-type">/</span>dt; <span class="org-comment">% [Hz]</span>
-
-win = hanning<span class="org-rainbow-delimiters-depth-1">(</span>ceil<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-highlight-numbers-number">1</span><span class="org-type">*</span>Fs<span class="org-rainbow-delimiters-depth-2">)</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-</pre>
-</div>
-
-<div class="org-src-container">
-<pre class="src src-matlab"><span class="org-rainbow-delimiters-depth-1">[</span>pxx_on,  f<span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_on.x1  <span class="org-type">-</span> sr_on.x2,  win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
-<span class="org-rainbow-delimiters-depth-1">[</span>pxx_off, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_off.x1 <span class="org-type">-</span> sr_off.x2, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
-</pre>
-</div>
-
-
-<div id="org5986467" class="figure">
-<p><img src="figs/psd_noise.png" alt="psd_noise.png" />
-</p>
-<p><span class="figure-number">Figure 6: </span>ASD of the measured noise</p>
-</div>
-</div>
-</div>
-
-<div id="outline-container-org24db8f6" class="outline-3">
-<h3 id="org24db8f6"><span class="section-number-3">2.4</span> Conclusion</h3>
-<div class="outline-text-3" id="text-2-4">
 <div class="note">
 <p>
-<b>Remaining questions</b>:
-</p>
-<ul class="org-ul">
-<li>Should the measurement be redone using voltage amplifiers?</li>
-<li>Use higher rotation speed and measure for longer periods (to have multiple revolutions) ?</li>
-</ul>
-
-</div>
-</div>
-</div>
-</div>
-<div id="outline-container-org21fc4d2" class="outline-2">
-<h2 id="org21fc4d2"><span class="section-number-2">3</span> Measure of the noise induced by the Slip-Ring</h2>
-<div class="outline-text-2" id="text-3">
-<p>
-<a id="orgddb1e83"></a>
+All the files (data and Matlab scripts) are accessible <a href="data/meas_sr_geophone.zip">here</a>.
 </p>
 
-<p>
-The data and matlab files are accessible <a href="data/meas_slip_ring.zip">here</a>.
-</p>
-</div>
-
-<div id="outline-container-org901cf1f" class="outline-3">
-<h3 id="org901cf1f"><span class="section-number-3">3.1</span> Measurement Description</h3>
-<div class="outline-text-3" id="text-3-1">
-<p>
-<b>Goal</b>:
-</p>
-<ul class="org-ul">
-<li>Determine the noise induced by the slip-ring</li>
-</ul>
-
-<p>
-<b>Setup</b>:
-</p>
-<ul class="org-ul">
-<li>0V is generated by the DAC of the Speedgoat</li>
-<li>Using a T, one part goes directly to the ADC</li>
-<li>The other part goes to the slip-ring 2 times and then to the ADC</li>
-<li>The parameters of the Voltage Amplifier are: 80dB, AC, 1kHz</li>
-<li>Every stage of the station is OFF</li>
-</ul>
-
-<p>
-First column: Direct measure
-Second column: Slip-ring measure
-</p>
-
-
-<p>
-<b>Measurements</b>:
-</p>
-<ul class="org-ul">
-<li><code>data_008</code>: Slip-Ring OFF</li>
-<li><code>data_009</code>: Slip-Ring ON</li>
-<li><code>data_010</code>: Slip-Ring ON and omega=6rpm</li>
-<li><code>data_011</code>: Slip-Ring ON and omega=60rpm</li>
-</ul>
-
-
-<div id="org1e3bbb6" class="figure">
-<p><img src="./img/VID_20190503_160831.gif" alt="VID_20190503_160831.gif" />
-</p>
-<p><span class="figure-number">Figure 7: </span>Slip-Ring rotating at 6rpm</p>
-</div>
-
-
-<div id="orgc9e3e39" class="figure">
-<p><img src="./img/VID_20190503_161401.gif" alt="VID_20190503_161401.gif" />
-</p>
-<p><span class="figure-number">Figure 8: </span>Slip-Ring rotating at 60rpm</p>
-</div>
-</div>
-</div>
-
-<div id="outline-container-org3aa7c6d" class="outline-3">
-<h3 id="org3aa7c6d"><span class="section-number-3">3.2</span> Load data</h3>
-<div class="outline-text-3" id="text-3-2">
-<p>
-We load the data of the z axis of two geophones.
-</p>
-<div class="org-src-container">
-<pre class="src src-matlab">sr_off = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_008.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; sr_off = sr_off.data;
-sr_on  = load<span class="org-rainbow-delimiters-depth-1">(</span>'mat<span class="org-type">/</span>data_009.mat', <span class="org-string">'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; sr_on  = sr_on.data;
-sr_6r  = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_010.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; sr_6r  = sr_6r.data;
-sr_60r = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_011.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; sr_60r = sr_60r.data;
-</pre>
-</div>
-</div>
-</div>
-
-<div id="outline-container-org22f6115" class="outline-3">
-<h3 id="org22f6115"><span class="section-number-3">3.3</span> Time Domain</h3>
-<div class="outline-text-3" id="text-3-3">
-<p>
-We plot the time domain data for the direct measurement (figure <a href="#org841f525">9</a>) and for the signal going through the slip-ring (figure <a href="#orgdc9de69">10</a>);
-</p>
-
-
-<div id="org841f525" class="figure">
-<p><img src="figs/sr_direct_time.png" alt="sr_direct_time.png" />
-</p>
-<p><span class="figure-number">Figure 9: </span>Direct measurement</p>
-</div>
-
-
-
-<div id="orgdc9de69" class="figure">
-<p><img src="figs/sr_slipring_time.png" alt="sr_slipring_time.png" />
-</p>
-<p><span class="figure-number">Figure 10: </span>Measurement of the signal going through the Slip-Ring</p>
-</div>
-</div>
-</div>
-
-<div id="outline-container-orgd6cbe96" class="outline-3">
-<h3 id="orgd6cbe96"><span class="section-number-3">3.4</span> Frequency Domain</h3>
-<div class="outline-text-3" id="text-3-4">
-<p>
-We first compute some parameters that will be used for the PSD computation.
-</p>
-<div class="org-src-container">
-<pre class="src src-matlab">dt = sr_off<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">2</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-1">)</span><span class="org-type">-</span>sr_off<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">1</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-
-Fs = <span class="org-highlight-numbers-number">1</span><span class="org-type">/</span>dt; <span class="org-comment">% [Hz]</span>
-
-win = hanning<span class="org-rainbow-delimiters-depth-1">(</span>ceil<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-highlight-numbers-number">10</span><span class="org-type">*</span>Fs<span class="org-rainbow-delimiters-depth-2">)</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-</pre>
-</div>
-
-<p>
-Then we compute the Power Spectral Density using <code>pwelch</code> function.
-</p>
-<div class="org-src-container">
-<pre class="src src-matlab"><span class="org-rainbow-delimiters-depth-1">[</span>pxdir, f<span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_off<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">1</span><span class="org-rainbow-delimiters-depth-2">)</span>, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
-<span class="org-rainbow-delimiters-depth-1">[</span>pxoff, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_off<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
-<span class="org-rainbow-delimiters-depth-1">[</span>pxon,  <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_on<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>,  win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
-<span class="org-rainbow-delimiters-depth-1">[</span>px6r,  <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_6r<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>,  win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
-<span class="org-rainbow-delimiters-depth-1">[</span>px60r, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_60r<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
-</pre>
-</div>
-
-<p>
-And we plot the ASD of the measured signals (figure <a href="#org70efd75">11</a>);
-</p>
-
-<div class="org-src-container">
-<pre class="src src-matlab"><span class="org-type">figure</span>;
-hold on;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxoff<span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'OFF'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxon<span class="org-rainbow-delimiters-depth-2">)</span>,  <span class="org-string">'DisplayName', 'ON'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>px6r<span class="org-rainbow-delimiters-depth-2">)</span>,  'DisplayName', '<span class="org-highlight-numbers-number">6rpm</span>'<span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>px60r<span class="org-rainbow-delimiters-depth-2">)</span>, 'DisplayName', '<span class="org-highlight-numbers-number">60rpm</span>'<span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxdir<span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'k-', 'DisplayName', 'Direct'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-hold off;
-<span class="org-type">set</span><span class="org-rainbow-delimiters-depth-1">(</span><span class="org-variable-name">gca</span>, <span class="org-string">'xscale', 'log'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-<span class="org-type">set</span><span class="org-rainbow-delimiters-depth-1">(</span><span class="org-variable-name">gca</span>, <span class="org-string">'yscale', 'log'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-xlabel<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Frequency </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">Hz</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">)</span></span><span class="org-string">; ylabel</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">(</span></span><span class="org-string">'</span>ASD of the measured Voltage $<span class="org-type">\</span>left<span class="org-rainbow-delimiters-depth-2">[</span><span class="org-type">\</span>frac<span class="org-rainbow-delimiters-depth-3">{</span>V<span class="org-rainbow-delimiters-depth-3">}{</span><span class="org-type">\</span>sqrt<span class="org-rainbow-delimiters-depth-4">{</span>Hz<span class="org-rainbow-delimiters-depth-4">}</span><span class="org-rainbow-delimiters-depth-3">}</span><span class="org-type">\</span>right<span class="org-rainbow-delimiters-depth-2">]</span>$'<span class="org-rainbow-delimiters-depth-1">)</span>
-legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Location', 'northeast'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">0</span>.<span class="org-highlight-numbers-number">1</span>, <span class="org-highlight-numbers-number">500</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-</pre>
-</div>
-
-
-<div id="org70efd75" class="figure">
-<p><img src="figs/sr_psd_compare.png" alt="sr_psd_compare.png" />
-</p>
-<p><span class="figure-number">Figure 11: </span>Comparison of the ASD of the measured signals when the slip-ring is ON, OFF and turning</p>
-</div>
-</div>
-</div>
-
-<div id="outline-container-orgbb89292" class="outline-3">
-<h3 id="orgbb89292"><span class="section-number-3">3.5</span> Conclusion</h3>
-<div class="outline-text-3" id="text-3-5">
-<div class="important">
-<p>
-<b>Questions:</b>
-</p>
-<ul class="org-ul">
-<li>Why is there some sharp peaks? Can this be due to aliasing?</li>
-<li>It is possible that the amplifiers were saturating during the measurements =&gt; should redo the measurements with a low pass filter before the voltage amplifier</li>
-</ul>
-
-</div>
-</div>
 </div>
 </div>
 
-<div id="outline-container-orgf77f778" class="outline-2">
-<h2 id="orgf77f778"><span class="section-number-2">4</span> Measure of the noise induced by the slip ring when using a geophone</h2>
-<div class="outline-text-2" id="text-4">
-<p>
-<a id="org34dee33"></a>
-</p>
-
-<p>
-The data and matlab files are accessible <a href="data/meas_sr_geophone.zip">here</a>.
-</p>
+<div id="outline-container-org5a59fd1" class="outline-3">
+<h3 id="org5a59fd1"><span class="section-number-3">2.1</span> First Measurement without LPF</h3>
+<div class="outline-text-3" id="text-2-1">
 </div>
-
-<div id="outline-container-org57fc212" class="outline-3">
-<h3 id="org57fc212"><span class="section-number-3">4.1</span> First Measurement without LPF</h3>
-<div class="outline-text-3" id="text-4-1">
-</div>
-<div id="outline-container-org4e633db" class="outline-4">
-<h4 id="org4e633db"><span class="section-number-4">4.1.1</span> Measurement Description</h4>
-<div class="outline-text-4" id="text-4-1-1">
+<div id="outline-container-org9e2424e" class="outline-4">
+<h4 id="org9e2424e"><span class="section-number-4">2.1.1</span> Measurement Description</h4>
+<div class="outline-text-4" id="text-2-1-1">
 <p>
 <b>Goal</b>:
 </p>
@@ -959,35 +605,88 @@ The data and matlab files are accessible <a href="data/meas_sr_geophone.zip">her
 <li>The geophone is located at the sample location</li>
 <li>The two Voltage amplifiers have the same following settings:
 <ul class="org-ul">
-<li>AC</li>
-<li>60dB</li>
-<li>1kHz</li>
+<li>Gain: 60dB</li>
+<li>AC/DC option: AC</li>
+<li>Low pass filter at the output set to 1kHz</li>
 </ul></li>
 <li>The signal from the geophone is split into two using a T-BNC:
 <ul class="org-ul">
-<li>One part goes directly to the voltage amplifier and then to the ADC.</li>
-<li>The other part goes to the slip-ring=&gt;voltage amplifier=&gt;ADC.</li>
+<li>One part goes directly to the voltage amplifier and then to the ADC</li>
+<li>The other part goes to the slip-ring=&gt;voltage amplifier=&gt;ADC</li>
 </ul></li>
 </ul>
 
 <p>
-First column: Direct measure
-Second column: Slip-ring measure
+<b>Measurements</b>:
+Two measurements are done:
 </p>
+<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
+
+
+<colgroup>
+<col  class="org-left" />
+
+<col  class="org-left" />
+</colgroup>
+<thead>
+<tr>
+<th scope="col" class="org-left">Measurement File</th>
+<th scope="col" class="org-left">Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="org-left"><code>data_012</code></td>
+<td class="org-left">Slip-Ring OFF</td>
+</tr>
+
+<tr>
+<td class="org-left"><code>data_013</code></td>
+<td class="org-left">Slip-Ring ON</td>
+</tr>
+</tbody>
+</table>
 
 <p>
-<b>Measurements</b>:
+Each of the measurement <code>mat</code> file contains one <code>data</code> array with 3 columns:
 </p>
-<ul class="org-ul">
-<li><code>data_012</code>: Slip-Ring OFF</li>
-<li><code>data_013</code>: Slip-Ring ON</li>
-</ul>
+<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
+
+
+<colgroup>
+<col  class="org-right" />
+
+<col  class="org-left" />
+</colgroup>
+<thead>
+<tr>
+<th scope="col" class="org-right">Column number</th>
+<th scope="col" class="org-left">Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="org-right">1</td>
+<td class="org-left">Measure of the geophone at the sample position with a direct wire</td>
+</tr>
+
+<tr>
+<td class="org-right">2</td>
+<td class="org-left">Measure of the geophone at the sample position going through the slip-ring</td>
+</tr>
+
+<tr>
+<td class="org-right">3</td>
+<td class="org-left">Time</td>
+</tr>
+</tbody>
+</table>
 </div>
 </div>
 
-<div id="outline-container-orge652945" class="outline-4">
-<h4 id="orge652945"><span class="section-number-4">4.1.2</span> Load data</h4>
-<div class="outline-text-4" id="text-4-1-2">
+<div id="outline-container-org1dd1ac5" class="outline-4">
+<h4 id="org1dd1ac5"><span class="section-number-4">2.1.2</span> Load data</h4>
+<div class="outline-text-4" id="text-2-1-2">
 <p>
 We load the data of the z axis of two geophones.
 </p>
@@ -999,32 +698,32 @@ sr_on  = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="o
 </div>
 </div>
 
