Add slip-ring analysis
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Library/figs/.gitignore
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Library/figs/.gitignore
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*.pdf
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*.tex
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Library/figs/slipring_asd.png
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Library/figs/slipring_asd.png
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Library/figs/slipring_time.png
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#+TITLE:Measurements
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:DRAWER:
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#+STARTUP: overview
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#+HTML_HEAD: <link rel="stylesheet" type="text/css" href="../css/htmlize.css"/>
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#+HTML_HEAD: <link rel="stylesheet" type="text/css" href="../css/readtheorg.css"/>
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#+HTML_HEAD: <link rel="stylesheet" type="text/css" href="../css/zenburn.css"/>
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#+HTML_HEAD: <script type="text/javascript" src="../js/jquery.min.js"></script>
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#+HTML_HEAD: <script type="text/javascript" src="../js/bootstrap.min.js"></script>
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#+HTML_HEAD: <script type="text/javascript" src="../js/jquery.stickytableheaders.min.js"></script>
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#+HTML_HEAD: <script type="text/javascript" src="../js/readtheorg.js"></script>
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#+PROPERTY: header-args:matlab :session *MATLAB*
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#+PROPERTY: header-args:matlab+ :comments org
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#+PROPERTY: header-args:matlab+ :results output
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#+PROPERTY: header-args:matlab+ :exports both
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#+PROPERTY: header-args:matlab+ :eval no-export
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#+PROPERTY: header-args:matlab+ :output-dir figs
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:END:
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For all the measurements here, the geophones are L22.
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The signals are amplified with voltage amplifiers with a gain of 60dB.
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The voltage amplifiers include a low pass filter with a cut-off frequency at 1kHz.
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* Effect of the control system of each stage
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** Experimental Setup
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One geophone is on the marble, the other at the sample location (see figures below).
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The signal from the top geophone goes through the slip-ring.
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The signals from the geophones are amplified by a voltage amplifier with a gain of 60dB.
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The voltage amplifier also include a low pass filter with a corner frequency of 1kHz.
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#+name: fig:setup_ty_1
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#+caption: Figure caption
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#+attr_html: :width 500px
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[[file:./img/IMG_20190430_112613.jpg]]
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#+name: fig:setup_ty_2
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#+caption: Figure caption
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#+attr_html: :width 500px
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[[file:./img/IMG_20190430_112615.jpg]]
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#+name: fig:setup_ty_3
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#+caption: Figure caption
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#+attr_html: :width 500px
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[[file:./img/IMG_20190430_112620.jpg]]
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Two measurements are done:
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| Setup | Data File |
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|----------------------+--------------------|
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| Control of Ty is on | =mat/data_001.mat= |
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| Control of Ty is off | =mat/data_002.mat= |
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For each of the measurements
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| Variable | Description |
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|----------+--------------------------------------------------------------------|
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| =t= | Time Vector |
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| =x1= | Voltage measured across the geophone placed on the marble |
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| =x2= | Voltage measured across the geophone placed at the sample location |
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Measurements are 50s long.
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** Matlab Init :noexport:ignore:
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#+begin_src matlab :exports none :results silent :noweb yes
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<<matlab-init>>
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#+end_src
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** Load data
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We load the data of the z axis of two geophones.
