2019-05-16 13:08:27 +02:00
#+TITLE : Measurements On the Slip-Ring
:DRAWER:
#+STARTUP : overview
#+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"/>
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#+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:
We determine if 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 rotation of the Slip-Ring - Noise
:PROPERTIES:
:header-args:matlab+: :tangle matlab/meas_effect_sr.m
:header-args:matlab+: :comments org :mkdirp yes
:END:
<<sec:meas_effect_sr >>
** ZIP file containing the data and matlab files :ignore:
#+begin_src bash :exports none :results none
if [ matlab/meas_effect_sr.m -nt data/meas_effect_sr.zip ]; then
cp matlab/meas_effect_sr.m meas_effect_sr.m;
zip data/meas_effect_sr \
mat/data_001.mat \
mat/data_002.mat \
meas_effect_sr.m;
rm meas_effect_sr.m;
fi
#+end_src
#+begin_note
All the files (data and Matlab scripts) are accessible [[file:data/meas_effect_sr.zip ][here ]].
#+end_note
** Measurement Description
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*** Setup :ignore:
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*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
All the stages are turned OFF except the Slip-Ring.
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*** Goal :ignore:
*Goal* :
The goal is to determine if the signal is altered when the spindle is rotating.
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*** Measurements :ignore:
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*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:
| 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)
<<matlab-dir >>
#+end_src
#+begin_src matlab :exports none :results silent :noweb yes
<<matlab-init >>
#+end_src
** Load data
We load the data of the z axis of two geophones.
#+begin_src matlab :results none
sr_off = load('mat/data_001.mat', 't', 'x1', 'x2');
sr_on = load('mat/data_002.mat', 't', 'x1', 'x2');
#+end_src
** Analysis
Let's first look at the signal produced by the DAC (figure [[fig:random_signal ]]).
#+begin_src matlab :results none
figure;
hold on;
plot(sr_on.t, sr_on.x1);
hold off;
xlabel('Time [s]'); ylabel('Voltage [V]');
xlim([0 10]);
#+end_src
#+NAME : fig:random_signal
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/random_signal.pdf" :var figsize= "wide-normal" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:random_signal
#+CAPTION : Random signal produced by the DAC
#+RESULTS : fig:random_signal
[[file:figs/random_signal.png ]]
We now look at the difference between the signal directly measured by the ADC and the signal that goes through the slip-ring (figure [[fig:slipring_comp_signals ]]).
#+begin_src matlab :results none
figure;
hold on;
plot(sr_on.t, sr_on.x1 - sr_on.x2, 'DisplayName', 'Slip-Ring - $\omega = 1rpm$');
plot(sr_off.t, sr_off.x1 - sr_off.x2,'DisplayName', 'Slip-Ring off');
hold off;
xlabel('Time [s]'); ylabel('Voltage [V]');
xlim([0 10]);
legend('Location', 'northeast');
#+end_src
#+NAME : fig:slipring_comp_signals
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/slipring_comp_signals.pdf" :var figsize= "wide-normal" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:slipring_comp_signals
#+CAPTION : Alteration of the signal when the slip-ring is turning
#+RESULTS : fig:slipring_comp_signals
[[file:figs/slipring_comp_signals.png ]]
#+begin_src matlab :results none
dt = sr_on.t(2) - sr_on.t(1);
Fs = 1/dt; % [Hz]
win = hanning(ceil(1*Fs));
#+end_src
#+begin_src matlab :results none
[pxx_on, f] = pwelch(sr_on.x1 - sr_on.x2, win, [], [], Fs);
[pxx_off, ~] = pwelch(sr_off.x1 - sr_off.x2, win, [], [], Fs);
#+end_src
#+begin_src matlab :results none :exports none
figure;
hold on;
plot(f, sqrt(pxx_on), 'DisplayName', 'Slip-Ring - $\omega = 1rpm$');
plot(f, sqrt(pxx_off),'DisplayName', 'Slip-Ring off');
hold off;
set(gca, 'xscale', 'log'); set(gca, 'yscale', 'log');
xlabel('Frequency [Hz]'); ylabel('PSD $\left[\frac{V}{\sqrt{Hz}}\right]$');
legend('Location', 'northeast');
xlim([1, 500]); ylim([1e-5, 1e-3])
#+end_src
#+NAME : fig:psd_noise
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/psd_noise.pdf" :var figsize= "wide-tall" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:psd_noise
#+CAPTION : ASD of the measured noise
#+RESULTS : fig:psd_noise
[[file:figs/psd_noise.png ]]
** Conclusion
#+begin_note
- 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 using voltage amplifiers - Noise
:PROPERTIES:
:header-args:matlab+: :tangle matlab/meas_slip_ring.m
:header-args:matlab+: :comments org :mkdirp yes
:END:
<<sec:meas_slip_ring >>
** ZIP file containing the data and matlab files :ignore:
#+begin_src bash :exports none :results none
if [ matlab/meas_slip_ring.m -nt data/meas_slip_ring.zip ]; then
cp matlab/meas_slip_ring.m meas_slip_ring.m;
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;
rm meas_slip_ring.m;
fi
#+end_src
#+begin_note
All the files (data and Matlab scripts) are accessible [[file:data/meas_slip_ring.zip ][here ]].