-<div id="outline-container-orgfdc44bc" class="outline-4">
-<h4 id="orgfdc44bc"><span class="section-number-4">4.1.3</span> Time Domain</h4>
-<div class="outline-text-4" id="text-4-1-3">
+<div id="outline-container-orgf20d3eb" class="outline-4">
+<h4 id="orgf20d3eb"><span class="section-number-4">2.1.3</span> Time Domain</h4>
+<div class="outline-text-4" id="text-2-1-3">
 <p>
-We compare the signal when the Slip-Ring is OFF (figure <a href="#org2b29bbb">12</a>) and when it is ON (figure <a href="#org0c98be5">13</a>).
+We compare the signal when the Slip-Ring is OFF (figure <a href="#orga601ddd">4</a>) and when it is ON (figure <a href="#org5bd7dab">5</a>).
 </p>
 
 
-<div id="org2b29bbb" class="figure">
+<div id="orga601ddd" class="figure">
 <p><img src="figs/sr_geophone_time_off.png" alt="sr_geophone_time_off.png" />
 </p>
-<p><span class="figure-number">Figure 12: </span>Comparison of the time domain signals when the slip-ring is OFF</p>
+<p><span class="figure-number">Figure 4: </span>Comparison of the time domain signals when the slip-ring is OFF</p>
 </div>
 
 
-<div id="org0c98be5" class="figure">
+<div id="org5bd7dab" class="figure">
 <p><img src="figs/sr_geophone_time_on.png" alt="sr_geophone_time_on.png" />
 </p>
-<p><span class="figure-number">Figure 13: </span>Comparison of the time domain signals when the slip-ring is ON</p>
+<p><span class="figure-number">Figure 5: </span>Comparison of the time domain signals when the slip-ring is ON</p>
 </div>
 </div>
 </div>
 
-<div id="outline-container-org1747240" class="outline-4">
-<h4 id="org1747240"><span class="section-number-4">4.1.4</span> Frequency Domain</h4>
-<div class="outline-text-4" id="text-4-1-4">
+<div id="outline-container-orge85c7f5" class="outline-4">
+<h4 id="orge85c7f5"><span class="section-number-4">2.1.4</span> Frequency Domain</h4>
+<div class="outline-text-4" id="text-2-1-4">
 <p>
 We first compute some parameters that will be used for the PSD computation.
 </p>
@@ -1052,7 +751,7 @@ Then we compute the Power Spectral Density using <code>pwelch</code> function.
 </div>
 
 <p>
-Finally, we compare the Amplitude Spectral Density of the signals (figure <a href="#org6f7187f">14</a>);
+Finally, we compare the Amplitude Spectral Density of the signals (figure <a href="#orgebf0258">6</a>);
 </p>
 
 <div class="org-src-container">
@@ -1072,36 +771,36 @@ xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbo
 </div>
 
 
-<div id="org6f7187f" class="figure">
+<div id="orgebf0258" class="figure">
 <p><img src="figs/sr_geophone_asd.png" alt="sr_geophone_asd.png" />
 </p>
-<p><span class="figure-number">Figure 14: </span>Comparison of the Amplitude Spectral Sensity</p>
+<p><span class="figure-number">Figure 6: </span>Comparison of the Amplitude Spectral Sensity</p>
 </div>
 
 
-<div id="orgacb2d5e" class="figure">
+<div id="org1c275ed" class="figure">
 <p><img src="figs/sr_geophone_asd_zoom.png" alt="sr_geophone_asd_zoom.png" />
 </p>
-<p><span class="figure-number">Figure 15: </span>Comparison of the Amplitude Spectral Sensity - Zoom</p>
+<p><span class="figure-number">Figure 7: </span>Comparison of the Amplitude Spectral Sensity - Zoom</p>
 </div>
 </div>
 </div>
 
-<div id="outline-container-org2082a3e" class="outline-4">
-<h4 id="org2082a3e"><span class="section-number-4">4.1.5</span> Conclusion</h4>
-<div class="outline-text-4" id="text-4-1-5">
+<div id="outline-container-orgdf83e7e" class="outline-4">
+<h4 id="orgdf83e7e"><span class="section-number-4">2.1.5</span> Conclusion</h4>
+<div class="outline-text-4" id="text-2-1-5">
 <div class="important">
 <ul class="org-ul">
-<li>The fact that the Slip-Ring is turned ON adds some noise to the signal.</li>
-<li>The signal going through the Slip-Ring is less noisy than the one going directly to the ADC.</li>
-<li>This could be due to less good electromagnetic isolation.</li>
+<li>The fact that the Slip-Ring is turned ON adds some noise to the signals</li>
+<li>The signal going through the Slip-Ring is less noisy than the one going directly to the ADC</li>
+<li>This could be due to better electromagnetic isolation in the slip-ring</li>
 </ul>
 
 <p>
 <b>Questions</b>:
 </p>
 <ul class="org-ul">
-<li>Can the sharp peak on figure <a href="#orgacb2d5e">15</a> be due to the Aliasing?</li>
+<li>Can the sharp peak on figure <a href="#org1c275ed">7</a> be due to the Aliasing?</li>
 </ul>
 
 </div>
@@ -1109,49 +808,49 @@ xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbo
 </div>
 </div>
 
-<div id="outline-container-org0d10493" class="outline-3">
-<h3 id="org0d10493"><span class="section-number-3">4.2</span> Measurement using an oscilloscope</h3>
-<div class="outline-text-3" id="text-4-2">
+<div id="outline-container-org0687474" class="outline-3">
+<h3 id="org0687474"><span class="section-number-3">2.2</span> Measurement using an oscilloscope</h3>
+<div class="outline-text-3" id="text-2-2">
 </div>
-<div id="outline-container-org84a4af9" class="outline-4">
-<h4 id="org84a4af9"><span class="section-number-4">4.2.1</span> Measurement Setup</h4>
-<div class="outline-text-4" id="text-4-2-1">
+<div id="outline-container-org8d0ea64" class="outline-4">
+<h4 id="org8d0ea64"><span class="section-number-4">2.2.1</span> Measurement Setup</h4>
+<div class="outline-text-4" id="text-2-2-1">
 <p>
-Know we are measuring the same signals but using an oscilloscope instead of the Speedgoat ADC.
+We are now measuring the same signals than in the previous section, but with an oscilloscope instead of with the Speedgoat ADC.
 </p>
 </div>
 </div>
 
-<div id="outline-container-orgba2e6ff" class="outline-4">
-<h4 id="orgba2e6ff"><span class="section-number-4">4.2.2</span> Observations</h4>
-<div class="outline-text-4" id="text-4-2-2">
+<div id="outline-container-orgf090bd6" class="outline-4">
+<h4 id="orgf090bd6"><span class="section-number-4">2.2.2</span> Observations</h4>
+<div class="outline-text-4" id="text-2-2-2">
 <p>
-Then the Slip-Ring is ON (figure <a href="#org8cbaa23">16</a>), we observe a signal at 40kHz with a peak-to-peak amplitude of 200mV for the direct measure and 100mV for the signal going through the Slip-Ring.
+Then the Slip-Ring is ON (figure <a href="#orgb291d11">8</a>), we observe a signal at 40kHz with a peak-to-peak amplitude of 200mV for the direct measure and 100mV for the signal going through the Slip-Ring.
 </p>
 
 <p>
-Then the Slip-Ring is OFF, we don't observe this 40kHz anymore (figure <a href="#orgeeac555">17</a>).
+Then the Slip-Ring is OFF, we don't observe this noise at 40kHz anymore (figure <a href="#org1fc4755">9</a>).
 </p>
 
 
-<div id="org8cbaa23" class="figure">
+<div id="orgb291d11" class="figure">
 <p><img src="./img/IMG_20190506_160420.jpg" alt="IMG_20190506_160420.jpg" width="500px" />
 </p>
-<p><span class="figure-number">Figure 16: </span>Signals measured by the oscilloscope - Slip-Ring ON - Yellow: Direct measure - Blue: Through Slip-Ring</p>
+<p><span class="figure-number">Figure 8: </span>Signals measured by the oscilloscope - Slip-Ring ON - Yellow: Direct measure - Blue: Through Slip-Ring</p>
 </div>
 
 
-<div id="orgeeac555" class="figure">
+<div id="org1fc4755" class="figure">
 <p><img src="./img/IMG_20190506_160438.jpg" alt="IMG_20190506_160438.jpg" width="500px" />
 </p>
-<p><span class="figure-number">Figure 17: </span>Signals measured by the oscilloscope - Slip-Ring OFF - Yellow: Direct measure - Blue: Through Slip-Ring</p>
+<p><span class="figure-number">Figure 9: </span>Signals measured by the oscilloscope - Slip-Ring OFF - Yellow: Direct measure - Blue: Through Slip-Ring</p>
 </div>
 </div>
 </div>
 
-<div id="outline-container-org729aaf2" class="outline-4">
-<h4 id="org729aaf2"><span class="section-number-4">4.2.3</span> Conclusion</h4>
-<div class="outline-text-4" id="text-4-2-3">
+<div id="outline-container-org8d48fa3" class="outline-4">
+<h4 id="org8d48fa3"><span class="section-number-4">2.2.3</span> Conclusion</h4>
+<div class="outline-text-4" id="text-2-2-3">
 <div class="important">
 <ul class="org-ul">
 <li>By looking at the signals using an oscilloscope, there is a lot of high frequency noise when turning on the Slip-Ring</li>
@@ -1164,15 +863,35 @@ Then the Slip-Ring is OFF, we don't observe this 40kHz anymore (figure <a href="
 </div>
 </div>
 
-<div id="outline-container-orge6ed6b4" class="outline-3">
-<h3 id="orge6ed6b4"><span class="section-number-3">4.3</span> New measurements with a LPF before the Voltage Amplifiers</h3>
-<div class="outline-text-3" id="text-4-3">
+<div id="outline-container-org09cd59c" class="outline-3">
+<h3 id="org09cd59c"><span class="section-number-3">2.3</span> New measurements with a LPF before the Voltage Amplifiers</h3>
+<div class="outline-text-3" id="text-2-3">
 </div>
-<div id="outline-container-org4501bcc" class="outline-4">
-<h4 id="org4501bcc"><span class="section-number-4">4.3.1</span> Setup description</h4>
-<div class="outline-text-4" id="text-4-3-1">
+<div id="outline-container-org36fc63d" class="outline-4">
+<h4 id="org36fc63d"><span class="section-number-4">2.3.1</span> Setup description</h4>
+<div class="outline-text-4" id="text-2-3-1">
 <p>
-A first order low pass filter is added before the Voltage Amplifiers with the following values:
+<b>Goal</b>:
+The goal is to see if we can remove high frequency noise from the signals before the voltage amplifiers in order to not saturate them.
+</p>
+
+<p>
+<b>Setup</b>:
+We are measuring the signal from a geophone put at the sample position.
+Using a BNC slitter, one part is going directly to the Low pass filter, voltage amplifier and ADC (first column), the other part is going through the slip ring before the low pass filter and the voltage amplifier (second column).
+</p>
+
+<p>
+The two voltage amplifiers have the same following settings:
+</p>
+<ul class="org-ul">
+<li>Gain: 60dB</li>
+<li>AC/DC option: DC</li>
+<li>Low pass filter at the output set to 1kHz</li>
+</ul>
+
+<p>
+The low pass filter is a first order low pass filter RC circuit. It is added before the Voltage Amplifiers and has the following values:
 </p>
 \begin{aligned}
   R &= 1k\Omega \\
@@ -1180,22 +899,80 @@ A first order low pass filter is added before the Voltage Amplifiers with the fo
 \end{aligned}
 
 <p>
-And we have a cut-off frequency of \(f_c = \frac{1}{RC} = 160Hz\).
+And the cut-off frequency is \(f_c = \frac{1}{RC} = 160Hz\).
 </p>
 
 <p>
-We are measuring the signal from a geophone put on the marble with and without the added LPF:
+<b>Measurements</b>:
+Two measurements are done:
 </p>
-<ul class="org-ul">
-<li>with the slip ring OFF: <code>mat/data_016.mat</code></li>
-<li>with the slip ring ON: <code>mat/data_017.mat</code></li>
-</ul>
+<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
+
+
+<colgroup>
+<col  class="org-left" />
+
+<col  class="org-left" />
+</colgroup>
+<thead>
+<tr>
+<th scope="col" class="org-left">Measurement File</th>
+<th scope="col" class="org-left">Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="org-left"><code>mat/data_016.mat</code></td>
+<td class="org-left">Signal from the geophone at the sample location - Slip-Ring OFF</td>
+</tr>
+
+<tr>
+<td class="org-left"><code>mat/data_017.mat</code></td>
+<td class="org-left">Signal from the geophone at the sample location - Slip-Ring ON</td>
+</tr>
+</tbody>
+</table>
+
+<p>
+Each of the measurement <code>mat</code> file contains one <code>data</code> array with 3 columns:
+</p>
+<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
+
+
+<colgroup>
+<col  class="org-right" />
+
+<col  class="org-left" />
+</colgroup>
+<thead>
+<tr>
+<th scope="col" class="org-right">Column number</th>
+<th scope="col" class="org-left">Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="org-right">1</td>
+<td class="org-left">Direct measurement</td>
+</tr>
+
+<tr>
+<td class="org-right">2</td>
+<td class="org-left">Signal going through the slip-ring</td>
+</tr>
+
+<tr>
+<td class="org-right">3</td>
+<td class="org-left">Time</td>
+</tr>
+</tbody>
+</table>
 </div>
 </div>
 
-<div id="outline-container-org7f64f45" class="outline-4">
-<h4 id="org7f64f45"><span class="section-number-4">4.3.2</span> Load data</h4>
-<div class="outline-text-4" id="text-4-3-2">
+<div id="outline-container-org7823df0" class="outline-4">
+<h4 id="org7823df0"><span class="section-number-4">2.3.2</span> Load data</h4>
+<div class="outline-text-4" id="text-2-3-2">
 <p>
 We load the data of the z axis of two geophones.
 </p>
@@ -1207,32 +984,32 @@ sr_lpf_on  = load<span class="org-rainbow-delimiters-depth-1">(</span><span clas
 </div>
 </div>
 
-<div id="outline-container-org168648f" class="outline-4">
-<h4 id="org168648f"><span class="section-number-4">4.3.3</span> Time Domain</h4>
-<div class="outline-text-4" id="text-4-3-3">
+<div id="outline-container-orga0f3ca7" class="outline-4">
+<h4 id="orga0f3ca7"><span class="section-number-4">2.3.3</span> Time Domain</h4>
+<div class="outline-text-4" id="text-2-3-3">
 <p>
-We compare the signal when the Slip-Ring is OFF (figure <a href="#org82abb68">18</a>) and when it is ON (figure <a href="#org7701819">19</a>).
+We compare the signal when the Slip-Ring is OFF (figure <a href="#org7614cda">10</a>) and when it is ON (figure <a href="#org7afe5f1">11</a>).
 </p>
 
