Add analysis on the new measurements

slip-ring-test/index.org

@@ -166,12 +166,14 @@ We now look at the difference between the signal directly measured by the ADC an
   :END:
 
 #+begin_src bash :exports none :results none
-  zip data/meas_volt_amp \
-      mat/data_003.mat \
-      mat/data_004.mat \
-      mat/data_005.mat \
-      mat/data_006.mat \
-      meas_volt_amp.m
+  if [ meas_volt_amp.m -nt data/meas_volt_amp.zip ]; then
+    zip data/meas_volt_amp \
+        mat/data_003.mat \
+        mat/data_004.mat \
+        mat/data_005.mat \
+        mat/data_006.mat \
+        meas_volt_amp.m
+  fi
 #+end_src
 
 The data and matlab files are accessible [[file:data/meas_volt_amp.zip][here]].
@@ -286,7 +288,10 @@ Finally, the ASD is shown on figure [[fig:ampli_noise_psd]].
 
 ** Conclusion
 #+begin_important
-  Noise induced by the voltage amplifiers is not a limiting factor.
+  *Questions*:
+  - Where does those sharp peaks comes from? Can this be due to aliasing?
+
+  Noise induced by the voltage amplifiers seems not to be a limiting factor as we have the same noise when they are OFF and ON.
 #+end_important
 
 * Measure of the noise induced by the Slip-Ring
@@ -296,12 +301,14 @@ Finally, the ASD is shown on figure [[fig:ampli_noise_psd]].
   :END:
 
 #+begin_src bash :exports none :results none
-  zip data/meas_slip_ring \
-      mat/data_008.mat \
-      mat/data_009.mat \
-      mat/data_010.mat \
-      mat/data_011.mat \
-      meas_slip_ring.m
+  if [ meas_slip_ring.m -nt data/meas_slip_ring.zip ]; then
+    zip data/meas_slip_ring \
+        mat/data_008.mat \
+        mat/data_009.mat \
+        mat/data_010.mat \
+        mat/data_011.mat \
+        meas_slip_ring.m
+  fi
 #+end_src
 
 The data and matlab files are accessible [[file:data/meas_slip_ring.zip][here]].
@@ -449,7 +456,9 @@ And we plot the ASD of the measured signals (figure [[fig:sr_psd_compare]]);
 
 ** Conclusion
 #+begin_important
-
+  *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
 
 * Measure of the noise induced by the slip ring when using a geophone
@@ -459,12 +468,14 @@ And we plot the ASD of the measured signals (figure [[fig:sr_psd_compare]]);
   :END:
 
 #+begin_src bash :exports none :results none
-  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
+  if [ meas_sr_geophone.m -nt data/meas_sr_geophone.zip ]; then
+    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
+  fi
 #+end_src
 
 The data and matlab files are accessible [[file:data/meas_sr_geophone.zip][here]].
@@ -647,7 +658,7 @@ Then the Slip-Ring is OFF, we don't observe this 40kHz anymore (figure [[fig:osc
 #+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.
+  - 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
@@ -812,7 +823,7 @@ Finally, we compare the Amplitude Spectral Density of the signals (figure [[fig:
 *** Conclusion
 #+begin_important
   - Using the LPF, we don't have any perturbation coming from the slip-ring when it is on.
-  - However, we will use a smaller value of the capacitor to have a cut-off frequency at $1kHz$.
+  - However, we should use a smaller value of the capacitor to have a cut-off frequency at $1kHz$.
 #+end_important
 
 * Measure of the influence of the AC/DC option on the voltage amplifiers
@@ -822,10 +833,12 @@ Finally, we compare the Amplitude Spectral Density of the signals (figure [[fig:
   :END:
 
 #+begin_src bash :exports none :results none
-  zip data/meas_noise_ac_dc \
-      mat/data_012.mat \
-      mat/data_013.mat \
-      meas_noise_ac_dc.m
+  if [ meas_noise_ac_dc.m -nt data/meas_noise_ac_dc.zip ]; then
+    zip data/meas_noise_ac_dc \
+        mat/data_012.mat \
+        mat/data_013.mat \
+        meas_noise_ac_dc.m
+  fi
 #+end_src
 
 The data and matlab files are accessible [[file:data/meas_noise_ac_dc.zip][here]].
@@ -948,13 +961,27 @@ The ASD of the signals are compare on figure [[fig:ac_dc_option_asd]].
 #+begin_important
   - The voltage amplifiers include some very sharp high pass filters at 1.5Hz (maybe 4th order)
   - There is a DC offset on the time domain signal because the DC-offset knob was not set to zero
-
-  *Questions*:
-  - What option should be used for the measurements?
 #+end_important
 
