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<div id="content">
<h1 class="title">Measurements</h1>
<div id="table-of-contents">
<h2>Table of Contents</h2>
<div id="text-table-of-contents">
<ul>
<li><a href="#org0ba7d8d">1. Effect of the rotation of the Slip-Ring</a>
<ul>
<li><a href="#orgac49742">1.1. Measurement Description</a></li>
<li><a href="#org6434d5d">1.2. Load data</a></li>
<li><a href="#orga93c712">1.3. Analysis</a></li>
<li><a href="#org87e1c5d">1.4. Conclusion</a></li>
</ul>
</li>
<li><a href="#org3930587">2. Measure of the noise of the Voltage Amplifier</a>
<ul>
<li><a href="#org39ab0d4">2.1. Measurement Description</a></li>
<li><a href="#org05e21ac">2.2. Load data</a></li>
<li><a href="#org94d0313">2.3. Time Domain</a></li>
<li><a href="#org4ce7550">2.4. Frequency Domain</a></li>
<li><a href="#orgddca579">2.5. Conclusion</a></li>
</ul>
</li>
<li><a href="#orgda176e9">3. Measure of the noise induced by the Slip-Ring</a>
<ul>
<li><a href="#org0c723ab">3.1. Measurement Description</a></li>
<li><a href="#orgb59af10">3.2. Load data</a></li>
<li><a href="#orgfa16ec5">3.3. Time Domain</a></li>
<li><a href="#orge0c2b75">3.4. Frequency Domain</a></li>
<li><a href="#org42e6a09">3.5. Conclusion</a></li>
</ul>
</li>
<li><a href="#org2d68753">4. Measure of the noise induced by the slip ring when using a geophone</a>
<ul>
<li><a href="#org3d4e974">4.1. Measurement Description</a></li>
<li><a href="#org727e79c">4.2. Load data</a></li>
<li><a href="#orge2a10ee">4.3. Time Domain</a></li>
<li><a href="#org6939b54">4.4. Frequency Domain</a></li>
<li><a href="#org05104a8">4.5. Conclusion</a></li>
</ul>
</li>
<li><a href="#org4f273de">5. Measure of the influence of the AC/DC option on the voltage amplifiers</a>
<ul>
<li><a href="#orgbdff313">5.1. Measurement Description</a></li>
<li><a href="#org002ef0d">5.2. Load data</a></li>
<li><a href="#orgf18b42c">5.3. Time Domain</a></li>
<li><a href="#org7ad219b">5.4. Frequency Domain</a></li>
<li><a href="#org030a799">5.5. Conclusion</a></li>
</ul>
</li>
</ul>
</div>
</div>
<div id="outline-container-org0ba7d8d" class="outline-2">
<h2 id="org0ba7d8d"><span class="section-number-2">1</span> Effect of the rotation of the Slip-Ring</h2>
<div class="outline-text-2" id="text-1">
<p>
The data and matlab files are accessible <a href="data/meas_effect_sr.zip">here</a>.
</p>
</div>
<div id="outline-container-orgac49742" class="outline-3">
<h3 id="orgac49742"><span class="section-number-3">1.1</span> Measurement Description</h3>
<div class="outline-text-3" id="text-1-1">
<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-org6434d5d" class="outline-3">
<h3 id="org6434d5d"><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">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-orga93c712" class="outline-3">
<h3 id="orga93c712"><span class="section-number-3">1.3</span> Analysis</h3>
<div class="outline-text-3" id="text-1-3">
<p>
Let's first look at the signal produced by the DAC (figure <a href="#org3aa5fe7">1</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="org3aa5fe7" class="figure">
<p><img src="figs/random_signal.png" alt="random_signal.png" />
</p>
<p><span class="figure-number">Figure 1: </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="#orgb56de9a">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>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="orgb56de9a" class="figure">
<p><img src="figs/slipring_comp_signals.png" alt="slipring_comp_signals.png" />
</p>
<p><span class="figure-number">Figure 2: </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="org6682917" class="figure">
<p><img src="figs/psd_noise.png" alt="psd_noise.png" />
</p>
<p><span class="figure-number">Figure 3: </span>ASD of the measured noise</p>
</div>
</div>
</div>
<div id="outline-container-org87e1c5d" class="outline-3">
<h3 id="org87e1c5d"><span class="section-number-3">1.4</span> Conclusion</h3>
<div class="outline-text-3" id="text-1-4">
<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-org3930587" class="outline-2">
<h2 id="org3930587"><span class="section-number-2">2</span> Measure of the noise of the Voltage Amplifier</h2>
<div class="outline-text-2" id="text-2">
<p>
The data and matlab files are accessible <a href="data/meas_volt_amp.zip">here</a>.