 
-<div id="org82abb68" class="figure">
+<div id="org7614cda" class="figure">
 <p><img src="figs/sr_lpf_geophone_time_off.png" alt="sr_lpf_geophone_time_off.png" />
 </p>
-<p><span class="figure-number">Figure 18: </span>Comparison of the time domain signals when the slip-ring is OFF</p>
+<p><span class="figure-number">Figure 10: </span>Comparison of the time domain signals when the slip-ring is OFF</p>
 </div>
 
 
-<div id="org7701819" class="figure">
+<div id="org7afe5f1" class="figure">
 <p><img src="figs/sr_lpf_geophone_time_on.png" alt="sr_lpf_geophone_time_on.png" />
 </p>
-<p><span class="figure-number">Figure 19: </span>Comparison of the time domain signals when the slip-ring is ON</p>
+<p><span class="figure-number">Figure 11: </span>Comparison of the time domain signals when the slip-ring is ON</p>
 </div>
 </div>
 </div>
 
-<div id="outline-container-org18b3f68" class="outline-4">
-<h4 id="org18b3f68"><span class="section-number-4">4.3.4</span> Frequency Domain</h4>
-<div class="outline-text-4" id="text-4-3-4">
+<div id="outline-container-org3a55406" class="outline-4">
+<h4 id="org3a55406"><span class="section-number-4">2.3.4</span> Frequency Domain</h4>
+<div class="outline-text-4" id="text-2-3-4">
 <p>
 We first compute some parameters that will be used for the PSD computation.
 </p>
@@ -1260,51 +1037,484 @@ Then we compute the Power Spectral Density using <code>pwelch</code> function.
 </div>
 
 <p>
-Finally, we compare the Amplitude Spectral Density of the signals (figure <a href="#org58407c0">20</a>);
+Finally, we compare the Amplitude Spectral Density of the signals (figure <a href="#org62c4aa2">12</a>);
 </p>
 
 <div class="org-src-container">
 <pre class="src src-matlab"><span class="org-type">figure</span>;
 hold on;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxd_lpf_off<span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'Direct - OFF'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxd_lpf_off<span class="org-rainbow-delimiters-depth-2">)</span>,  <span class="org-string">'DisplayName', 'Direct - OFF'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxsr_lpf_off<span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'Slip-Ring - OFF'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxd_lpf_on<span class="org-rainbow-delimiters-depth-2">)</span>,  <span class="org-string">'DisplayName', 'Direct - ON'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxd_lpf_on<span class="org-rainbow-delimiters-depth-2">)</span>,   <span class="org-string">'DisplayName', 'Direct - ON'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxsr_lpf_on<span class="org-rainbow-delimiters-depth-2">)</span>,  <span class="org-string">'DisplayName', 'Slip-Ring - ON'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 hold off;
-<span class="org-type">set</span><span class="org-rainbow-delimiters-depth-1">(</span><span class="org-variable-name">gca</span>, <span class="org-string">'xscale', 'log'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-<span class="org-type">set</span><span class="org-rainbow-delimiters-depth-1">(</span><span class="org-variable-name">gca</span>, <span class="org-string">'yscale', 'log'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-xlabel<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Frequency </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">Hz</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">)</span></span><span class="org-string">; ylabel</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">(</span></span><span class="org-string">'</span>ASD of the measured Voltage $<span class="org-type">\</span>left<span class="org-rainbow-delimiters-depth-2">[</span><span class="org-type">\</span>frac<span class="org-rainbow-delimiters-depth-3">{</span>V<span class="org-rainbow-delimiters-depth-3">}{</span><span class="org-type">\</span>sqrt<span class="org-rainbow-delimiters-depth-4">{</span>Hz<span class="org-rainbow-delimiters-depth-4">}</span><span class="org-rainbow-delimiters-depth-3">}</span><span class="org-type">\</span>right<span class="org-rainbow-delimiters-depth-2">]</span>$'<span class="org-rainbow-delimiters-depth-1">)</span>
-legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Location', 'northeast'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">0</span>.<span class="org-highlight-numbers-number">1</span>, <span class="org-highlight-numbers-number">500</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+<span class="org-type">set</span><span class="org-rainbow-delimiters-depth-1">(</span><span class="org-variable-name">gca</span>, <span class="org-string">'xscale', 'log'</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">)</span></span><span class="org-string">; set</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">(</span></span><span class="org-string">gca, 'yscale', 'log'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+xlabel<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Frequency </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">Hz</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">)</span></span><span class="org-string">; ylabel</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">(</span></span><span class="org-string">'</span>ASD of the measured Voltage $<span class="org-type">\</span>left<span class="org-rainbow-delimiters-depth-2">[</span><span class="org-type">\</span>frac<span class="org-rainbow-delimiters-depth-3">{</span>V<span class="org-rainbow-delimiters-depth-3">}{</span><span class="org-type">\</span>sqrt<span class="org-rainbow-delimiters-depth-4">{</span>Hz<span class="org-rainbow-delimiters-depth-4">}</span><span class="org-rainbow-delimiters-depth-3">}</span><span class="org-type">\</span>right<span class="org-rainbow-delimiters-depth-2">]</span>$'<span class="org-rainbow-delimiters-depth-1">)</span>
+legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Location', 'soutwest'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 </pre>
 </div>
 
 
-<div id="org58407c0" class="figure">
+<div id="org62c4aa2" class="figure">
 <p><img src="figs/sr_lpf_geophone_asd.png" alt="sr_lpf_geophone_asd.png" />
 </p>
-<p><span class="figure-number">Figure 20: </span>Comparison of the Amplitude Spectral Sensity</p>
+<p><span class="figure-number">Figure 12: </span>Comparison of the Amplitude Spectral Sensity</p>
 </div>
 
 
-<div id="orge9dc071" class="figure">
+<div id="org9f79309" class="figure">
 <p><img src="figs/sr_lpf_geophone_asd_zoom.png" alt="sr_lpf_geophone_asd_zoom.png" />
 </p>
-<p><span class="figure-number">Figure 21: </span>Comparison of the Amplitude Spectral Sensity - Zoom</p>
+<p><span class="figure-number">Figure 13: </span>Comparison of the Amplitude Spectral Sensity - Zoom</p>
 </div>
 </div>
 </div>
 