#+end_note
** Measurement Description
*Goal* :
- Determine the noise induced by the slip-ring when turned ON and when rotating
*Setup* :
- 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
Second column: Slip-ring measure
*Measurements* :
| 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
[[file:./img/VID_20190503_160831.gif ]]
#+name : fig:setup_sr_60rpm
#+caption : Slip-Ring rotating at 60rpm
[[file:./img/VID_20190503_161401.gif ]]
** 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
** Load data
We load the data of the z axis of two geophones.
#+begin_src matlab :results none
sr_off = load('mat/data_008.mat', 'data'); sr_off = sr_off.data;
sr_on = load('mat/data_009.mat', 'data'); sr_on = sr_on.data;
sr_6r = load('mat/data_010.mat', 'data'); sr_6r = sr_6r.data;
sr_60r = load('mat/data_011.mat', 'data'); sr_60r = sr_60r.data;
#+end_src
** Time Domain
We plot the time domain data for the direct measurement (figure [[fig:sr_direct_time ]]) and for the signal going through the slip-ring (figure [[fig:sr_slipring_time ]]);
#+begin_src matlab :results none :exports none
figure;
hold on;
plot(sr_60r(:, 3), sr_60r(:, 1), 'DisplayName', '60rpm');
plot(sr_6r(:, 3), sr_6r(:, 1), 'DisplayName', '6rpm');
plot(sr_on(:, 3), sr_on(:, 1), 'DisplayName', 'ON');
plot(sr_off(:, 3), sr_off(:, 1), 'DisplayName', 'OFF');
hold off;
xlabel('Time [s]'); ylabel('Voltage [V]');
legend('Location', 'northeast');
#+end_src
#+NAME : fig:sr_direct_time
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/sr_direct_time.pdf" :var figsize= "wide-normal" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:sr_direct_time
#+CAPTION : Direct measurement
#+RESULTS : fig:sr_direct_time
[[file:figs/sr_direct_time.png ]]
#+begin_src matlab :results none :exports none
figure;
hold on;
plot(sr_60r(:, 3), sr_60r(:, 2), 'DisplayName', '60rpm');
plot(sr_6r(:, 3), sr_6r(:, 2), 'DisplayName', '6rpm');
plot(sr_on(:, 3), sr_on(:, 2), 'DisplayName', 'ON');
plot(sr_off(:, 3), sr_off(:, 2), 'DisplayName', 'OFF');
hold off;
xlabel('Time [s]'); ylabel('Voltage [V]');
legend('Location', 'northeast');
#+end_src
#+NAME : fig:sr_slipring_time
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/sr_slipring_time.pdf" :var figsize= "wide-normal" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:sr_slipring_time
#+CAPTION : Measurement of the signal going through the Slip-Ring
#+RESULTS : fig:sr_slipring_time
[[file:figs/sr_slipring_time.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
[pxdir, f] = pwelch(sr_off(:, 1), win, [], [], Fs);
[pxoff, ~] = pwelch(sr_off(:, 2), win, [], [], Fs);
[pxon, ~] = pwelch(sr_on(:, 2), win, [], [], Fs);
[px6r, ~] = pwelch(sr_6r(:, 2), win, [], [], Fs);
[px60r, ~] = pwelch(sr_60r(:, 2), win, [], [], Fs);
#+end_src
And we plot the ASD of the measured signals (figure [[fig:sr_psd_compare ]]);
#+begin_src matlab :results none
figure;
hold on;
plot(f, sqrt(pxoff), 'DisplayName', 'OFF');
plot(f, sqrt(pxon), 'DisplayName', 'ON');
plot(f, sqrt(px6r), 'DisplayName', '6rpm');
plot(f, sqrt(px60r), 'DisplayName', '60rpm');
plot(f, sqrt(pxdir), 'k-', 'D isplayName', 'Direct');
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_psd_compare
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/sr_psd_compare.pdf" :var figsize= "full-tall" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:sr_psd_compare
#+CAPTION : Comparison of the ASD of the measured signals when the slip-ring is ON, OFF and turning
#+RESULTS : fig:sr_psd_compare
[[file:figs/sr_psd_compare.png ]]
#+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. This saturation could be due to high frequency noise.