</p>
</div>
<div id="outline-container-org39ab0d4" class="outline-3">
<h3 id="org39ab0d4"><span class="section-number-3">2.1</span> Measurement Description</h3>
<div class="outline-text-3" id="text-2-1">
<p>
<b>Goal</b>:
</p>
<ul class="org-ul">
<li>Determine the Voltage Amplifier noise</li>
</ul>
<p>
<b>Setup</b>:
</p>
<ul class="org-ul">
<li>The two inputs (differential) of the voltage amplifier are shunted with 50Ohms</li>
<li>The AC/DC option of the Voltage amplifier is on AC</li>
<li>The low pass filter is set to 1hHz</li>
<li>We measure the output of the voltage amplifier with a 16bits ADC of the Speedgoat</li>
</ul>
<p>
<b>Measurements</b>:
</p>
<ul class="org-ul">
<li><code>data_003</code>: Ampli OFF</li>
<li><code>data_004</code>: Ampli ON set to 20dB</li>
<li><code>data_005</code>: Ampli ON set to 40dB</li>
<li><code>data_006</code>: Ampli ON set to 60dB</li>
</ul>
</div>
</div>
<div id="outline-container-org05e21ac" class="outline-3">
<h3 id="org05e21ac"><span class="section-number-3">2.2</span> Load data</h3>
<div class="outline-text-3" id="text-2-2">
<div class="org-src-container">
<pre class="src src-matlab">amp_off = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_003.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; amp_off = amp_off.data<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-type">:</span>, <span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">1</span>,<span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
amp_20d = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_004.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; amp_20d = amp_20d.data<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-type">:</span>, <span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">1</span>,<span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
amp_40d = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_005.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; amp_40d = amp_40d.data<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-type">:</span>, <span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">1</span>,<span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
amp_60d = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_006.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; amp_60d = amp_60d.data<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-type">:</span>, <span class="org-rainbow-delimiters-depth-2">[</span><span class="org-highlight-numbers-number">1</span>,<span class="org-highlight-numbers-number">3</span><span class="org-rainbow-delimiters-depth-2">]</span><span class="org-rainbow-delimiters-depth-1">)</span>;
</pre>
</div>
</div>
</div>
<div id="outline-container-org94d0313" class="outline-3">
<h3 id="org94d0313"><span class="section-number-3">2.3</span> Time Domain</h3>
<div class="outline-text-3" id="text-2-3">
<p>
The time domain signals are shown on figure <a href="#org0ba0324">4</a>.
</p>
<div id="org0ba0324" class="figure">
<p><img src="figs/ampli_noise_time.png" alt="ampli_noise_time.png" />
</p>
<p><span class="figure-number">Figure 4: </span>Output of the amplifier</p>
</div>
</div>
</div>
<div id="outline-container-org4ce7550" class="outline-3">
<h3 id="org4ce7550"><span class="section-number-3">2.4</span> Frequency Domain</h3>
<div class="outline-text-3" id="text-2-4">
<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 = amp_off<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">2</span>, <span class="org-highlight-numbers-number">2</span><span class="org-rainbow-delimiters-depth-1">)</span><span class="org-type">-</span>amp_off<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-highlight-numbers-number">1</span>, <span class="org-highlight-numbers-number">2</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>pxoff, f<span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>amp_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>px20d, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>amp_20d<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>px40d, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>amp_40d<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>px60d, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>amp_60d<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>;
</pre>
</div>
<p>
We compute the theoretical ADC noise.