-<div id="outline-container-org5c54c76" class="outline-4">
-<h4 id="org5c54c76"><span class="section-number-4">4.3.5</span> Comparison of with and without LPF</h4>
-<div class="outline-text-4" id="text-4-3-5">
+<div id="outline-container-orgf462896" class="outline-4">
+<h4 id="orgf462896"><span class="section-number-4">2.3.5</span> Conclusion</h4>
+<div class="outline-text-4" id="text-2-3-5">
+<div class="important">
+<ul class="org-ul">
+<li>Using the LPF, we don't see any additional noise coming from the slip-ring when it is turned ON</li>
+<li>However, we should use a smaller value of the capacitor to have a cut-off frequency at \(1kHz\)</li>
+<li>We here observe a signal at \(50Hz\) and its harmonics</li>
+</ul>
+
+</div>
+</div>
+</div>
+</div>
+
+<div id="outline-container-orgfc76b2a" class="outline-3">
+<h3 id="orgfc76b2a"><span class="section-number-3">2.4</span> <span class="todo TODO">TODO</span> New LPF at 1kHz</h3>
+</div>
+</div>
+<div id="outline-container-orgf6fc986" class="outline-2">
+<h2 id="orgf6fc986"><span class="section-number-2">3</span> Effect of the rotation of the Slip-Ring - Noise</h2>
+<div class="outline-text-2" id="text-3">
+<p>
+<a id="org013f23a"></a>
+</p>
+
+<div class="note">
+<p>
+All the files (data and Matlab scripts) are accessible <a href="data/meas_effect_sr.zip">here</a>.
+</p>
+
+</div>
+</div>
+
+<div id="outline-container-orgf659e9b" class="outline-3">
+<h3 id="orgf659e9b"><span class="section-number-3">3.1</span> Measurement Description</h3>
+<div class="outline-text-3" id="text-3-1">
+<p>
+<b>Goal</b>:
+The goal is to determine if the signal is altered when the spindle is rotating.
+</p>
+
+
+<p>
+<b>Setup</b>:
+Random Signal is generated by one SpeedGoat DAC.
+</p>
+
+<p>
+The signal going out of the DAC is split into two:
+</p>
+<ul class="org-ul">
+<li>one BNC cable is directly connected to one ADC of the SpeedGoat</li>
+<li>one BNC cable goes two times in the Slip-Ring (from bottom to top and then from top to bottom) and then is connected to one ADC of the SpeedGoat</li>
+</ul>
+
+<p>
+All the stages are turned OFF except the Slip-Ring.
+</p>
+
+
+<p>
+<b>Measurements</b>:
+</p>
+<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
+
+
+<colgroup>
+<col  class="org-left" />
+
+<col  class="org-left" />
+</colgroup>
+<thead>
+<tr>
+<th scope="col" class="org-left">Data File</th>
+<th scope="col" class="org-left">Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="org-left"><code>mat/data_001.mat</code></td>
+<td class="org-left">Slip-ring not turning but ON</td>
+</tr>
+
+<tr>
+<td class="org-left"><code>mat/data_002.mat</code></td>
+<td class="org-left">Slip-ring turning at 1rpm</td>
+</tr>
+</tbody>
+</table>
+
+<p>
+For each measurement, the measured signals are:
+</p>
+<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
+
+
+<colgroup>
+<col  class="org-left" />
+
+<col  class="org-left" />
+</colgroup>
+<thead>
+<tr>
+<th scope="col" class="org-left">Variable</th>
+<th scope="col" class="org-left">Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="org-left"><code>t</code></td>
+<td class="org-left">Time vector</td>
+</tr>
+
+<tr>
+<td class="org-left"><code>x1</code></td>
+<td class="org-left">Direct signal</td>
+</tr>
+
+<tr>
+<td class="org-left"><code>x2</code></td>
+<td class="org-left">Signal going through the Slip-Ring</td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+
+<div id="outline-container-orgee42249" class="outline-3">
+<h3 id="orgee42249"><span class="section-number-3">3.2</span> Load data</h3>
+<div class="outline-text-3" id="text-3-2">
+<p>
+We load the data of the z axis of two geophones.
+</p>
+<div class="org-src-container">
+<pre class="src src-matlab">sr_off = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_001.mat', 't', 'x1', 'x2'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+sr_on  = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_002.mat', 't', 'x1', 'x2'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+</pre>
+</div>
+</div>
+</div>
+
+<div id="outline-container-org5ba0b07" class="outline-3">
+<h3 id="org5ba0b07"><span class="section-number-3">3.3</span> Analysis</h3>
+<div class="outline-text-3" id="text-3-3">
+<p>
+Let's first look at the signal produced by the DAC (figure <a href="#orge517e79">14</a>).
+</p>
+
 <div class="org-src-container">
 <pre class="src src-matlab"><span class="org-type">figure</span>;
 hold on;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxdon<span class="org-rainbow-delimiters-depth-2">)</span>,  <span class="org-string">'DisplayName', 'Direct - ON'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxsron<span class="org-rainbow-delimiters-depth-2">)</span>,  <span class="org-string">'DisplayName', 'Slip-Ring - ON'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxd_lpf_on<span class="org-rainbow-delimiters-depth-2">)</span>,  <span class="org-string">'DisplayName', 'Direct - ON - LPF'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
-plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxsr_lpf_on<span class="org-rainbow-delimiters-depth-2">)</span>,  <span class="org-string">'DisplayName', 'Slip-Ring - ON - LPF'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>sr_on.t,  sr_on.x1<span class="org-rainbow-delimiters-depth-1">)</span>;
+hold off;
+xlabel<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Time </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">s</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">)</span></span><span class="org-string">; ylabel</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">(</span></span><span class="org-string">'Voltage </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">V</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">0</span> <span class="org-highlight-numbers-number">10</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+</pre>
+</div>
+
+
+<div id="orge517e79" class="figure">
+<p><img src="figs/random_signal.png" alt="random_signal.png" />
+</p>
+<p><span class="figure-number">Figure 14: </span>Random signal produced by the DAC</p>
+</div>
+
+<p>
+We now look at the difference between the signal directly measured by the ADC and the signal that goes through the slip-ring (figure <a href="#org3a3b2d6">15</a>).
+</p>
+
+<div class="org-src-container">
+<pre class="src src-matlab"><span class="org-type">figure</span>;
+hold on;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>sr_on.t,  sr_on.x1  <span class="org-type">-</span>  sr_on.x2,  <span class="org-string">'DisplayName', '</span>Slip<span class="org-type">-</span>Ring <span class="org-type">-</span> $<span class="org-type">\</span>omega = <span class="org-highlight-numbers-number">1rpm$</span>'<span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>sr_off.t, sr_off.x1 <span class="org-type">-</span> sr_off.x2,<span class="org-string">'DisplayName', 'Slip-Ring off'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+hold off;
+xlabel<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Time </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">s</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">)</span></span><span class="org-string">; ylabel</span><span class="org-string"><span class="org-rainbow-delimiters-depth-1">(</span></span><span class="org-string">'Voltage </span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">[</span></span><span class="org-string">V</span><span class="org-string"><span class="org-rainbow-delimiters-depth-2">]</span></span><span class="org-string">'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">0</span> <span class="org-highlight-numbers-number">10</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'Location', 'northeast'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+</pre>
+</div>
+
+
+<div id="org3a3b2d6" class="figure">
+<p><img src="figs/slipring_comp_signals.png" alt="slipring_comp_signals.png" />
+</p>
+<p><span class="figure-number">Figure 15: </span>Alteration of the signal when the slip-ring is turning</p>
+</div>
+
+<div class="org-src-container">
+<pre class="src src-matlab">dt = sr_on.t<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-1">)</span> <span class="org-type">-</span> sr_on.t<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">1</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+Fs = <span class="org-highlight-numbers-number">1</span><span class="org-type">/</span>dt; <span class="org-comment">% [Hz]</span>
+
+win = hanning<span class="org-rainbow-delimiters-depth-1">(</span>ceil<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-highlight-numbers-number">1</span><span class="org-type">*</span>Fs<span class="org-rainbow-delimiters-depth-2">)</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+</pre>
+</div>
+
+<div class="org-src-container">
+<pre class="src src-matlab"><span class="org-rainbow-delimiters-depth-1">[</span>pxx_on,  f<span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_on.x1  <span class="org-type">-</span> sr_on.x2,  win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
+<span class="org-rainbow-delimiters-depth-1">[</span>pxx_off, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_off.x1 <span class="org-type">-</span> sr_off.x2, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
+</pre>
+</div>
+
+
+<div id="org0c182a5" class="figure">
+<p><img src="figs/psd_noise.png" alt="psd_noise.png" />
+</p>
+<p><span class="figure-number">Figure 16: </span>ASD of the measured noise</p>
+</div>
+</div>
+</div>
+
+<div id="outline-container-org164ce5f" class="outline-3">
+<h3 id="org164ce5f"><span class="section-number-3">3.4</span> Conclusion</h3>
+<div class="outline-text-3" id="text-3-4">
+<div class="note">
+<ul class="org-ul">
+<li>The measurement is mostly limited by the resolution of the Speedgoat DAC (16bits over \(\pm 10 V\))</li>
+<li>In section <a href="#orgf911c37">4</a>, the same measurement is done but voltage amplifiers are added to amplify the noise</li>
+</ul>
+
+</div>
+</div>
+</div>
+</div>
+
+<div id="outline-container-org88023e5" class="outline-2">
+<h2 id="org88023e5"><span class="section-number-2">4</span> Measure of the noise induced by the Slip-Ring using voltage amplifiers - Noise</h2>
+<div class="outline-text-2" id="text-4">
+<p>
+<a id="orgf911c37"></a>
+</p>
+
+<div class="note">
+<p>
+All the files (data and Matlab scripts) are accessible <a href="data/meas_slip_ring.zip">here</a>.
+</p>
+
+</div>
+</div>
+
+<div id="outline-container-org89e519f" class="outline-3">
+<h3 id="org89e519f"><span class="section-number-3">4.1</span> Measurement Description</h3>
+<div class="outline-text-3" id="text-4-1">
+<p>
+<b>Goal</b>:
+</p>
+<ul class="org-ul">
+<li>Determine the noise induced by the slip-ring when turned ON and when rotating</li>
+</ul>
+
+
+<p>
+<b>Setup</b>:
+</p>
+<ul class="org-ul">
+<li>0V is generated by one Speedgoat DAC</li>
+<li>Using a T, one part goes directly to one Speedgoat ADC</li>
+<li>The other part goes to the slip-ring 2 times and then to one voltage amplifier before going to the ADC</li>
+<li>The parameters of the Voltage Amplifier are:
+<ul class="org-ul">
+<li>gain of 80dB</li>
+<li>AC/DC option to AC (it adds an high pass filter at 1.5Hz at the input of the voltage amplifier)</li>
+<li>Output Low pass filter set at 1kHz</li>
+</ul></li>
+<li>Every stage of the station is OFF</li>
+</ul>
+
+<p>
+First column: Direct measure
+Second column: Slip-ring measure
+</p>
+
+
+<p>
+<b>Measurements</b>:
+</p>
+<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
+
+
+<colgroup>
+<col  class="org-left" />
+
+<col  class="org-left" />
+</colgroup>
+<thead>
+<tr>
+<th scope="col" class="org-left">Data File</th>
+<th scope="col" class="org-left">Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="org-left"><code>mat/data_008.mat</code></td>
+<td class="org-left">Slip-Ring OFF</td>
+</tr>
+
+<tr>
+<td class="org-left"><code>mat/data_009.mat</code></td>
+<td class="org-left">Slip-Ring ON</td>
+</tr>
+
+<tr>
+<td class="org-left"><code>mat/data_010.mat</code></td>
+<td class="org-left">Slip-Ring ON and omega=6rpm</td>
+</tr>
+
+<tr>
+<td class="org-left"><code>mat/data_011.mat</code></td>
+<td class="org-left">Slip-Ring ON and omega=60rpm</td>
+</tr>
+</tbody>
+</table>
+
+<p>
+Each of the measurement <code>mat</code> file contains one <code>data</code> array with 3 columns:
+</p>
+<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
+
+
+<colgroup>
+<col  class="org-right" />
+
+<col  class="org-left" />
+</colgroup>
+<thead>
+<tr>
+<th scope="col" class="org-right">Column number</th>
+<th scope="col" class="org-left">Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="org-right">1</td>
+<td class="org-left">Signal going directly to the ADC</td>
+</tr>
+
+<tr>
+<td class="org-right">2</td>
+<td class="org-left">Signal going through the Slip-Ring</td>
+</tr>
+
+<tr>
+<td class="org-right">3</td>
+<td class="org-left">Time</td>
+</tr>
+</tbody>
+</table>
+
+
+<div id="orgc3d4209" class="figure">
+<p><img src="./img/VID_20190503_160831.gif" alt="VID_20190503_160831.gif" />
+</p>
+<p><span class="figure-number">Figure 17: </span>Slip-Ring rotating at 6rpm</p>
+</div>
+
+
+<div id="org489322f" class="figure">
+<p><img src="./img/VID_20190503_161401.gif" alt="VID_20190503_161401.gif" />
+</p>
+<p><span class="figure-number">Figure 18: </span>Slip-Ring rotating at 60rpm</p>
+</div>
+</div>
+</div>
+
+<div id="outline-container-orgc5c1ef8" class="outline-3">
+<h3 id="orgc5c1ef8"><span class="section-number-3">4.2</span> Load data</h3>
+<div class="outline-text-3" id="text-4-2">
+<p>
+We load the data of the z axis of two geophones.
+</p>
+<div class="org-src-container">
+<pre class="src src-matlab">sr_off = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_008.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; sr_off = sr_off.data;
+sr_on  = load<span class="org-rainbow-delimiters-depth-1">(</span>'mat<span class="org-type">/</span>data_009.mat', <span class="org-string">'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; sr_on  = sr_on.data;
+sr_6r  = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_010.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; sr_6r  = sr_6r.data;
+sr_60r = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_011.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; sr_60r = sr_60r.data;
+</pre>
+</div>
+</div>
+</div>
+
+<div id="outline-container-org68d7016" class="outline-3">
+<h3 id="org68d7016"><span class="section-number-3">4.3</span> Time Domain</h3>
+<div class="outline-text-3" id="text-4-3">
+<p>
+We plot the time domain data for the direct measurement (figure <a href="#org47015a2">19</a>) and for the signal going through the slip-ring (figure <a href="#orgea3a17a">20</a>);
+</p>
+
+
+<div id="org47015a2" class="figure">
+<p><img src="figs/sr_direct_time.png" alt="sr_direct_time.png" />
+</p>
+<p><span class="figure-number">Figure 19: </span>Direct measurement</p>
+</div>
+
+
+
+<div id="orgea3a17a" class="figure">
+<p><img src="figs/sr_slipring_time.png" alt="sr_slipring_time.png" />
+</p>
+<p><span class="figure-number">Figure 20: </span>Measurement of the signal going through the Slip-Ring</p>
+</div>
+</div>
+</div>
+
+<div id="outline-container-org147ce89" class="outline-3">
+<h3 id="org147ce89"><span class="section-number-3">4.4</span> Frequency Domain</h3>
+<div class="outline-text-3" id="text-4-4">
+<p>
+We first compute some parameters that will be used for the PSD computation.
+</p>
+<div class="org-src-container">
+<pre class="src src-matlab">dt = sr_off<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">2</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-1">)</span><span class="org-type">-</span>sr_off<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">1</span>, <span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+
+Fs = <span class="org-highlight-numbers-number">1</span><span class="org-type">/</span>dt; <span class="org-comment">% [Hz]</span>
+
+win = hanning<span class="org-rainbow-delimiters-depth-1">(</span>ceil<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-highlight-numbers-number">10</span><span class="org-type">*</span>Fs<span class="org-rainbow-delimiters-depth-2">)</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+</pre>
+</div>
+
+<p>
+Then we compute the Power Spectral Density using <code>pwelch</code> function.
+</p>
+<div class="org-src-container">
+<pre class="src src-matlab"><span class="org-rainbow-delimiters-depth-1">[</span>pxdir, f<span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_off<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">1</span><span class="org-rainbow-delimiters-depth-2">)</span>, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
+<span class="org-rainbow-delimiters-depth-1">[</span>pxoff, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_off<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
+<span class="org-rainbow-delimiters-depth-1">[</span>pxon,  <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_on<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>,  win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
+<span class="org-rainbow-delimiters-depth-1">[</span>px6r,  <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_6r<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>,  win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
+<span class="org-rainbow-delimiters-depth-1">[</span>px60r, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>sr_60r<span class="org-rainbow-delimiters-depth-2">(</span><span class="org-type">:</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-2">)</span>, win, <span class="org-rainbow-delimiters-depth-2">[]</span>, <span class="org-rainbow-delimiters-depth-2">[]</span>, Fs<span class="org-rainbow-delimiters-depth-1">)</span>;
+</pre>
+</div>
+
+<p>
+And we plot the ASD of the measured signals (figure <a href="#orgf70ff7c">21</a>);
+</p>
+
+<div class="org-src-container">
+<pre class="src src-matlab"><span class="org-type">figure</span>;
+hold on;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxoff<span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'DisplayName', 'OFF'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxon<span class="org-rainbow-delimiters-depth-2">)</span>,  <span class="org-string">'DisplayName', 'ON'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>px6r<span class="org-rainbow-delimiters-depth-2">)</span>,  'DisplayName', '<span class="org-highlight-numbers-number">6rpm</span>'<span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>px60r<span class="org-rainbow-delimiters-depth-2">)</span>, 'DisplayName', '<span class="org-highlight-numbers-number">60rpm</span>'<span class="org-rainbow-delimiters-depth-1">)</span>;
+plot<span class="org-rainbow-delimiters-depth-1">(</span>f, sqrt<span class="org-rainbow-delimiters-depth-2">(</span>pxdir<span class="org-rainbow-delimiters-depth-2">)</span>, <span class="org-string">'k-', 'DisplayName', 'Direct'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 hold off;
 <span class="org-type">set</span><span class="org-rainbow-delimiters-depth-1">(</span><span class="org-variable-name">gca</span>, <span class="org-string">'xscale', 'log'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
 <span class="org-type">set</span><span class="org-rainbow-delimiters-depth-1">(</span><span class="org-variable-name">gca</span>, <span class="org-string">'yscale', 'log'</span><span class="org-rainbow-delimiters-depth-1">)</span>;
@@ -1315,21 +1525,31 @@ xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbo
 </div>
 
 
-<div id="org9493d78" class="figure">
-<p><img src="figs/comp_with_without_lpf.png" alt="comp_with_without_lpf.png" />
+<div id="orgf70ff7c" class="figure">
+<p><img src="figs/sr_psd_compare.png" alt="sr_psd_compare.png" />
 </p>
-<p><span class="figure-number">Figure 22: </span>Comparison of the measured signals with and without LPF</p>
+<p><span class="figure-number">Figure 21: </span>Comparison of the ASD of the measured signals when the slip-ring is ON, OFF and turning</p>
+</div>
+
+<div class="note">
+<p>
+<b>Questions:</b>
+</p>
+<ul class="org-ul">
+<li>Why is there some sharp peaks? Can this be due to aliasing?</li>
+<li>It is possible that the amplifiers were saturating during the measurements. This saturation could be due to high frequency noise.</li>
+</ul>
+
 </div>
 </div>
 </div>
 
-<div id="outline-container-org44b238b" class="outline-4">
-<h4 id="org44b238b"><span class="section-number-4">4.3.6</span> Conclusion</h4>
-<div class="outline-text-4" id="text-4-3-6">
+<div id="outline-container-org7392479" class="outline-3">
+<h3 id="org7392479"><span class="section-number-3">4.5</span> Conclusion</h3>
+<div class="outline-text-3" id="text-4-5">
 <div class="important">
 <ul class="org-ul">
-<li>Using the LPF, we don't have any perturbation coming from the slip-ring when it is on.</li>
-<li>However, we should use a smaller value of the capacitor to have a cut-off frequency at \(1kHz\).</li>
+<li>The measurements are re-done using an additional low pass filter at the input of the voltage amplifier</li>
 </ul>
 
 </div>
@@ -1337,10 +1557,9 @@ xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbo
 </div>
 </div>
 </div>
-</div>
 <div id="postamble" class="status">
-<p class="author">Author: Thomas Dehaeze</p>
-<p class="date">Created: 2019-05-10 ven. 10:06</p>
+<p class="author">Author: Dehaeze Thomas</p>
+<p class="date">Created: 2019-05-13 lun. 15:05</p>
 <p class="validation"><a href="http://validator.w3.org/check?uri=referer">Validate</a></p>
 </div>
 </body>
diff --git a/slip-ring-electrical-noise/index.org b/slip-ring-electrical-noise/index.org
index c30eac4..bc5c7cb 100644
--- a/slip-ring-electrical-noise/index.org
+++ b/slip-ring-electrical-noise/index.org
@@ -1,7 +1,55 @@
 #+TITLE: Measurements On the Slip-Ring
-#+SETUPFILE: ../config.org
+:DRAWER:
+#+STARTUP: overview
 
-* Effect of the Slip-Ring on the signal
+#+LANGUAGE: en
+#+EMAIL: dehaeze.thomas@gmail.com
+#+AUTHOR: Dehaeze Thomas
+
+#+HTML_LINK_HOME: ../index.html
+#+HTML_LINK_UP: ../index.html
+
+#+HTML_HEAD: <link rel="stylesheet" type="text/css" href="../css/htmlize.css"/>
+#+HTML_HEAD: <link rel="stylesheet" type="text/css" href="../css/readtheorg.css"/>
+#+HTML_HEAD: <link rel="stylesheet" type="text/css" href="../css/zenburn.css"/>
+#+HTML_HEAD: <script type="text/javascript" src="../js/jquery.min.js"></script>
+#+HTML_HEAD: <script type="text/javascript" src="../js/bootstrap.min.js"></script>
+#+HTML_HEAD: <script type="text/javascript" src="../js/jquery.stickytableheaders.min.js"></script>
+#+HTML_HEAD: <script type="text/javascript" src="../js/readtheorg.js"></script>
+
+#+HTML_MATHJAX: align: center tagside: right font: TeX
+
+#+PROPERTY: header-args:matlab  :session *MATLAB*
+#+PROPERTY: header-args:matlab+ :comments org
+#+PROPERTY: header-args:matlab+ :results none
+#+PROPERTY: header-args:matlab+ :exports both
+#+PROPERTY: header-args:matlab+ :eval no-export
+#+PROPERTY: header-args:matlab+ :output-dir figs
+
+#+PROPERTY: header-args:shell  :eval no-export
+:END:
+
+First, the noise induced by the slip-ring is measured when using geophones:
+- Section [[sec:meas_slip_ring_geophone]]:
+  - A geophone located at the sample location is measured with its signal going directly to the ADC and going through the slip-ring
+  - The voltage amplifiers where saturating due to high frequency noise
+- Section [[sec:meas_sr_geophone]]:
+  - A Low Pass Filter is added before the voltage amplifiers
+  - Using a Oscilloscope, high frequency noise at 40kHz generated by the slip-ring has been identified
+  - With the additional low pass filter at the input of the voltage amplifiers, the slip-ring don't add any measurable noise to the signal
+
+Then, we determine is the slip-ring add some noise to the signal when it is turning:
+- Section [[sec:meas_effect_sr]]:
+  - Noise is generated by the Speedgoat DAC and goes trough the slip-ring two times
+  - We measure the signal when it is OFF, ON but not turning and ON and turning
+  - However, the measurement is limited by the ADC noise
+- Section [[sec:meas_slip_ring]]:
+  - Voltage amplifiers are added, and the same measurements are done
+  - However, the voltage amplifiers are saturating because of high frequency noise
+- Section [[sec:meas_slip_ring_lpf]]:
+  - Low pass filter are added at the input of the voltage amplifier and the same measurement is done
+
+* Effect of the Slip-Ring on the signal when turned ON - Geophone measurement
   :PROPERTIES:
   :header-args:matlab+: :tangle matlab/meas_slip_ring_geophone.m
   :header-args:matlab+: :comments org :mkdirp yes
@@ -24,20 +72,32 @@
 #+end_note
 
 ** Experimental Setup
+*Goal*:
+The goal is to determine if some noise is added to a signal passing through the slip-ring.
+
+
+*Setup*:
 Two measurements are made with the control systems of all the stages turned OFF.
 