#+end_note
** Conclusion
#+begin_important
- The measurements are re-done using an additional low pass filter at the input of the voltage amplifier
#+end_important
* Measure of the noise induced by the Slip-Ring rotation - LPF added
:PROPERTIES:
:header-args:matlab+: :tangle matlab/meas_slip_ring_lpf.m
:header-args:matlab+: :comments org :mkdirp yes
:END:
<<sec:meas_slip_ring_lpf >>
** ZIP file containing the data and matlab files :ignore:
#+begin_src bash :exports none :results none
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_030.mat \
mat/data_031.mat \
mat/data_032.mat \
mat/data_033.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_slip_ring_lpf.zip ][here ]].
#+end_note
** Measurement description
*** Setup :ignore:
*Setup* :
Voltage amplifier:
- 60db
- AC
- 1kHz
Additionnal LPF at 1kHz
*** Goal :ignore:
*Goal* :
*** Measurements :ignore:
*Measurements* :
Three measurements are done:
| Measurement File | Description |
|--------------------+-----------------|
| =mat/data_030.mat= | All off |
| =mat/data_031.mat= | Slip-Ring on |
| =mat/data_032.mat= | Slip-Ring 6rpm |
| =mat/data_033.mat= | Slip-Ring 60rpm |
Each of the measurement =mat= file contains one =data= array with 3 columns:
| Column number | Description |
|---------------+----------------|
| 1 | Direct Measure |
| 2 | Slip-Ring |
| 3 | Time |
** 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
** Load data
We load the data of the z axis of two geophones.
#+begin_src matlab :results none
sr_of = load('mat/data_030.mat', 'data'); sr_of = sr_of.data;
sr_on = load('mat/data_031.mat', 'data'); sr_on = sr_on.data;
sr_6r = load('mat/data_032.mat', 'data'); sr_6r = sr_6r.data;
sr_60 = load('mat/data_033.mat', 'data'); sr_60 = sr_60.data;
#+end_src
** Time Domain
We plot the time domain data for the direct measurement (figure [[fig:sr_direct_1khz_time ]]) and for the signal going through the slip-ring (figure [[fig:sr_slipring_1khz_time ]]);
#+begin_src matlab :results none :exports none
figure;
hold on;
plot(sr_60(:, 3), sr_60(:, 1), 'DisplayName', '60rpm');
plot(sr_6r(:, 3), sr_6r(:, 1), 'DisplayName', '6rpm');
plot(sr_on(:, 3), sr_on(:, 1), 'DisplayName', 'ON');
plot(sr_of(:, 3), sr_of(:, 1), 'DisplayName', 'OFF');
hold off;
xlabel('Time [s]'); ylabel('Voltage [V]');
xlim([0, 100]);
legend('Location', 'northeast');
#+end_src
#+NAME : fig:sr_direct_1khz_time
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/sr_direct_1khz_time.pdf" :var figsize= "wide-normal" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:sr_direct_1khz_time
#+CAPTION : Direct measurement
#+RESULTS : fig:sr_direct_1khz_time
[[file:figs/sr_direct_1khz_time.png ]]
#+begin_src matlab
xlim([0, 0.2]); ylim([-2e-3, 2e-3]);
#+end_src
#+NAME : fig:sr_direct_1khz_time_zoom
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/sr_direct_1khz_time_zoom.pdf" :var figsize= "wide-normal" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:sr_direct_1khz_time_zoom
#+CAPTION : Direct measurement - Zoom
#+RESULTS : fig:sr_direct_1khz_time_zoom
[[file:figs/sr_direct_1khz_time_zoom.png ]]
#+begin_src matlab :results none :exports none
figure;
hold on;
plot(sr_60(:, 3), sr_60(:, 2), 'DisplayName', '60rpm');
plot(sr_6r(:, 3), sr_6r(:, 2), 'DisplayName', '6rpm');
plot(sr_on(:, 3), sr_on(:, 2), 'DisplayName', 'ON');
plot(sr_of(:, 3), sr_of(:, 2), 'DisplayName', 'OFF');
hold off;
xlabel('Time [s]'); ylabel('Voltage [V]');
xlim([0, 100]);
legend('Location', 'northeast');
#+end_src
#+NAME : fig:sr_slipring_1khz_time
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/sr_slipring_1khz_time.pdf" :var figsize= "wide-normal" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:sr_slipring_1khz_time
#+CAPTION : Measurement of the signal going through the Slip-Ring
#+RESULTS : fig:sr_slipring_1khz_time
[[file:figs/sr_slipring_1khz_time.png ]]
** Frequency Domain - Direct Signal
We first compute some parameters that will be used for the PSD computation.