</p>
<div class="org-src-container">
<pre class="src src-matlab">q = <span class="org-highlight-numbers-number">20</span><span class="org-type">/</span><span class="org-highlight-numbers-number">2</span><span class="org-type">^</span><span class="org-highlight-numbers-number">16</span>; <span class="org-comment">% quantization</span>
Sq = q<span class="org-type">^</span><span class="org-highlight-numbers-number">2</span><span class="org-type">/</span><span class="org-highlight-numbers-number">12</span><span class="org-type">/</span><span class="org-highlight-numbers-number">1000</span>; <span class="org-comment">% PSD of the ADC noise</span>
</pre>
</div>
<p>
Finally, the ASD is shown on figure <a href="#org9677595">5</a>.
</p>
<div id="org9677595" class="figure">
<p><img src="figs/ampli_noise_psd.png" alt="ampli_noise_psd.png" />
</p>
<p><span class="figure-number">Figure 5: </span>Amplitude Spectral Density of the measured voltage at the output of the voltage amplifier</p>
</div>
</div>
</div>
<div id="outline-container-orgddca579" class="outline-3">
<h3 id="orgddca579"><span class="section-number-3">2.5</span> Conclusion</h3>
<div class="outline-text-3" id="text-2-5">
<div class="important">
<p>
Noise induced by the voltage amplifiers is not a limiting factor.
</p>
</div>
</div>
</div>
</div>
<div id="outline-container-orgda176e9" class="outline-2">
<h2 id="orgda176e9"><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>
The data and matlab files are accessible <a href="data/meas_slip_ring.zip">here</a>.
</p>
</div>
<div id="outline-container-org0c723ab" class="outline-3">
<h3 id="org0c723ab"><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="org7c8c12d" class="figure">
<p><img src="./img/VID_20190503_160831.gif" alt="VID_20190503_160831.gif" />
</p>
<p><span class="figure-number">Figure 6: </span>Slip-Ring rotating at 6rpm</p>
</div>
<div id="org507a4c4" class="figure">
<p><img src="./img/VID_20190503_161401.gif" alt="VID_20190503_161401.gif" />
</p>
<p><span class="figure-number">Figure 7: </span>Slip-Ring rotating at 60rpm</p>
</div>
</div>
</div>
<div id="outline-container-orgb59af10" class="outline-3">
<h3 id="orgb59af10"><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-orgfa16ec5" class="outline-3">
<h3 id="orgfa16ec5"><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="#orgf5bca83">8</a>) and for the signal going through the slip-ring (figure <a href="#org6570f49">9</a>);
</p>
<div id="orgf5bca83" class="figure">
<p><img src="figs/sr_direct_time.png" alt="sr_direct_time.png" />
</p>
<p><span class="figure-number">Figure 8: </span>Direct measurement</p>
</div>
<div id="org6570f49" class="figure">
<p><img src="figs/sr_slipring_time.png" alt="sr_slipring_time.png" />
</p>
<p><span class="figure-number">Figure 9: </span>Measurement of the signal going through the Slip-Ring</p>
</div>
</div>
</div>
<div id="outline-container-orge0c2b75" class="outline-3">
<h3 id="orge0c2b75"><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="#org1bfaa20">10</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="org1bfaa20" class="figure">
<p><img src="figs/sr_psd_compare.png" alt="sr_psd_compare.png" />
</p>
<p><span class="figure-number">Figure 10: </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-org42e6a09" class="outline-3">
<h3 id="org42e6a09"><span class="section-number-3">3.5</span> Conclusion</h3>
<div class="outline-text-3" id="text-3-5">
<div class="important">
<p>
</p>
</div>
</div>
</div>
</div>
<div id="outline-container-org2d68753" class="outline-2">
<h2 id="org2d68753"><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>
The data and matlab files are accessible <a href="data/meas_sr_geophone.zip">here</a>.