 One geophone is located on the marble while the other is located at the sample location (figure [[fig:setup_slipring]]).
 
+The two signals from the geophones are amplified with voltage amplifiers with the following settings:
+- Gain: 60dB
+- AC/DC switch: AC
+- Low pass filter at the output set at 1kHz
+
 #+name: fig:setup_slipring
 #+caption: Experimental Setup
 #+attr_html: :width 500px
 [[file:./img/IMG_20190430_112615.jpg]]
 
-The two measurements are:
-| Measurement File | Description                                                      |
-|------------------+------------------------------------------------------------------|
-| =meas_018.mat=   | Signal from the top geophone does not goes through the Slip-ring |
-| =meas_019.mat=   | Signal goes through the Slip-ring (as shown on the figure above) |
+
+*Measurements*:
+Two measurements are done:
+| Measurement File   | Description                                                      |
+|--------------------+------------------------------------------------------------------|
+| =mat/meas_018.mat= | Signal goes through the Slip-ring (as shown on the figure above) |
+| =mat/meas_019.mat= | Signal from the top geophone does not goes through the Slip-ring |
 
 Each of the measurement =mat= file contains one =data= array with 3 columns:
 | Column number | Description       |
@@ -59,19 +119,18 @@ Each of the measurement =mat= file contains one =data= array with 3 columns:
 We load the data of the z axis of two geophones.
 
 #+begin_src matlab :results none
-  d8 = load('mat/data_018.mat', 'data'); d8 = d8.data;
-  d9 = load('mat/data_019.mat', 'data'); d9 = d9.data;
+  meas_sr = load('mat/data_018.mat', 'data'); meas_sr = meas_sr.data;
+  meas_di = load('mat/data_019.mat', 'data'); meas_di = meas_di.data;
 #+end_src
 
 ** Analysis - Time Domain
 First, we compare the time domain signals for the two experiments (figure [[fig:slipring_time]]).
 
-
 #+begin_src matlab :results none
   figure;
   hold on;
-  plot(d9(:, 3), d9(:, 2), 'DisplayName', 'Slip-Ring');
-  plot(d8(:, 3), d8(:, 2), 'DisplayName', 'Wire');
+  plot(meas_di(:, 3), meas_di(:, 2), 'DisplayName', 'Geophone - Direct');
+  plot(meas_sr(:, 3), meas_sr(:, 2), 'DisplayName', 'Geophone - Slip-Ring');
   hold off;
   xlabel('Time [s]'); ylabel('Voltage [V]');
   xlim([0, 50]);
@@ -85,29 +144,30 @@ First, we compare the time domain signals for the two experiments (figure [[fig:
 #+end_src
 
 #+NAME: fig:slipring_time
-#+CAPTION: Effect of the Slip-Ring on the measured signal - Time domain
+#+CAPTION: Effect of the Slip-Ring on the measured signal of the geophone at the sample location - Time domain
 #+RESULTS: fig:slipring_time
 [[file:figs/slipring_time.png]]
 
 ** Analysis - Frequency Domain
 We then compute the Power Spectral Density of the two signals and we compare them (figure [[fig:slipring_asd]]).
+
 #+begin_src matlab :results none
-  dt = d8(2, 3) - d8(1, 3);
+  dt = meas_di(2, 3) - meas_di(1, 3);
   Fs = 1/dt;
 
-  win = hanning(ceil(1*Fs));
+  win = hanning(ceil(5*Fs));
 #+end_src
 
 #+begin_src matlab :results none
-  [pxx8, f] = pwelch(d8(:, 2), win, [], [], Fs);
-  [pxx9, ~] = pwelch(d9(:, 2), win, [], [], Fs);
+  [px_di, f] = pwelch(meas_di(:, 2), win, [], [], Fs);
+  [px_sr, ~] = pwelch(meas_sr(:, 2), win, [], [], Fs);
 #+end_src
 
 #+begin_src matlab :results none
   figure;
   hold on;
-  plot(f, sqrt(pxx9), 'DisplayName', 'Slip-Ring');
-  plot(f, sqrt(pxx8), 'DisplayName', 'Wire');
+  plot(f, sqrt(px_sr), 'DisplayName', 'Slip-Ring');
+  plot(f, sqrt(px_di), 'DisplayName', 'Wire');
   hold off;
   set(gca, 'xscale', 'log');
   set(gca, 'yscale', 'log');
@@ -123,23 +183,397 @@ We then compute the Power Spectral Density of the two signals and we compare the
 #+end_src
 
 #+NAME: fig:slipring_asd
-#+CAPTION: Effect of the Slip-Ring on the measured signal - Frequency domain
+#+CAPTION: Effect of the Slip-Ring on the measured signal of the geophone at the sample location - Frequency domain
 #+RESULTS: fig:slipring_asd
 [[file:figs/slipring_asd.png]]
 
 ** Conclusion
 #+begin_important
-- Connecting the geophone through the Slip-Ring seems to induce a lot of noise.
+  - The voltage amplifiers are saturating during the measurements (as shown by the LED on figure [[fig:setup_slipring]])
+  - This saturation is mainly due to high frequency noise => a LPF will be added at the input of the voltage amplifiers in the further measurements
+  - The measurements will be redone
 #+end_important
 
+* Measure of the noise induced by the Slip-Ring using voltage amplifiers - Geophone
+  :PROPERTIES:
+  :header-args:matlab+: :tangle matlab/meas_sr_geophone.m
+  :header-args:matlab+: :comments org :mkdirp yes
+  :END:
+  <<sec:meas_sr_geophone>>
+
+#+begin_src bash :exports none :results none
+  if [ matlab/meas_sr_geophone.m -nt data/meas_sr_geophone.zip ]; then
+    cp matlab/meas_sr_geophone.m meas_sr_geophone.m;
+    zip data/meas_sr_geophone \
+        mat/data_012.mat \
+        mat/data_013.mat \
+        mat/data_016.mat \
+        mat/data_017.mat \
+        meas_sr_geophone.m;
+    rm meas_sr_geophone.m;
+  fi
+#+end_src
+
 #+begin_note
-*Remaining questions to answer*:
-- Why is there a sharp peak at 300Hz?
-- Why the use of the Slip-Ring does induce a noise?
-- Can the capacitive/inductive properties of the wires in the Slip-ring does not play well with the geophone? (resonant RLC circuit)
+  All the files (data and Matlab scripts) are accessible [[file:data/meas_sr_geophone.zip][here]].
 #+end_note
 