-* Measure of the Low Pass Filter
-** Measurement Description
+* Transfer function of the Low Pass Filter
+  :PROPERTIES:
+  :header-args:matlab+: :tangle low_pass_filter_measurements.m
+  :header-args:matlab+: :comments org :mkdirp yes
+  :END:
+
+#+begin_src bash :exports none :results none
+  if [ low_pass_filter_measurements.m -nt data/low_pass_filter_measurements.zip ]; then
+    zip data/low_pass_filter_measurements \
+        mat/data_018.mat \
+        mat/data_019.mat \
+        low_pass_filter_measurements.m
+  fi
+#+end_src
+
+The computation files for this section are accessible [[file:data/low_pass_filter_measurements.zip][here]].
+
+** First LPF with a Cut-off frequency of 160Hz
+*** Measurement Description
 *Goal*:
 - Measure the Low Pass Filter Transfer Function
 
@@ -972,14 +999,14 @@ Which makes a cut-off frequency of $f_c = \frac{1}{RC} = 1000 rad/s = 160Hz$.
 #+HEADER: :output-dir figs
 #+begin_src latex :file lpf.pdf :post pdf2svg(file=*this*, ext="png") :exports both
   \begin{tikzpicture}
-    \draw (0,2) node[circ]
-          to [R=\(R\)] ++(2,0)
-          to ++(2,0)  node[circ]
-          ++(-2,0)  node[circ]
-          to [C=\(C\)] ++(0,-2)
-          ++(-2,0) node[circ]
-          to ++(2,0) node[circ]
-          to ++(2,0) node[circ];
+    \draw (0,2)
+          to [R=\(R\)] ++(2,0) node[circ]
+          to ++(2,0)
+          ++(-2,0)
+          to [C=\(C\)] ++(0,-2) node[circ]
+          ++(-2,0)
+          to ++(2,0)
+          to ++(2,0)
   \end{tikzpicture}
 #+end_src
 
@@ -1002,18 +1029,23 @@ Which makes a cut-off frequency of $f_c = \frac{1}{RC} = 1000 rad/s = 160Hz$.
 |      2 | Amplifier 2          |
 |      3 | Time                 |
 
-** Matlab Init                                              :noexport:ignore:
+#+name: fig:lpf_picture
+#+caption: Picture of the low pass filter used
+#+attr_html: :width 500px
+[[file:./img/IMG_20190507_102756.jpg]]
+
+*** Matlab Init                                             :noexport:ignore:
 #+begin_src matlab :exports none :results silent :noweb yes
   <<matlab-init>>
 #+end_src
 
-** Load data
+*** Load data
 We load the data of the z axis of two geophones.
 #+begin_src matlab :results none
   data = load('mat/data_018.mat', 'data'); data = data.data;
 #+end_src
 
-** Transfer function of the LPF
+*** Transfer function of the LPF
 We compute the transfer function from the signal without the LPF to the signal measured with the LPF.
 #+begin_src matlab :results none
   dt = data(2, 3)-data(1, 3);
@@ -1068,16 +1100,82 @@ We obtain the result on figure [[fig:Glpf_bode]].
 #+CAPTION: Bode Diagram of the measured Low Pass filter and the theoritical one
 #+RESULTS: fig:Glpf_bode
 [[file:figs/Glpf_bode.png]]
-** Conclusion
+*** Conclusion
 #+begin_important
   As we want to measure things up to $500Hz$, we chose to change the value of the capacitor to obtain a cut-off frequency of $1kHz$.
 #+end_important
 
-** TODO Low Pass Filter with a cut-off frequency of 1kHz
+** Second LPF with a Cut-off frequency of 1000Hz
+*** Measurement description
 This time, the value are
 \begin{aligned}
   R &= 1k\Omega \\
   C &= 150nF
 \end{aligned}
-
 Which makes a low pass filter with a cut-off frequency of $f_c = 1060Hz$.
+
+*** Load data
+We load the data of the z axis of two geophones.
+#+begin_src matlab :results none
+  data = load('mat/data_019.mat', 'data'); data = data.data;
+#+end_src
+
+*** Transfer function of the LPF
+We compute the transfer function from the signal without the LPF to the signal measured with the LPF.
+#+begin_src matlab :results none
+  dt = data(2, 3)-data(1, 3);
+
+  Fs = 1/dt; % [Hz]
+
+  win = hanning(ceil(10*Fs));
+#+end_src
+
+#+begin_src matlab :results none
+  [Glpf, f] = tfestimate(data(:, 2), data(:, 1), win, [], [], Fs);
+#+end_src
+
+We compare this transfer function with a transfer function corresponding to an ideal first order LPF with a cut-off frequency of $1060Hz$.
+We obtain the result on figure [[fig:Glpf_bode_bis]].
+#+begin_src matlab :results none
+  Gth = 1/(1+s/1060/2/pi);
+#+end_src
+
+#+begin_src matlab :results none
+  figure;
+  ax1 = subplot(2, 1, 1);
+  hold on;
+  plot(f, abs(Glpf));
+  plot(f, abs(squeeze(freqresp(Gth, f, 'Hz'))));
+  hold off;
+  set(gca, 'xscale', 'log'); set(gca, 'yscale', 'log');
+  set(gca, 'XTickLabel',[]);
+  ylabel('Magnitude');
+
+  ax2 = subplot(2, 1, 2);
+  hold on;
+  plot(f, mod(180+180/pi*phase(Glpf), 360)-180);
+  plot(f, 180/pi*unwrap(angle(squeeze(freqresp(Gth, f, 'Hz')))));
+  hold off;
+  set(gca, 'xscale', 'log');
+  ylim([-180, 180]);
+  yticks([-180, -90, 0, 90, 180]);
+  xlabel('Frequency [Hz]'); ylabel('Phase');
+
+  linkaxes([ax1,ax2],'x');
+  xlim([1, 500]);
+#+end_src
+
+#+NAME: fig:Glpf_bode_bis
+#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
+#+begin_src matlab :var filepath="figs/Glpf_bode_bis.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
+  <<plt-matlab>>
+#+end_src
+
+#+NAME: fig:Glpf_bode_bis
+#+CAPTION: Bode Diagram of the measured Low Pass filter and the theoritical one
+#+RESULTS: fig:Glpf_bode_bis
+[[file:figs/Glpf_bode_bis.png]]
+*** Conclusion
+#+begin_important
+  The added LPF has the expected behavior.
+#+end_important