</p>
</div>
<div id="outline-container-org3d4e974" class="outline-3">
<h3 id="org3d4e974"><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 if the noise induced by the slip-ring is a limiting factor when measuring the signal coming from a geophone</li>
</ul>
<p>
<b>Setup</b>:
</p>
<ul class="org-ul">
<li>The geophone is located at the sample location</li>
<li>The two Voltage amplifiers have the following settings:
<ul class="org-ul">
<li>AC</li>
<li>60dB</li>
<li>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=>voltage amplifier=>ADC.</li>
</ul></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_012</code>: Slip-Ring OFF</li>
<li><code>data_013</code>: Slip-Ring ON</li>
</ul>
</div>
</div>
<div id="outline-container-org727e79c" class="outline-3">
<h3 id="org727e79c"><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_012.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><span class="org-string">'mat/data_013.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; sr_on = sr_on.data;
</pre>
</div>
</div>
</div>
<div id="outline-container-orge2a10ee" class="outline-3">
<h3 id="orge2a10ee"><span class="section-number-3">4.3</span> Time Domain</h3>
<div class="outline-text-3" id="text-4-3">
<p>
We compare the signal when the Slip-Ring is OFF (figure <a href="#org098ac5b">11</a>) and when it is ON (figure <a href="#org2847280">12</a>).
</p>
<div id="org098ac5b" class="figure">
<p><img src="figs/sr_geophone_time_off.png" alt="sr_geophone_time_off.png" />
</p>
<p><span class="figure-number">Figure 11: </span>Comparison of the time domain signals when the slip-ring is OFF</p>
</div>
<div id="org2847280" class="figure">
<p><img src="figs/sr_geophone_time_on.png" alt="sr_geophone_time_on.png" />
</p>
<p><span class="figure-number">Figure 12: </span>Comparison of the time domain signals when the slip-ring is ON</p>
</div>
</div>
</div>
<div id="outline-container-org6939b54" class="outline-3">
<h3 id="org6939b54"><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-comment">% Direct measure</span>
<span class="org-rainbow-delimiters-depth-1">[</span>pxdoff, <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">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>pxdon, <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">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-comment">% Slip-Ring measure</span>
<span class="org-rainbow-delimiters-depth-1">[</span>pxsroff, 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">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>pxsron, <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>;
</pre>
</div>
<p>
Finally, we compare the Amplitude Spectral Density of the signals (figure [[]]);
</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>pxdoff<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>pxsroff<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>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>;
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="org5b61df7" class="figure">
<p><img src="figs/sr_geophone_asd.png" alt="sr_geophone_asd.png" />
</p>
<p><span class="figure-number">Figure 13: </span>Comparison of the Amplitude Spectral Sensity</p>
</div>
<div id="org0d244aa" class="figure">
<p><img src="figs/sr_geophone_asd_zoom.png" alt="sr_geophone_asd_zoom.png" />
</p>
<p><span class="figure-number">Figure 14: </span>Comparison of the Amplitude Spectral Sensity - Zoom</p>
</div>
</div>
</div>
<div id="outline-container-org05104a8" class="outline-3">
<h3 id="org05104a8"><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>When the slip-ring is OFF, it does not add any noise to the measurement</li>
<li>When the slip-ring is ON, it adds significant noise to the signal</li>
</ul>
</div>
</div>
</div>
</div>
<div id="outline-container-org4f273de" class="outline-2">
<h2 id="org4f273de"><span class="section-number-2">5</span> Measure of the influence of the AC/DC option on the voltage amplifiers</h2>
<div class="outline-text-2" id="text-5">
<p>
The data and matlab files are accessible <a href="data/meas_noise_ac_dc.zip">here</a>.