-* Effect of the rotation of the Slip-Ring
+** Matlab Init                                              :noexport:ignore:
+#+begin_src matlab :tangle no :exports none :results silent :noweb yes :var current_dir=(file-name-directory buffer-file-name)
+  <<matlab-dir>>
+#+end_src
+
+#+begin_src matlab :exports none :results silent :noweb yes
+  <<matlab-init>>
+#+end_src
+
+** First Measurement without LPF
+*** Measurement Description
+*Goal*:
+- Determine if the noise induced by the slip-ring is a limiting factor when measuring the signal coming from a geophone
+
+*Setup*:
+- The geophone is located at the sample location
+- The two Voltage amplifiers have the same following settings:
+  - Gain: 60dB
+  - AC/DC option: AC
+  - Low pass filter at the output set to 1kHz
+- The signal from the geophone is split into two using a T-BNC:
+  - One part goes directly to the voltage amplifier and then to the ADC
+  - The other part goes to the slip-ring=>voltage amplifier=>ADC
+
+*Measurements*:
+Two measurements are done:
+| Measurement File | Description   |
+|------------------+---------------|
+| =data_012=       | Slip-Ring OFF |
+| =data_013=       | Slip-Ring ON  |
+
+Each of the measurement =mat= file contains one =data= array with 3 columns:
+| Column number | Description                                                                |
+|---------------+----------------------------------------------------------------------------|
+|             1 | Measure of the geophone at the sample position with a direct wire          |
+|             2 | Measure of the geophone at the sample position going through the slip-ring |
+|             3 | Time                                                                       |
+
+*** Load data
+We load the data of the z axis of two geophones.
+#+begin_src matlab :results none
+  sr_off = load('mat/data_012.mat', 'data'); sr_off = sr_off.data;
+  sr_on  = load('mat/data_013.mat', 'data'); sr_on  = sr_on.data;
+#+end_src
+
+*** Time Domain
+We compare the signal when the Slip-Ring is OFF (figure [[fig:sr_geophone_time_off]]) and when it is ON (figure [[fig:sr_geophone_time_on]]).
+
+#+begin_src matlab :results none :exports none
+  figure;
+  hold on;
+  plot(sr_off(:, 3), sr_off(:, 1), 'DisplayName', 'Direct');
+  plot(sr_off(:, 3), sr_off(:, 2), 'DisplayName', 'Slip-Ring');
+  hold off;
+  legend('Location', 'northeast');
+  xlabel('Time [s]');
+  ylabel('Voltage [V]');
+#+end_src
+
+#+NAME: fig:sr_geophone_time_off
+#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
+#+begin_src matlab :var filepath="figs/sr_geophone_time_off.pdf" :var figsize="wide-normal" :post pdf2svg(file=*this*, ext="png")
+  <<plt-matlab>>
+#+end_src
+
+#+NAME: fig:sr_geophone_time_off
+#+CAPTION: Comparison of the time domain signals when the slip-ring is OFF
+#+RESULTS: fig:sr_geophone_time_off
+[[file:figs/sr_geophone_time_off.png]]
+
+#+begin_src matlab :results none :exports none
+  figure;
+  hold on;
+  plot(sr_on(:, 3),  sr_on(:, 1),  'DisplayName', 'Direct');
+  plot(sr_on(:, 3),  sr_on(:, 2),  'DisplayName', 'Slip-Ring');
+  hold off;
+  legend('Location', 'northeast');
+  xlabel('Time [s]');
+  ylabel('Voltage [V]');
+#+end_src
+
+#+NAME: fig:sr_geophone_time_on
+#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
+#+begin_src matlab :var filepath="figs/sr_geophone_time_on.pdf" :var figsize="wide-normal" :post pdf2svg(file=*this*, ext="png")
+  <<plt-matlab>>
+#+end_src
+
+#+NAME: fig:sr_geophone_time_on
+#+CAPTION: Comparison of the time domain signals when the slip-ring is ON
+#+RESULTS: fig:sr_geophone_time_on
+[[file:figs/sr_geophone_time_on.png]]
+
+*** Frequency Domain
+We first compute some parameters that will be used for the PSD computation.
+#+begin_src matlab :results none
+  dt = sr_off(2, 3)-sr_off(1, 3);
+
+  Fs = 1/dt; % [Hz]
+
+  win = hanning(ceil(10*Fs));
+#+end_src
+
+Then we compute the Power Spectral Density using =pwelch= function.
+#+begin_src matlab :results none
+  % Direct measure
+  [pxdoff, ~] = pwelch(sr_off(:, 1), win, [], [], Fs);
+  [pxdon,  ~] = pwelch(sr_on(:, 1),  win, [], [], Fs);
+
+  % Slip-Ring measure
+  [pxsroff, f] = pwelch(sr_off(:, 2), win, [], [], Fs);
+  [pxsron,  ~] = pwelch(sr_on(:, 2),  win, [], [], Fs);
+#+end_src
+
+Finally, we compare the Amplitude Spectral Density of the signals (figure [[fig:sr_geophone_asd]]);
+
+#+begin_src matlab :results none
+  figure;
+  hold on;
+  plot(f, sqrt(pxdoff), 'DisplayName', 'Direct - OFF');
+  plot(f, sqrt(pxsroff), 'DisplayName', 'Slip-Ring - OFF');
+  plot(f, sqrt(pxdon),  'DisplayName', 'Direct - ON');
+  plot(f, sqrt(pxsron),  'DisplayName', 'Slip-Ring - ON');
+  hold off;
+  set(gca, 'xscale', 'log');
+  set(gca, 'yscale', 'log');
+  xlabel('Frequency [Hz]'); ylabel('ASD of the measured Voltage $\left[\frac{V}{\sqrt{Hz}}\right]$')
+  legend('Location', 'northeast');
+  xlim([0.1, 500]);
+#+end_src
+
+#+NAME: fig:sr_geophone_asd
+#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
+#+begin_src matlab :var filepath="figs/sr_geophone_asd.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
+  <<plt-matlab>>
+#+end_src
+
+#+NAME: fig:sr_geophone_asd
+#+CAPTION: Comparison of the Amplitude Spectral Sensity
+#+RESULTS: fig:sr_geophone_asd
+[[file:figs/sr_geophone_asd.png]]
+
+#+begin_src matlab :results none :exports none
+  xlim([100, 500]);
+#+end_src
+
+#+NAME: fig:sr_geophone_asd_zoom
+#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
+#+begin_src matlab :var filepath="figs/sr_geophone_asd_zoom.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
+  <<plt-matlab>>
+#+end_src
+
+#+NAME: fig:sr_geophone_asd_zoom
+#+CAPTION: Comparison of the Amplitude Spectral Sensity - Zoom
+#+RESULTS: fig:sr_geophone_asd_zoom
+[[file:figs/sr_geophone_asd_zoom.png]]
+
+*** Conclusion
+#+begin_important
+  - The fact that the Slip-Ring is turned ON adds some noise to the signals
+  - The signal going through the Slip-Ring is less noisy than the one going directly to the ADC
+  - This could be due to better electromagnetic isolation in the slip-ring
+
+  *Questions*:
+  - Can the sharp peak on figure [[fig:sr_geophone_asd_zoom]] be due to the Aliasing?
+#+end_important
+
+** Measurement using an oscilloscope
+*** Measurement Setup
+We are now measuring the same signals than in the previous section, but with an oscilloscope instead of with the Speedgoat ADC.
+
+*** Observations
+Then the Slip-Ring is ON (figure [[fig:oscilloscope_sr_on]]), we observe a signal at 40kHz with a peak-to-peak amplitude of 200mV for the direct measure and 100mV for the signal going through the Slip-Ring.
+
+Then the Slip-Ring is OFF, we don't observe this noise at 40kHz anymore (figure [[fig:oscilloscope_sr_off]]).
+
+#+name: fig:oscilloscope_sr_on
+#+caption: Signals measured by the oscilloscope - Slip-Ring ON - Yellow: Direct measure - Blue: Through Slip-Ring
+#+attr_html: :width 500px
+[[file:./img/IMG_20190506_160420.jpg]]
+
+#+name: fig:oscilloscope_sr_off
+#+caption: Signals measured by the oscilloscope - Slip-Ring OFF - Yellow: Direct measure - Blue: Through Slip-Ring
+#+attr_html: :width 500px
+[[file:./img/IMG_20190506_160438.jpg]]
+
+*** Conclusion
+#+begin_important
+  - By looking at the signals using an oscilloscope, there is a lot of high frequency noise when turning on the Slip-Ring
+  - This can eventually saturate the voltage amplifiers (seen by a led indicating saturation)
+  - The choice is to *add a Low pass filter before the voltage amplifiers* to not saturate them and filter the noise.
+#+end_important
+
+** New measurements with a LPF before the Voltage Amplifiers
+*** Setup description
+*Goal*:
+The goal is to see if we can remove high frequency noise from the signals before the voltage amplifiers in order to not saturate them.
+
+*Setup*:
+We are measuring the signal from a geophone put at the sample position.
+Using a BNC slitter, one part is going directly to the Low pass filter, voltage amplifier and ADC (first column), the other part is going through the slip ring before the low pass filter and the voltage amplifier (second column).
+
+The two voltage amplifiers have the same following settings:
+  - Gain: 60dB
+  - AC/DC option: DC
+  - Low pass filter at the output set to 1kHz
+
+The low pass filter is a first order low pass filter RC circuit. It is added before the Voltage Amplifiers and has the following values:
+\begin{aligned}
+  R &= 1k\Omega \\
+  C &= 1\mu F
+\end{aligned}
+
+And the cut-off frequency is $f_c = \frac{1}{RC} = 160Hz$.
+
+*Measurements*:
+Two measurements are done:
+| Measurement File   | Description                                                     |
+|--------------------+-----------------------------------------------------------------|
+| =mat/data_016.mat= | Signal from the geophone at the sample location - Slip-Ring OFF |
+| =mat/data_017.mat= | Signal from the geophone at the sample location - Slip-Ring ON  |
+
+Each of the measurement =mat= file contains one =data= array with 3 columns:
+| Column number | Description                        |
+|---------------+------------------------------------|
+|             1 | Direct measurement                 |
+|             2 | Signal going through the slip-ring |
+|             3 | Time                               |
+
+*** Load data
+We load the data of the z axis of two geophones.
+#+begin_src matlab :results none
+  sr_lpf_off = load('mat/data_016.mat', 'data'); sr_lpf_off = sr_lpf_off.data;
+  sr_lpf_on  = load('mat/data_017.mat', 'data'); sr_lpf_on  = sr_lpf_on.data;
+#+end_src
+
+*** Time Domain
+We compare the signal when the Slip-Ring is OFF (figure [[fig:sr_lpf_geophone_time_off]]) and when it is ON (figure [[fig:sr_lpf_geophone_time_on]]).
+
+#+begin_src matlab :results none :exports none
+  figure;
+  hold on;
+  plot(sr_lpf_off(:, 3), sr_lpf_off(:, 1)-mean(sr_lpf_off(:, 1)), 'DisplayName', 'Direct');
+  plot(sr_lpf_off(:, 3), sr_lpf_off(:, 2)-mean(sr_lpf_off(:, 2)), 'DisplayName', 'Slip-Ring');
+  hold off;
+  xlim([0, 100]); ylim([-1, 1]);
+  legend('Location', 'northeast');
+  xlabel('Time [s]');
+  ylabel('Voltage [V]');
+#+end_src
+
+#+NAME: fig:sr_lpf_geophone_time_off
+#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
+#+begin_src matlab :var filepath="figs/sr_lpf_geophone_time_off.pdf" :var figsize="wide-normal" :post pdf2svg(file=*this*, ext="png")
+  <<plt-matlab>>
+#+end_src
+
+#+NAME: fig:sr_lpf_geophone_time_off
+#+CAPTION: Comparison of the time domain signals when the slip-ring is OFF
+#+RESULTS: fig:sr_lpf_geophone_time_off
+[[file:figs/sr_lpf_geophone_time_off.png]]
+
+#+begin_src matlab :results none :exports none
+  figure;
+  hold on;
+  plot(sr_lpf_on(:, 3),  sr_lpf_on(:, 1)-mean(sr_lpf_on(:, 1)),  'DisplayName', 'Direct');
+  plot(sr_lpf_on(:, 3),  sr_lpf_on(:, 2)-mean(sr_lpf_on(:, 2)),  'DisplayName', 'Slip-Ring');
+  hold off;
+  xlim([0, 100]); ylim([-1, 1]);
+  legend('Location', 'northeast');
+  xlabel('Time [s]');
+  ylabel('Voltage [V]');
+#+end_src
+
+#+NAME: fig:sr_lpf_geophone_time_on
+#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
+#+begin_src matlab :var filepath="figs/sr_lpf_geophone_time_on.pdf" :var figsize="wide-normal" :post pdf2svg(file=*this*, ext="png")
+  <<plt-matlab>>
+#+end_src
+
+#+NAME: fig:sr_lpf_geophone_time_on
+#+CAPTION: Comparison of the time domain signals when the slip-ring is ON
+#+RESULTS: fig:sr_lpf_geophone_time_on
+[[file:figs/sr_lpf_geophone_time_on.png]]
+
+*** Frequency Domain
+We first compute some parameters that will be used for the PSD computation.
+#+begin_src matlab :results none
+  dt = sr_lpf_off(2, 3)-sr_lpf_off(1, 3);
+
+  Fs = 1/dt; % [Hz]
+
+  win = hanning(ceil(10*Fs));
+#+end_src
+
+Then we compute the Power Spectral Density using =pwelch= function.
+#+begin_src matlab :results none
+  % Direct measure
+  [pxd_lpf_off, ~] = pwelch(sr_lpf_off(:, 1), win, [], [], Fs);
+  [pxd_lpf_on,  ~] = pwelch(sr_lpf_on(:, 1),  win, [], [], Fs);
+
+  % Slip-Ring measure
+  [pxsr_lpf_off, f] = pwelch(sr_lpf_off(:, 2), win, [], [], Fs);
+  [pxsr_lpf_on,  ~] = pwelch(sr_lpf_on(:, 2),  win, [], [], Fs);
+#+end_src
+
+Finally, we compare the Amplitude Spectral Density of the signals (figure [[fig:sr_lpf_geophone_asd]]);
+
+#+begin_src matlab :results none
+  figure;
+  hold on;
+  plot(f, sqrt(pxd_lpf_off),  'DisplayName', 'Direct - OFF');
+  plot(f, sqrt(pxsr_lpf_off), 'DisplayName', 'Slip-Ring - OFF');
+  plot(f, sqrt(pxd_lpf_on),   'DisplayName', 'Direct - ON');
+  plot(f, sqrt(pxsr_lpf_on),  'DisplayName', 'Slip-Ring - ON');
+  hold off;
+  xlim([0.1, 500]);
+  set(gca, 'xscale', 'log'); set(gca, 'yscale', 'log');
+  xlabel('Frequency [Hz]'); ylabel('ASD of the measured Voltage $\left[\frac{V}{\sqrt{Hz}}\right]$')
+  legend('Location', 'soutwest');
+#+end_src
+
+#+NAME: fig:sr_lpf_geophone_asd
+#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
+#+begin_src matlab :var filepath="figs/sr_lpf_geophone_asd.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
+  <<plt-matlab>>
+#+end_src
+
+#+NAME: fig:sr_lpf_geophone_asd
+#+CAPTION: Comparison of the Amplitude Spectral Sensity
+#+RESULTS: fig:sr_lpf_geophone_asd
+[[file:figs/sr_lpf_geophone_asd.png]]
+
+#+begin_src matlab :results none :exports none
+  xlim([100, 500]);
+#+end_src
+
+#+NAME: fig:sr_lpf_geophone_asd_zoom
+#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
+#+begin_src matlab :var filepath="figs/sr_lpf_geophone_asd_zoom.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
+  <<plt-matlab>>
+#+end_src
+
+#+NAME: fig:sr_lpf_geophone_asd_zoom
+#+CAPTION: Comparison of the Amplitude Spectral Sensity - Zoom
+#+RESULTS: fig:sr_lpf_geophone_asd_zoom
+[[file:figs/sr_lpf_geophone_asd_zoom.png]]
+
+*** Conclusion
+#+begin_important
+  - Using the LPF, we don't see any additional noise coming from the slip-ring when it is turned ON
+  - However, we should use a smaller value of the capacitor to have a cut-off frequency at $1kHz$
+  - We here observe a signal at $50Hz$ and its harmonics
+#+end_important
+
+* TODO New LPF at 1kHz
+* Effect of the rotation of the Slip-Ring - Noise
   :PROPERTIES:
   :header-args:matlab+: :tangle matlab/meas_effect_sr.m
   :header-args:matlab+: :comments org :mkdirp yes
@@ -162,28 +596,32 @@ We then compute the Power Spectral Density of the two signals and we compare the
 #+end_note
 
 ** Measurement Description
-Random Signal is generated by one DAC of the SpeedGoat.
+*Goal*:
+The goal is to determine if the signal is altered when the spindle is rotating.
+
+
+*Setup*:
+Random Signal is generated by one SpeedGoat DAC.
 
 The signal going out of the DAC is split into two:
 - one BNC cable is directly connected to one ADC of the SpeedGoat
 - one BNC cable goes two times in the Slip-Ring (from bottom to top and then from top to bottom) and then is connected to one ADC of the SpeedGoat
 
-Two measurements are done.
-| Data File          | Description           |
-|--------------------+-----------------------|
-| =mat/data_001.mat= | Slip-ring not turning |
-| =mat/data_002.mat= | Slip-ring turning     |
+All the stages are turned OFF except the Slip-Ring.
+
+
+*Measurements*:
+| Data File          | Description                  |
+|--------------------+------------------------------|
+| =mat/data_001.mat= | Slip-ring not turning but ON |
+| =mat/data_002.mat= | Slip-ring turning at 1rpm    |
 
 For each measurement, the measured signals are:
-| Data File | Description                        |
-|-----------+------------------------------------|
-| =t=       | Time vector                        |
-| =x1=      | Direct signal                      |
-| =x2=      | Signal going through the Slip-Ring |
-
-The goal is to determine is the signal is altered when the spindle is rotating.
-
-Here, the rotation speed of the Slip-Ring is set to 1rpm.
+| Variable | Description                        |
+|----------+------------------------------------|
+| =t=      | Time vector                        |
+| =x1=     | Direct signal                      |
+| =x2=     | Signal going through the Slip-Ring |
 
 ** Matlab Init                                              :noexport:ignore:
 #+begin_src matlab :tangle no :exports none :results silent :noweb yes :var current_dir=(file-name-directory buffer-file-name)
@@ -285,12 +723,11 @@ We now look at the difference between the signal directly measured by the ADC an
 
 ** Conclusion
 #+begin_note
-  *Remaining questions*:
-  - Should the measurement be redone using voltage amplifiers?
-  - Use higher rotation speed and measure for longer periods (to have multiple revolutions) ?
+  - The measurement is mostly limited by the resolution of the Speedgoat DAC (16bits over $\pm 10 V$)
+  - In section [[sec:meas_slip_ring]], the same measurement is done but voltage amplifiers are added to amplify the noise
 #+end_note
 
-* Measure of the noise induced by the Slip-Ring
+* Measure of the noise induced by the Slip-Ring using voltage amplifiers - Noise
   :PROPERTIES:
   :header-args:matlab+: :tangle matlab/meas_slip_ring.m
   :header-args:matlab+: :comments org :mkdirp yes
@@ -316,13 +753,17 @@ We now look at the difference between the signal directly measured by the ADC an
 
 ** Measurement Description
 *Goal*:
-- Determine the noise induced by the slip-ring
+- Determine the noise induced by the slip-ring when turned ON and when rotating
+
 
 *Setup*:
-- 0V is generated by the DAC of the Speedgoat
-- Using a T, one part goes directly to the ADC
-- The other part goes to the slip-ring 2 times and then to the ADC
-- The parameters of the Voltage Amplifier are: 80dB, AC, 1kHz
+- 0V is generated by one Speedgoat DAC
+- Using a T, one part goes directly to one Speedgoat ADC
+- The other part goes to the slip-ring 2 times and then to one voltage amplifier before going to the ADC
+- The parameters of the Voltage Amplifier are:
+  - gain of 80dB
+  - AC/DC option to AC (it adds an high pass filter at 1.5Hz at the input of the voltage amplifier)
+  - Output Low pass filter set at 1kHz
 - Every stage of the station is OFF
 
 First column: Direct measure
@@ -330,10 +771,19 @@ Second column: Slip-ring measure
 
 
 *Measurements*:
-- =data_008=: Slip-Ring OFF
-- =data_009=: Slip-Ring ON
-- =data_010=: Slip-Ring ON and omega=6rpm
-- =data_011=: Slip-Ring ON and omega=60rpm
+| Data File          | Description                  |
+|--------------------+------------------------------|
+| =mat/data_008.mat= | Slip-Ring OFF                |
+| =mat/data_009.mat= | Slip-Ring ON                 |
+| =mat/data_010.mat= | Slip-Ring ON and omega=6rpm  |
+| =mat/data_011.mat= | Slip-Ring ON and omega=60rpm |
+
+Each of the measurement =mat= file contains one =data= array with 3 columns:
+| Column number | Description                        |
+|---------------+------------------------------------|
+|             1 | Signal going directly to the ADC   |
+|             2 | Signal going through the Slip-Ring |
+|             3 | Time                               |
 
 #+name: fig:setup_sr_6rpm
 #+caption: Slip-Ring rotating at 6rpm
@@ -459,383 +909,33 @@ And we plot the ASD of the measured signals (figure [[fig:sr_psd_compare]]);
 #+RESULTS: fig:sr_psd_compare
 [[file:figs/sr_psd_compare.png]]
 