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#+begin_src matlab :results none
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tyOn = load('mat/data_001.mat', 't', 'x1', 'x2');
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tyOff = load('mat/data_002.mat', 't', 'x1', 'x2');
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#+end_src
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** Analysis
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#+begin_src matlab :results none
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dt = tyOn.t(2)-tyOn.t(1);
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Fs = 1/dt;
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#+end_src
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#+begin_src matlab :results none
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figure;
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hold on;
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plot(tyOn.t, tyOn.x1);
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plot(tyOn.t, tyOn.x2);
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hold off;
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legend({'x1 - ON', 'x2 - ON'});
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#+end_src
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#+begin_src matlab :results none
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figure;
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hold on;
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plot(tyOff.t, tyOff.x1);
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plot(tyOff.t, tyOff.x2);
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hold off;
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legend({'x1 - OFF', 'x2 - OFF'});
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#+end_src
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#+begin_src matlab :results none
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Fs = 1/dt;
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win = hanning(ceil(10*Fs));
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#+end_src
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#+begin_src matlab :results none
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[pxOn1, f] = pwelch(tyOn.x1, win, [], [], Fs);
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[pxOn2, ~] = pwelch(tyOn.x2, win, [], [], Fs);
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[pxOff1, ~] = pwelch(tyOff.x1, win, [], [], Fs);
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[pxOff2, ~] = pwelch(tyOff.x2, win, [], [], Fs);
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#+end_src
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#+begin_src matlab :results none
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figure;
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hold on;
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plot(f, sqrt(pxOn1));
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plot(f, sqrt(pxOn2));
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hold off;
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set(gca, 'xscale', 'log');
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set(gca, 'yscale', 'log');
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xlabel('Frequency [Hz]'); ylabel('PSD [m/s/sqrt(Hz)]')
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% xlim([2, 500]);
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#+end_src
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#+begin_src matlab :results none
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figure;
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hold on;
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plot(f, sqrt(pxOn1));
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plot(f, sqrt(pxOff1));
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hold off;
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set(gca, 'xscale', 'log');
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set(gca, 'yscale', 'log');
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xlabel('Frequency [Hz]'); ylabel('PSD [m/s/sqrt(Hz)]')
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% xlim([2, 500]);
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#+end_src
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#+begin_src matlab :results none
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figure;
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hold on;
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plot(f, sqrt(pxOn2));
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plot(f, sqrt(pxOff2));
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hold off;
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set(gca, 'xscale', 'log');
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set(gca, 'yscale', 'log');
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xlabel('Frequency [Hz]'); ylabel('PSD [m/s/sqrt(Hz)]')
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% xlim([2, 500]);
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#+end_src
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#+begin_src matlab :results none
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[T_off, ~] = tfestimate(tyOff.x1, tyOff.x2, win, [], [], Fs);
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[coh_off, ~] = mscohere(tyOff.x1, tyOff.x2, win, [], [], Fs);
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[T_on, ~] = tfestimate(tyOn.x1, tyOn.x2, win, [], [], Fs);
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[coh_on, ~] = mscohere(tyOn.x1, tyOn.x2, win, [], [], Fs);
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#+end_src
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#+begin_src matlab :results none :exports none
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figure;
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hold on;
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plot(f, coh_on);
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plot(f, coh_off);
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hold off;
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set(gca, 'xscale', 'log');
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xlabel('Frequency [Hz]'); ylabel('Coherence');
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ylim([0,1]); xlim([1, 500]);
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#+end_src
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#+begin_src matlab :results none :exports none
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figure;
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ax1 = subplot(2, 1, 1);
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hold on;
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plot(f, abs(T_on));
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plot(f, abs(T_off));
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hold off;
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set(gca, 'xscale', 'log'); set(gca, 'yscale', 'log');
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set(gca, 'XTickLabel',[]);
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ylabel('Magnitude');
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ax2 = subplot(2, 1, 2);
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hold on;
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plot(f, mod(180+180/pi*phase(T_on), 360)-180);
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plot(f, mod(180+180/pi*phase(T_off), 360)-180);
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hold off;
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set(gca, 'xscale', 'log');
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ylim([-180, 180]);
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yticks([-180, -90, 0, 90, 180]);
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xlabel('Frequency [Hz]'); ylabel('Phase');
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linkaxes([ax1,ax2],'x');
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xlim([1, 500]);
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#+end_src
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* Effect of the Slip-Ring on the signal
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** Experimental Setup
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Two measurements are made where the control of all the stages are OFF.
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One geophone is located on the marble while the other is located at the sample location.