</p>
</div>
<div id="outline-container-orgbdff313" class="outline-3">
<h3 id="orgbdff313"><span class="section-number-3">5.1</span> Measurement Description</h3>
<div class="outline-text-3" id="text-5-1">
<p>
<b>Goal</b>:
</p>
<ul class="org-ul">
<li>Measure the influence of the high-pass filter option of the voltage amplifiers</li>
</ul>
<p>
<b>Setup</b>:
</p>
<ul class="org-ul">
<li>One geophone is located on the marble.</li>
<li>It's signal goes to two voltage amplifiers with a gain of 60dB.</li>
<li>One voltage amplifier is on the AC option, the other is on the DC option.</li>
</ul>
<p>
<b>Measurements</b>:
First measurement (<code>mat/data_014.mat</code> file):
</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</th>
<th scope="col" class="org-left">Signal</th>
</tr>
</thead>
<tbody>
<tr>
<td class="org-right">1</td>
<td class="org-left">Amplifier 1 with AC option</td>
</tr>
<tr>
<td class="org-right">2</td>
<td class="org-left">Amplifier 2 with DC option</td>
</tr>
<tr>
<td class="org-right">3</td>
<td class="org-left">Time</td>
</tr>
</tbody>
</table>
<p>
Second measurement (<code>mat/data_015.mat</code> file):
</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</th>
<th scope="col" class="org-left">Signal</th>
</tr>
</thead>
<tbody>
<tr>
<td class="org-right">1</td>
<td class="org-left">Amplifier 1 with DC option</td>
</tr>
<tr>
<td class="org-right">2</td>
<td class="org-left">Amplifier 2 with AC option</td>
</tr>
<tr>
<td class="org-right">3</td>
<td class="org-left">Time</td>
</tr>
</tbody>
</table>
<div id="orgff33e23" class="figure">
<p><img src="./img/IMG_20190503_170936.jpg" alt="IMG_20190503_170936.jpg" width="500px" />
</p>
<p><span class="figure-number">Figure 15: </span>Picture of the two voltages amplifiers</p>
</div>
</div>
</div>
<div id="outline-container-org002ef0d" class="outline-3">
<h3 id="org002ef0d"><span class="section-number-3">5.2</span> Load data</h3>
<div class="outline-text-3" id="text-5-2">
<p>
We load the data of the z axis of two geophones.
</p>
<div class="org-src-container">
<pre class="src src-matlab">meas14 = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_014.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; meas14 = meas14.data;
meas15 = load<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-string">'mat/data_015.mat', 'data'</span><span class="org-rainbow-delimiters-depth-1">)</span>; meas15 = meas15.data;
</pre>
</div>
</div>
</div>
<div id="outline-container-orgf18b42c" class="outline-3">
<h3 id="orgf18b42c"><span class="section-number-3">5.3</span> Time Domain</h3>
<div class="outline-text-3" id="text-5-3">
<p>
The signals are shown on figure <a href="#orge57d23e">16</a>.
</p>
<div id="orge57d23e" class="figure">
<p><img src="figs/ac_dc_option_time.png" alt="ac_dc_option_time.png" />
</p>
<p><span class="figure-number">Figure 16: </span>Comparison of the signals going through the Voltage amplifiers</p>
</div>
</div>
</div>
<div id="outline-container-org7ad219b" class="outline-3">
<h3 id="org7ad219b"><span class="section-number-3">5.4</span> Frequency Domain</h3>
<div class="outline-text-3" id="text-5-4">
<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 = meas14<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>meas14<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>pxamp1ac, f<span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>meas14<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>pxamp2dc, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>meas14<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>pxamp1dc, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>meas15<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>pxamp2ac, <span class="org-type">~</span><span class="org-rainbow-delimiters-depth-1">]</span> = pwelch<span class="org-rainbow-delimiters-depth-1">(</span>meas15<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>
The ASD of the signals are compare on figure <a href="#org0650c5f">17</a>.
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<p><img src="figs/ac_dc_option_asd.png" alt="ac_dc_option_asd.png" />
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<p><span class="figure-number">Figure 17: </span>Amplitude Spectral Density of the measured signals</p>
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<h3 id="org030a799"><span class="section-number-3">5.5</span> Conclusion</h3>
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<p class="author">Author: Thomas Dehaeze</p>
<p class="date">Created: 2019-05-06 lun. 14:16</p>
<p class="validation"><a href="http://validator.w3.org/check?uri=referer">Validate</a></p>
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