-** Conclusion
-#+begin_important
+#+begin_note
   *Questions:*
   - Why is there some sharp peaks? Can this be due to aliasing?
-  - It is possible that the amplifiers were saturating during the measurements => should redo the measurements with a low pass filter before the voltage amplifier
-#+end_important
+  - It is possible that the amplifiers were saturating during the measurements. This saturation could be due to high frequency noise.
+#+end_note
 
-* Measure of the noise induced by the slip ring when using a geophone
+** Conclusion
+#+begin_important
+  - The measurements are re-done using an additional low pass filter at the input of the voltage amplifier
+#+end_important
+* TODO Measure of the noise induced by the Slip-Ring rotation - LPF added
   :PROPERTIES:
-  :header-args:matlab+: :tangle matlab/meas_sr_geophone.m
+  :header-args:matlab+: :tangle matlab/meas_slip_ring_lpf.m
   :header-args:matlab+: :comments org :mkdirp yes
   :END:
-  <<sec:meas_sr_geophone>>
+  <<sec:meas_slip_ring_lpf>>
 
 #+begin_src bash :exports none :results none
-  if [ matlab/meas_sr_geophone.m -nt data/meas_sr_geophone.zip ]; then
-    cp matlab/meas_sr_geophone.m meas_sr_geophone.m;
-    zip data/meas_sr_geophone \
-        mat/data_012.mat \
-        mat/data_013.mat \
-        mat/data_016.mat \
-        mat/data_017.mat \
-        meas_sr_geophone.m;
-    rm meas_sr_geophone.m;
+  if [ matlab/meas_slip_ring_lpf.m -nt data/meas_slip_ring_lpf.zip ]; then
+    cp matlab/meas_slip_ring_lpf.m meas_slip_ring_lpf.m;
+    zip data/meas_slip_ring_lpf \
+        mat/data.mat \
+        meas_slip_ring_lpf.m
+    rm meas_slip_ring_lpf.m;
   fi
 #+end_src
 
 #+begin_note
-  All the files (data and Matlab scripts) are accessible [[file:data/meas_sr_geophone.zip][here]].
+  All the files (data and Matlab scripts) are accessible [[file:data/meas_slip_ring_lpf.zip][here]].
 #+end_note
-
-** Matlab Init                                              :noexport:ignore:
-#+begin_src matlab :tangle no :exports none :results silent :noweb yes :var current_dir=(file-name-directory buffer-file-name)
-  <<matlab-dir>>
-#+end_src
-
-#+begin_src matlab :exports none :results silent :noweb yes
-  <<matlab-init>>
-#+end_src
-
-** First Measurement without LPF
-*** Measurement Description
-*Goal*:
-- Determine if the noise induced by the slip-ring is a limiting factor when measuring the signal coming from a geophone
-
-*Setup*:
-- The geophone is located at the sample location
-- The two Voltage amplifiers have the same following settings:
-  - AC
-  - 60dB
-  - 1kHz
-- The signal from the geophone is split into two using a T-BNC:
-  - One part goes directly to the voltage amplifier and then to the ADC.
-  - The other part goes to the slip-ring=>voltage amplifier=>ADC.
-
-First column: Direct measure
-Second column: Slip-ring measure
-
-*Measurements*:
-- =data_012=: Slip-Ring OFF
-- =data_013=: Slip-Ring ON
-
-*** Load data
-We load the data of the z axis of two geophones.
-#+begin_src matlab :results none
-  sr_off = load('mat/data_012.mat', 'data'); sr_off = sr_off.data;
-  sr_on  = load('mat/data_013.mat', 'data'); sr_on  = sr_on.data;
-#+end_src
-
-*** Time Domain
-We compare the signal when the Slip-Ring is OFF (figure [[fig:sr_geophone_time_off]]) and when it is ON (figure [[fig:sr_geophone_time_on]]).
-
-#+begin_src matlab :results none :exports none
-  figure;
-  hold on;
-  plot(sr_off(:, 3), sr_off(:, 1), 'DisplayName', 'Direct');
-  plot(sr_off(:, 3), sr_off(:, 2), 'DisplayName', 'Slip-Ring');
-  hold off;
-  legend('Location', 'northeast');
-  xlabel('Time [s]');
-  ylabel('Voltage [V]');
-#+end_src
-
-#+NAME: fig:sr_geophone_time_off
-#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
-#+begin_src matlab :var filepath="figs/sr_geophone_time_off.pdf" :var figsize="wide-normal" :post pdf2svg(file=*this*, ext="png")
-  <<plt-matlab>>
-#+end_src
-
-#+NAME: fig:sr_geophone_time_off
-#+CAPTION: Comparison of the time domain signals when the slip-ring is OFF
-#+RESULTS: fig:sr_geophone_time_off
-[[file:figs/sr_geophone_time_off.png]]
-
-#+begin_src matlab :results none :exports none
-  figure;
-  hold on;
-  plot(sr_on(:, 3),  sr_on(:, 1),  'DisplayName', 'Direct');
-  plot(sr_on(:, 3),  sr_on(:, 2),  'DisplayName', 'Slip-Ring');
-  hold off;
-  legend('Location', 'northeast');
-  xlabel('Time [s]');
-  ylabel('Voltage [V]');
-#+end_src
-
-#+NAME: fig:sr_geophone_time_on
-#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
-#+begin_src matlab :var filepath="figs/sr_geophone_time_on.pdf" :var figsize="wide-normal" :post pdf2svg(file=*this*, ext="png")
-  <<plt-matlab>>
-#+end_src
-
-#+NAME: fig:sr_geophone_time_on
-#+CAPTION: Comparison of the time domain signals when the slip-ring is ON
-#+RESULTS: fig:sr_geophone_time_on
-[[file:figs/sr_geophone_time_on.png]]
-
-*** Frequency Domain
-We first compute some parameters that will be used for the PSD computation.
-#+begin_src matlab :results none
-  dt = sr_off(2, 3)-sr_off(1, 3);
-
-  Fs = 1/dt; % [Hz]
-
-  win = hanning(ceil(10*Fs));
-#+end_src
-
-Then we compute the Power Spectral Density using =pwelch= function.
-#+begin_src matlab :results none
-  % Direct measure
-  [pxdoff, ~] = pwelch(sr_off(:, 1), win, [], [], Fs);
-  [pxdon,  ~] = pwelch(sr_on(:, 1),  win, [], [], Fs);
-
-  % Slip-Ring measure
-  [pxsroff, f] = pwelch(sr_off(:, 2), win, [], [], Fs);
-  [pxsron,  ~] = pwelch(sr_on(:, 2),  win, [], [], Fs);
-#+end_src
-
-Finally, we compare the Amplitude Spectral Density of the signals (figure [[fig:sr_geophone_asd]]);
-
-#+begin_src matlab :results none
-  figure;
-  hold on;
-  plot(f, sqrt(pxdoff), 'DisplayName', 'Direct - OFF');
-  plot(f, sqrt(pxsroff), 'DisplayName', 'Slip-Ring - OFF');
-  plot(f, sqrt(pxdon),  'DisplayName', 'Direct - ON');
-  plot(f, sqrt(pxsron),  'DisplayName', 'Slip-Ring - ON');
-  hold off;
-  set(gca, 'xscale', 'log');
-  set(gca, 'yscale', 'log');
-  xlabel('Frequency [Hz]'); ylabel('ASD of the measured Voltage $\left[\frac{V}{\sqrt{Hz}}\right]$')
-  legend('Location', 'northeast');
-  xlim([0.1, 500]);
-#+end_src
-
-#+NAME: fig:sr_geophone_asd
-#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
-#+begin_src matlab :var filepath="figs/sr_geophone_asd.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
-  <<plt-matlab>>
-#+end_src
-
-#+NAME: fig:sr_geophone_asd
-#+CAPTION: Comparison of the Amplitude Spectral Sensity
-#+RESULTS: fig:sr_geophone_asd
-[[file:figs/sr_geophone_asd.png]]
-
-#+begin_src matlab :results none :exports none
-  xlim([100, 500]);
-#+end_src
-
-#+NAME: fig:sr_geophone_asd_zoom
-#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
-#+begin_src matlab :var filepath="figs/sr_geophone_asd_zoom.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
-  <<plt-matlab>>
-#+end_src
-
-#+NAME: fig:sr_geophone_asd_zoom
-#+CAPTION: Comparison of the Amplitude Spectral Sensity - Zoom
-#+RESULTS: fig:sr_geophone_asd_zoom
-[[file:figs/sr_geophone_asd_zoom.png]]
-
-*** Conclusion
-#+begin_important
-  - The fact that the Slip-Ring is turned ON adds some noise to the signal.
-  - The signal going through the Slip-Ring is less noisy than the one going directly to the ADC.
-  - This could be due to less good electromagnetic isolation.
-
-  *Questions*:
-  - Can the sharp peak on figure [[fig:sr_geophone_asd_zoom]] be due to the Aliasing?
-#+end_important
-
-** Measurement using an oscilloscope
-*** Measurement Setup
-Know we are measuring the same signals but using an oscilloscope instead of the Speedgoat ADC.
-
-*** Observations
-Then the Slip-Ring is ON (figure [[fig:oscilloscope_sr_on]]), we observe a signal at 40kHz with a peak-to-peak amplitude of 200mV for the direct measure and 100mV for the signal going through the Slip-Ring.
-
-Then the Slip-Ring is OFF, we don't observe this 40kHz anymore (figure [[fig:oscilloscope_sr_off]]).
-
-#+name: fig:oscilloscope_sr_on
-#+caption: Signals measured by the oscilloscope - Slip-Ring ON - Yellow: Direct measure - Blue: Through Slip-Ring
-#+attr_html: :width 500px
-[[file:./img/IMG_20190506_160420.jpg]]
-
-#+name: fig:oscilloscope_sr_off
-#+caption: Signals measured by the oscilloscope - Slip-Ring OFF - Yellow: Direct measure - Blue: Through Slip-Ring
-#+attr_html: :width 500px
-[[file:./img/IMG_20190506_160438.jpg]]
-
-*** Conclusion
-#+begin_important
-  - By looking at the signals using an oscilloscope, there is a lot of high frequency noise when turning on the Slip-Ring
-  - This can eventually saturate the voltage amplifiers (seen by a led indicating saturation)
-  - The choice is to *add a Low pass filter before the voltage amplifiers* to not saturate them and filter the noise.
-#+end_important
-
-** New measurements with a LPF before the Voltage Amplifiers
-*** Setup description
-A first order low pass filter is added before the Voltage Amplifiers with the following values:
-\begin{aligned}
-  R &= 1k\Omega \\
-  C &= 1\mu F
-\end{aligned}
-
-And we have a cut-off frequency of $f_c = \frac{1}{RC} = 160Hz$.
-
-We are measuring the signal from a geophone put on the marble with and without the added LPF:
-- with the slip ring OFF: =mat/data_016.mat=
-- with the slip ring ON: =mat/data_017.mat=
-
-*** Load data
-We load the data of the z axis of two geophones.
-#+begin_src matlab :results none
-  sr_lpf_off = load('mat/data_016.mat', 'data'); sr_lpf_off = sr_lpf_off.data;
-  sr_lpf_on  = load('mat/data_017.mat', 'data'); sr_lpf_on  = sr_lpf_on.data;
-#+end_src
-
-*** Time Domain
-We compare the signal when the Slip-Ring is OFF (figure [[fig:sr_lpf_geophone_time_off]]) and when it is ON (figure [[fig:sr_lpf_geophone_time_on]]).
-
-#+begin_src matlab :results none :exports none
-  figure;
-  hold on;
-  plot(sr_lpf_off(:, 3), sr_lpf_off(:, 1), 'DisplayName', 'Direct');
-  plot(sr_lpf_off(:, 3), sr_lpf_off(:, 2), 'DisplayName', 'Slip-Ring');
-  hold off;
-  legend('Location', 'northeast');
-  xlabel('Time [s]');
-  ylabel('Voltage [V]');
-#+end_src
-
-#+NAME: fig:sr_lpf_geophone_time_off
-#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
-#+begin_src matlab :var filepath="figs/sr_lpf_geophone_time_off.pdf" :var figsize="wide-normal" :post pdf2svg(file=*this*, ext="png")
-  <<plt-matlab>>
-#+end_src
-
-#+NAME: fig:sr_lpf_geophone_time_off
-#+CAPTION: Comparison of the time domain signals when the slip-ring is OFF
-#+RESULTS: fig:sr_lpf_geophone_time_off
-[[file:figs/sr_lpf_geophone_time_off.png]]
-
-#+begin_src matlab :results none :exports none
-  figure;
-  hold on;
-  plot(sr_lpf_on(:, 3),  sr_lpf_on(:, 1),  'DisplayName', 'Direct');
-  plot(sr_lpf_on(:, 3),  sr_lpf_on(:, 2),  'DisplayName', 'Slip-Ring');
-  hold off;
-  legend('Location', 'northeast');
-  xlabel('Time [s]');
-  ylabel('Voltage [V]');
-#+end_src
-
-#+NAME: fig:sr_lpf_geophone_time_on
-#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
-#+begin_src matlab :var filepath="figs/sr_lpf_geophone_time_on.pdf" :var figsize="wide-normal" :post pdf2svg(file=*this*, ext="png")
-  <<plt-matlab>>
-#+end_src
-
-#+NAME: fig:sr_lpf_geophone_time_on
-#+CAPTION: Comparison of the time domain signals when the slip-ring is ON
-#+RESULTS: fig:sr_lpf_geophone_time_on
-[[file:figs/sr_lpf_geophone_time_on.png]]
-
-*** Frequency Domain
-We first compute some parameters that will be used for the PSD computation.
-#+begin_src matlab :results none
-  dt = sr_lpf_off(2, 3)-sr_lpf_off(1, 3);
-
-  Fs = 1/dt; % [Hz]
-
-  win = hanning(ceil(10*Fs));
-#+end_src
-
-Then we compute the Power Spectral Density using =pwelch= function.
-#+begin_src matlab :results none
-  % Direct measure
-  [pxd_lpf_off, ~] = pwelch(sr_lpf_off(:, 1), win, [], [], Fs);
-  [pxd_lpf_on,  ~] = pwelch(sr_lpf_on(:, 1),  win, [], [], Fs);
-
-  % Slip-Ring measure
-  [pxsr_lpf_off, f] = pwelch(sr_lpf_off(:, 2), win, [], [], Fs);
-  [pxsr_lpf_on,  ~] = pwelch(sr_lpf_on(:, 2),  win, [], [], Fs);
-#+end_src
-
-Finally, we compare the Amplitude Spectral Density of the signals (figure [[fig:sr_lpf_geophone_asd]]);
-
-#+begin_src matlab :results none
-  figure;
-  hold on;
-  plot(f, sqrt(pxd_lpf_off), 'DisplayName', 'Direct - OFF');
-  plot(f, sqrt(pxsr_lpf_off), 'DisplayName', 'Slip-Ring - OFF');
-  plot(f, sqrt(pxd_lpf_on),  'DisplayName', 'Direct - ON');
-  plot(f, sqrt(pxsr_lpf_on),  'DisplayName', 'Slip-Ring - ON');
-  hold off;
-  set(gca, 'xscale', 'log');
-  set(gca, 'yscale', 'log');
-  xlabel('Frequency [Hz]'); ylabel('ASD of the measured Voltage $\left[\frac{V}{\sqrt{Hz}}\right]$')
-  legend('Location', 'northeast');
-  xlim([0.1, 500]);
-#+end_src
-
-#+NAME: fig:sr_lpf_geophone_asd
-#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
-#+begin_src matlab :var filepath="figs/sr_lpf_geophone_asd.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
-  <<plt-matlab>>
-#+end_src
-
-#+NAME: fig:sr_lpf_geophone_asd
-#+CAPTION: Comparison of the Amplitude Spectral Sensity
-#+RESULTS: fig:sr_lpf_geophone_asd
-[[file:figs/sr_lpf_geophone_asd.png]]
-
-#+begin_src matlab :results none :exports none
-  xlim([100, 500]);
-#+end_src
-
-#+NAME: fig:sr_lpf_geophone_asd_zoom
-#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
-#+begin_src matlab :var filepath="figs/sr_lpf_geophone_asd_zoom.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
-  <<plt-matlab>>
-#+end_src
-
-#+NAME: fig:sr_lpf_geophone_asd_zoom
-#+CAPTION: Comparison of the Amplitude Spectral Sensity - Zoom
-#+RESULTS: fig:sr_lpf_geophone_asd_zoom
-[[file:figs/sr_lpf_geophone_asd_zoom.png]]
-
-*** Comparison of with and without LPF
-#+begin_src matlab :results none
-  figure;
-  hold on;
-  plot(f, sqrt(pxdon),  'DisplayName', 'Direct - ON');
-  plot(f, sqrt(pxsron),  'DisplayName', 'Slip-Ring - ON');
-  plot(f, sqrt(pxd_lpf_on),  'DisplayName', 'Direct - ON - LPF');
-  plot(f, sqrt(pxsr_lpf_on),  'DisplayName', 'Slip-Ring - ON - LPF');
-  hold off;
-  set(gca, 'xscale', 'log');
-  set(gca, 'yscale', 'log');
-  xlabel('Frequency [Hz]'); ylabel('ASD of the measured Voltage $\left[\frac{V}{\sqrt{Hz}}\right]$')
-  legend('Location', 'northeast');
-  xlim([0.1, 500]);
-#+end_src
-
-#+NAME: fig:comp_with_without_lpf
-#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
-#+begin_src matlab :var filepath="figs/comp_with_without_lpf.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
-  <<plt-matlab>>
-#+end_src
-
-#+NAME: fig:comp_with_without_lpf
-#+CAPTION: Comparison of the measured signals with and without LPF
-#+RESULTS: fig:comp_with_without_lpf
-[[file:figs/comp_with_without_lpf.png]]
-
-*** Conclusion
-#+begin_important
-  - Using the LPF, we don't have any perturbation coming from the slip-ring when it is on.
-  - However, we should use a smaller value of the capacitor to have a cut-off frequency at $1kHz$.
-#+end_important
diff --git a/slip-ring-spindle-vibrations/index.html b/slip-ring-spindle-vibrations/index.html
index a245111..31a2690 100644
--- a/slip-ring-spindle-vibrations/index.html
+++ b/slip-ring-spindle-vibrations/index.html
@@ -3,7 +3,7 @@
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
 <head>
-<!-- 2019-05-13 lun. 13:19 -->
+<!-- 2019-05-13 lun. 13:24 -->
 <meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
 <meta name="viewport" content="width=device-width, initial-scale=1" />
 <title>Vibrations induced by the Slip-Ring and the Spindle</title>
@@ -258,21 +258,21 @@ for the JavaScript code in this tag.
 <h2>Table of Contents</h2>
 <div id="text-table-of-contents">
 <ul>
-<li><a href="#org8c69ce5">1. Experimental Setup</a></li>
-<li><a href="#orgf453912">2. Data Analysis</a>
+<li><a href="#org371ff02">1. Experimental Setup</a></li>
+<li><a href="#orgecddaf0">2. Data Analysis</a>
 <ul>
-<li><a href="#org9872101">2.1. Load data</a></li>
-<li><a href="#org2ae0836">2.2. Time domain plots</a></li>
-<li><a href="#org679ca5d">2.3. Frequency Domain</a></li>
-<li><a href="#org122a9b6">2.4. Conclusion</a></li>
+<li><a href="#orgc4627de">2.1. Load data</a></li>
+<li><a href="#orgb8a6467">2.2. Time domain plots</a></li>
+<li><a href="#org27d9d17">2.3. Frequency Domain</a></li>
+<li><a href="#org6127e14">2.4. Conclusion</a></li>
 </ul>
 </li>
 </ul>
 </div>
 </div>
 