slip-ring-test/low_pass_filter_measurements.m

@@ -0,0 +1,101 @@
+% Matlab Init                                             :noexport:ignore:
+
+clear; close all; clc;
+
+%% Intialize Laplace variable
+s = zpk('s');
+
+%% Initialize ans with org-babel
+ans = 0;
+
+% Load data
+% We load the data of the z axis of two geophones.
+
+data = load('mat/data_018.mat', 'data'); data = data.data;
+
+% Transfer function of the LPF
+% We compute the transfer function from the signal without the LPF to the signal measured with the LPF.
+
+dt = data(2, 3)-data(1, 3);
+
+Fs = 1/dt; % [Hz]
+
+win = hanning(ceil(10*Fs));
+
+[Glpf, f] = tfestimate(data(:, 2), data(:, 1), win, [], [], Fs);
+
+
+
+% We compare this transfer function with a transfer function corresponding to an ideal first order LPF with a cut-off frequency of $1000rad/s$.
+% We obtain the result on figure [[fig:Glpf_bode]].
+
+Gth = 1/(1+s/1000)
+
+figure;
+ax1 = subplot(2, 1, 1);
+hold on;
+plot(f, abs(Glpf));
+plot(f, abs(squeeze(freqresp(Gth, f, 'Hz'))));
+hold off;
+set(gca, 'xscale', 'log'); set(gca, 'yscale', 'log');
+set(gca, 'XTickLabel',[]);
+ylabel('Magnitude');
+
+ax2 = subplot(2, 1, 2);
+hold on;
+plot(f, mod(180+180/pi*phase(Glpf), 360)-180);
+plot(f, 180/pi*unwrap(angle(squeeze(freqresp(Gth, f, 'Hz')))));
+hold off;
+set(gca, 'xscale', 'log');
+ylim([-180, 180]);
+yticks([-180, -90, 0, 90, 180]);
+xlabel('Frequency [Hz]'); ylabel('Phase');
+
+linkaxes([ax1,ax2],'x');
+xlim([1, 500]);
+
+% Load data
+% We load the data of the z axis of two geophones.
+
+data = load('mat/data_019.mat', 'data'); data = data.data;
+
+% Transfer function of the LPF
+% We compute the transfer function from the signal without the LPF to the signal measured with the LPF.
+
+dt = data(2, 3)-data(1, 3);
+
+Fs = 1/dt; % [Hz]
+
+win = hanning(ceil(10*Fs));
+
+[Glpf, f] = tfestimate(data(:, 2), data(:, 1), win, [], [], Fs);
+
+
+
+% We compare this transfer function with a transfer function corresponding to an ideal first order LPF with a cut-off frequency of $1060Hz$.
+% We obtain the result on figure [[fig:Glpf_bode_bis]].
+
+Gth = 1/(1+s/1060/2/pi);
+
+figure;
+ax1 = subplot(2, 1, 1);
+hold on;
+plot(f, abs(Glpf));
+plot(f, abs(squeeze(freqresp(Gth, f, 'Hz'))));
+hold off;
+set(gca, 'xscale', 'log'); set(gca, 'yscale', 'log');
+set(gca, 'XTickLabel',[]);
+ylabel('Magnitude');
+
+ax2 = subplot(2, 1, 2);
+hold on;
+plot(f, mod(180+180/pi*phase(Glpf), 360)-180);
+plot(f, 180/pi*unwrap(angle(squeeze(freqresp(Gth, f, 'Hz')))));
+hold off;
+set(gca, 'xscale', 'log');
+ylim([-180, 180]);
+yticks([-180, -90, 0, 90, 180]);
+xlabel('Frequency [Hz]'); ylabel('Phase');
+
+linkaxes([ax1,ax2],'x');
+xlim([1, 500]);