#+begin_src matlab :results none
dt = sr_of(2, 3)-sr_of(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
[px_d_of, f] = pwelch(sr_of(:, 1), win, [], [], Fs);
[px_d_on, ~] = pwelch(sr_on(:, 1), win, [], [], Fs);
[px_d_6r, ~] = pwelch(sr_6r(:, 1), win, [], [], Fs);
[px_d_60, ~] = pwelch(sr_60(:, 1), win, [], [], Fs);
#+end_src
#+begin_src matlab :results none
figure;
hold on;
plot(f, sqrt(px_d_of), 'DisplayName', 'OFF');
plot(f, sqrt(px_d_on), 'DisplayName', 'ON');
plot(f, sqrt(px_d_6r), 'DisplayName', '6rpm');
plot(f, sqrt(px_d_60), 'DisplayName', '60rpm');
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, 5000]);
#+end_src
#+NAME : fig:sr_psd_1khz_direct
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/sr_psd_1khz_direct.pdf" :var figsize= "full-tall" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:sr_psd_1khz_direct
#+CAPTION : Amplitude Spectral Density of the signal going directly to the ADC
#+RESULTS : fig:sr_psd_1khz_direct
[[file:figs/sr_psd_1khz_direct.png ]]
** Frequency Domain - Slip-Ring Signal
#+begin_src matlab :results none
[px_sr_of, f] = pwelch(sr_of(:, 2), win, [], [], Fs);
[px_sr_on, ~] = pwelch(sr_on(:, 2), win, [], [], Fs);
[px_sr_6r, ~] = pwelch(sr_6r(:, 2), win, [], [], Fs);
[px_sr_60, ~] = pwelch(sr_60(:, 2), win, [], [], Fs);
#+end_src
#+begin_src matlab :results none
figure;
hold on;
plot(f, sqrt(px_sr_of), 'DisplayName', 'OFF');
plot(f, sqrt(px_sr_on), 'DisplayName', 'ON');
plot(f, sqrt(px_sr_6r), 'DisplayName', '6rpm');
plot(f, sqrt(px_sr_60), 'DisplayName', '60rpm');
plot(f, sqrt(px_d_of), '-k', 'DisplayName', 'Direct');
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, 5000]);
#+end_src
#+NAME : fig:sr_psd_1khz_slipring
#+HEADER : :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/sr_psd_1khz_slipring.pdf" :var figsize= "full-tall" :post pdf2svg(file=*this*, ext= "png")
<<plt-matlab >>
#+end_src
#+NAME : fig:sr_psd_1khz_slipring
#+CAPTION : Amplitude Spectral Density of the signal going through the slip-ring
#+RESULTS : fig:sr_psd_1khz_slipring
[[file:figs/sr_psd_1khz_slipring.png ]]
** Conclusion
#+begin_important
- We observe peaks at 12Hz and its harmonics for the signal going through the slip-ring when it is turning at 60rpm.
- Apart from that, the noise of the signal is the same when the slip-ring is off/on and turning
- The noise of the signal going through the slip-ring is much higher that the direct signal from the DAC to the ADC
- A peak is obverse at 11.5Hz on the direct signal as soon as the slip-ring is turned ON. Can this be due to high frequency noise and Aliasing? As there is no LPF to filter the noise on the direct signal, this effect could be more visible on the direct signal.
#+end_important