-<div id="outline-container-org8c69ce5" class="outline-2">
-<h2 id="org8c69ce5"><span class="section-number-2">1</span> Experimental Setup</h2>
+<div id="outline-container-org371ff02" class="outline-2">
+<h2 id="org371ff02"><span class="section-number-2">1</span> Experimental Setup</h2>
 <div class="outline-text-2" id="text-1">
 <p>
 All the stages are OFF.
@@ -309,18 +309,79 @@ A first order low pass filter is also added at the input of the voltage amplifie
 <p>
 Three measurements are done:
 </p>
-<ul class="org-ul">
-<li><code>mat/data_024.mat</code>: All the stages are OFF</li>
-<li><code>mat/data_025.mat</code>: The slip-ring is ON and rotates at 6rpm. The spindle is OFF</li>
-<li><code>mat/data_026.mat</code>: The slip-ring and spindle are both ON. They are both turning at 6rpm</li>
-</ul>
+<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
+
+
+<colgroup>
+<col  class="org-left" />
+
+<col  class="org-left" />
+</colgroup>
+<thead>
+<tr>
+<th scope="col" class="org-left">Measurement File</th>
+<th scope="col" class="org-left">Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="org-left"><code>mat/data_024.mat</code></td>
+<td class="org-left">All the stages are OFF</td>
+</tr>
+
+<tr>
+<td class="org-left"><code>mat/data_025.mat</code></td>
+<td class="org-left">The slip-ring is ON and rotates at 6rpm. The spindle is OFF</td>
+</tr>
+
+<tr>
+<td class="org-left"><code>mat/data_026.mat</code></td>
+<td class="org-left">The slip-ring and spindle are both ON. They are both turning at 6rpm</td>
+</tr>
+</tbody>
+</table>
 
 <p>
-A movie showing the experiment is shown on figure <a href="#org02e3283">1</a>.
+Each of the measurement <code>mat</code> file contains one <code>data</code> array with 3 columns:
+</p>
+<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
+
+
+<colgroup>
+<col  class="org-right" />
+
+<col  class="org-left" />
+</colgroup>
+<thead>
+<tr>
+<th scope="col" class="org-right">Column number</th>
+<th scope="col" class="org-left">Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="org-right">1</td>
+<td class="org-left">Geophone - Marble</td>
+</tr>
+
+<tr>
+<td class="org-right">2</td>
+<td class="org-left">Geophone - Sample</td>
+</tr>
+
+<tr>
+<td class="org-right">3</td>
+<td class="org-left">Time</td>
+</tr>
+</tbody>
+</table>
+
+<p>
+A movie showing the experiment is shown on figure <a href="#orgc3a4296">1</a>.
 </p>
 
 
-<div id="org02e3283" class="figure">
+<div id="orgc3a4296" class="figure">
 <p><img src="./img/VID_20190510_155655.gif" alt="VID_20190510_155655.gif" width="300px" />
 </p>
 <p><span class="figure-number">Figure 1: </span>Movie of the experiment, rotation speed is 6rpm</p>
@@ -328,11 +389,11 @@ A movie showing the experiment is shown on figure <a href="#org02e3283">1</a>.
 </div>
 </div>
 
-<div id="outline-container-orgf453912" class="outline-2">
-<h2 id="orgf453912"><span class="section-number-2">2</span> Data Analysis</h2>
+<div id="outline-container-orgecddaf0" class="outline-2">
+<h2 id="orgecddaf0"><span class="section-number-2">2</span> Data Analysis</h2>
 <div class="outline-text-2" id="text-2">
 <p>
-<a id="org611d277"></a>
+<a id="orgc194b61"></a>
 </p>
 
 <div class="note">
@@ -343,8 +404,8 @@ All the files (data and Matlab scripts) are accessible <a href="data/spindle_sli
 </div>
 </div>
 
-<div id="outline-container-org9872101" class="outline-3">
-<h3 id="org9872101"><span class="section-number-3">2.1</span> Load data</h3>
+<div id="outline-container-orgc4627de" class="outline-3">
+<h3 id="orgc4627de"><span class="section-number-3">2.1</span> Load data</h3>
 <div class="outline-text-3" id="text-2-1">
 <div class="org-src-container">
 <pre class="src src-matlab">of = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_024.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; of = of.data;
@@ -355,8 +416,8 @@ sp = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-s
 </div>
 </div>
 
-<div id="outline-container-org2ae0836" class="outline-3">
-<h3 id="org2ae0836"><span class="section-number-3">2.2</span> Time domain plots</h3>
+<div id="outline-container-orgb8a6467" class="outline-3">
+<h3 id="orgb8a6467"><span class="section-number-3">2.2</span> Time domain plots</h3>
 <div class="outline-text-3" id="text-2-2">
 <div class="org-src-container">
 <pre class="src src-matlab"><span class="org-type">figure</span>;
@@ -372,7 +433,7 @@ legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-stri
 </div>
 
 
-<div id="orgacbbef6" class="figure">
+<div id="org914392c" class="figure">
 <p><img src="figs/slip_ring_spindle_marble_time.png" alt="slip_ring_spindle_marble_time.png" />
 </p>
 <p><span class="figure-number">Figure 2: </span>Measurement of the geophone located on the marble - Time domain</p>
@@ -392,7 +453,7 @@ legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-stri
 </div>
 
 
-<div id="org17ed71b" class="figure">
+<div id="orge34f253" class="figure">
 <p><img src="figs/slip_ring_spindle_sample_time.png" alt="slip_ring_spindle_sample_time.png" />
 </p>
 <p><span class="figure-number">Figure 3: </span>Measurement of the geophone at the sample location - Time domain</p>
@@ -400,8 +461,8 @@ legend<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-stri
 </div>
 </div>
 
-<div id="outline-container-org679ca5d" class="outline-3">
-<h3 id="org679ca5d"><span class="section-number-3">2.3</span> Frequency Domain</h3>
+<div id="outline-container-org27d9d17" class="outline-3">
+<h3 id="org27d9d17"><span class="section-number-3">2.3</span> Frequency Domain</h3>
 <div class="outline-text-3" id="text-2-3">
 <p>
 We first compute some parameters that will be used for the PSD computation.
@@ -443,8 +504,8 @@ And for the geophone located at the sample position.
 And we plot the ASD of the measured signals:
 </p>
 <ul class="org-ul">
-<li>figure <a href="#org9c0e002">4</a> for the geophone located on the marble</li>
-<li>figure <a href="#orgfbccecc">5</a> for the geophone at the sample position</li>
+<li>figure <a href="#orgf453585">4</a> for the geophone located on the marble</li>
+<li>figure <a href="#org3aa1b94">5</a> for the geophone at the sample position</li>
 </ul>
 
 <div class="org-src-container">
@@ -463,7 +524,7 @@ xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbo
 </div>
 
 
-<div id="org9c0e002" class="figure">
+<div id="orgf453585" class="figure">
 <p><img src="figs/sr_sp_psd_marble_compare.png" alt="sr_sp_psd_marble_compare.png" />
 </p>
 <p><span class="figure-number">Figure 4: </span>Comparison of the ASD of the measured voltage from the Geophone on the marble</p>
@@ -485,7 +546,7 @@ xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbo
 </div>
 
 
-<div id="orgfbccecc" class="figure">
+<div id="org3aa1b94" class="figure">
 <p><img src="figs/sr_sp_psd_sample_compare.png" alt="sr_sp_psd_sample_compare.png" />
 </p>
 <p><span class="figure-number">Figure 5: </span>Comparison of the ASD of the measured voltage from the Geophone at the sample location</p>
@@ -493,8 +554,8 @@ xlim<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-rainbo
 </div>
 </div>
 
-<div id="outline-container-org122a9b6" class="outline-3">
-<h3 id="org122a9b6"><span class="section-number-3">2.4</span> Conclusion</h3>
+<div id="outline-container-org6127e14" class="outline-3">
+<h3 id="org6127e14"><span class="section-number-3">2.4</span> Conclusion</h3>
 <div class="outline-text-3" id="text-2-4">
 <div class="important">
 <p>
@@ -513,7 +574,7 @@ There is a huge peak at 24Hz on the sample vibration but not on the granite vibr
 </div>
 <div id="postamble" class="status">
 <p class="author">Author: Dehaeze Thomas</p>
-<p class="date">Created: 2019-05-13 lun. 13:19</p>
+<p class="date">Created: 2019-05-13 lun. 13:24</p>
 <p class="validation"><a href="http://validator.w3.org/check?uri=referer">Validate</a></p>
 </div>
 </body>
diff --git a/slip-ring-spindle-vibrations/index.org b/slip-ring-spindle-vibrations/index.org
index 388918a..e9e815a 100644
--- a/slip-ring-spindle-vibrations/index.org
+++ b/slip-ring-spindle-vibrations/index.org
@@ -19,9 +19,18 @@ A first order low pass filter is also added at the input of the voltage amplifie
 - Identify the vibrations induced by the rotation of the Slip-Ring and Spindle
 
 Three measurements are done:
-- =mat/data_024.mat=: All the stages are OFF
-- =mat/data_025.mat=: The slip-ring is ON and rotates at 6rpm. The spindle is OFF
-- =mat/data_026.mat=: The slip-ring and spindle are both ON. They are both turning at 6rpm
+| Measurement File   | Description                                                          |
+|--------------------+----------------------------------------------------------------------|
+| =mat/data_024.mat= | All the stages are OFF                                               |
+| =mat/data_025.mat= | The slip-ring is ON and rotates at 6rpm. The spindle is OFF          |
+| =mat/data_026.mat= | The slip-ring and spindle are both ON. They are both turning at 6rpm |
+
+Each of the measurement =mat= file contains one =data= array with 3 columns:
+| Column number | Description       |
+|---------------+-------------------|
+|             1 | Geophone - Marble |
+|             2 | Geophone - Sample |
+|             3 | Time              |
 
 A movie showing the experiment is shown on figure [[fig:exp_sl_sp_gif]].
 