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The two measurements are:
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| Measurement File | Description |
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|------------------+------------------------------------------------------------------|
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| =meas_008.mat= | Signal from the top geophone does not goes through the Slip-ring |
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| =meas_009.mat= | Signal goes through the Slip-ring |
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Each of the measurement =mat= file contains one =data= array with 3 columns:
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| Column number | Description |
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|---------------+-------------------|
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| 1 | Geophone - Marble |
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| 2 | Geophone - Sample |
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| 3 | Time |
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** Matlab Init :noexport:ignore:
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#+begin_src matlab :exports none :results silent :noweb yes
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<<matlab-init>>
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#+end_src
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** Load data
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We load the data of the z axis of two geophones.
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#+begin_src matlab :results none
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data8 = load('mat/data_008.mat', 'data');
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data9 = load('mat/data_009.mat', 'data');
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#+end_src
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** Analysis - Time Domain
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#+begin_src matlab :results none
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figure;
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hold on;
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plot(data9.data(:, 3), data9.data(:, 2), 'DisplayName', 'Slip-Ring');
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plot(data8.data(:, 3), data8.data(:, 2), 'DisplayName', 'Wire');
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hold off;
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xlabel('Time [s]'); ylabel('Voltage [V]');
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xlim([0, 50]);
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legend();
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#+end_src
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#+NAME: fig:slipring_time
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#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
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#+begin_src matlab :var filepath="figs/slipring_time.pdf" :var figsize="wide-tall" :post pdf2svg(file=*this*, ext="png")
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<<plt-matlab>>
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#+end_src
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#+NAME: fig:slipring_time
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#+CAPTION: Effect of the Slip-Ring on the measured signal - Time domain
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#+RESULTS: fig:slipring_time
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[[file:figs/slipring_time.png]]
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** Analysis - Frequency Domain
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#+begin_src matlab :results none
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dt = data8.data(2, 3) - data8.data(1, 3);
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Fs = 1/dt;
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win = hanning(ceil(1*Fs));
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#+end_src
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#+begin_src matlab :results none
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[pxx8, f] = pwelch(data8.data(:, 2), win, [], [], Fs);
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[pxx9, ~] = pwelch(data9.data(:, 2), win, [], [], Fs);
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#+end_src
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#+begin_src matlab :results none
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figure;
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hold on;
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plot(f, sqrt(pxx9), 'DisplayName', 'Slip-Ring');
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plot(f, sqrt(pxx8), 'DisplayName', 'Wire');
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hold off;
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set(gca, 'xscale', 'log');
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set(gca, 'yscale', 'log');
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xlabel('Frequency [Hz]'); ylabel('ASD [V/sqrt(Hz)]')
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xlim([1, 500]);
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legend('Location', 'southwest');
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#+end_src
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#+NAME: fig:slipring_asd
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#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
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#+begin_src matlab :var filepath="figs/slipring_asd.pdf" :var figsize="wide-tall" :post pdf2svg(file=*this*, ext="png")
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<<plt-matlab>>
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#+end_src
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#+NAME: fig:slipring_asd
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#+CAPTION: Effect of the Slip-Ring on the measured signal - Frequency domain
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#+RESULTS: fig:slipring_asd
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[[file:figs/slipring_asd.png]]
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** Conclusion
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*Remaining questions to answer*:
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- Why is there a sharp peak at 300Hz?
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- Why the use of the Slip-Ring does induce a noise?
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- Can the capacitive/inductive properties of the wires in the Slip-ring does not play well with the geophone? (resonant RLC circuit)
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* Measurement when signal from top geophone does not go trought the slip-ring
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| Ty | Ry | Slip Ring | Spindle | Hexapod | Meas. file |
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|------+------+-----------+---------+---------+----------------|
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| *ON* | *ON* | *ON* | *ON* | *ON* | =meas_003.mat= |
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| OFF | *ON* | *ON* | *ON* | *ON* | =meas_004.mat= |
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| OFF | OFF | *ON* | *ON* | *ON* | =meas_005.mat= |
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| OFF | OFF | OFF | *ON* | *ON* | =meas_006.mat= |
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| OFF | OFF | OFF | OFF | *ON* | =meas_007.mat= |
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| OFF | OFF | OFF | OFF | OFF | =meas_008.mat= |
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