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FMCG/Data Acquisition with LabVIEW Software: Difference between revisions
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FMCG/Data Acquisition with LabVIEW Software (view source)
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# The '''Response Waveforms''' tab plots the magnetometer responses to the calibration chirps in the top window, and individually the applied (white) and response (color) in the windows below. This is a good way to ensure the calibrations have sufficient signal to noise and that the I-V outputs did not rail during calibration. Again, use the '''NEXT''' button to scroll between channels.
# The '''Response Fits''' tab plots the amplitude and phase response of the magnetometer by Fourier-transforming the data from the previous tab. Note that the data in the '''Y Resp Fit''' sub-tab is in units of '''V/fT''', as it has taken into account the size of the applied field from the '''Calibration''' tab. The raw transformed voltage data can be found in the '''Y raw resp''' sub-tab.
# Under the '''Results''' tab you'll find the data taken during the '''Noise/Heartbeat Sample''' part of the procedure. The top window is the calibrated noise data (in units of fT/rHz), and the bottom window is the raw data collected (in units of V). The cursors in the top window are helpful for determining baseline noise levels. A particularly useful sub-tab is '''All Y or X''' which will display all four channels' worth of PSDs on the same plot for comparison.
# The '''Processing''' tab takes the time series from the '''Results''' tab and calibrates it using the response.
# The '''misc.''' and '''changelog''' tabs are not used on a day-to-day basis.
## Once you are satisfied with the performance of each channel, note all of the modulation amplitudes and demodulation phases. The amplitudes can be copied directly into the main magnetometer program under the '''Modulation Settings''' box. Note again, the modulation frequency applied to all channels is the one in the top (channel 1) box, all others are irrelevant. Unfortunately, the size of the FPGA memory does not allow for independent demodulation phases in the main program, but generally they are all pretty close, so pick an "average" of the values and put it in the '''reference phase''' box below the '''Modulation Settings''' box.
## Click the '''STOP''' button in the '''XY Modulation+Z-mode v1.5.vi''' program. You can leave the program open. '''If you were using the analog outputs from the FPGA box to output the demodulated X signal to the scope, make sure to flip the corresponding Analog Output switches DOWN to reconnect the analog outputs (which will be sending chirp signals now) to the current supplies).'''
# With that, you're ready to take data in Z-mode. To enable z-mode, you need to select the appropriate channels in the '''X Channel Settings''' box on the far left. This will tell the program that both x and y directions must be calibrated before taking a noise measurement. The '''Field Coils''' should be set to '''Printed X - Coil''' and the R(out) will likely be '''5000 Ω'''. By default, the chirp size is '''0.05 V'''. The larger chirp size is to compensate for the fact that the printed X coils have more than a factor of two smaller current-to-field calibration, as well as the fact that in Z-mode, the response to X fields is often smaller than the response to Y fields.▼
==Data Acquisition==
▲#
# Now you're ready to go! Click the '''Run''' button to start the program.
## Again, the first prompt will be one regarding the heaters. Click '''Yes'''.
## You'll first be asked if you want to calibrate the
## Next, the program will prompt you to calibrate the '''OPAMP_X'''. Click '''Yes'''. Flip the '''Chirp''' selector to '''X'''. Click OK and the program will apply the chirp signals to the circuits and monitor their responses.
## Now you'll have to calibrate the magnetometers' responses to the applied Y and X fields. Flip the '''Mag/Mon''' switch down, and follow the prompts, making sure to flip the '''Chirp''' switch to the appropriate position when calibrating each direction.
## Finally, you'll be asked to make a noise or heartbeat measurement. Click '''OK''' and the program will run to completion.
==Data Analysis and Taking More Data===
The program will now analyze the calibration and noise data, but give you ''twice'' as many results as DC-SERF mode! On all of the tabs mentioned above, there are sub-tabs that contain the information about X data that were empty when collecting in DC-SERF mode. You can browse through all tabs (and all channels if you haven't hit '''STOP''' yet!) at your leisure. The '''Results''' tab contains one particularly helpful plot '''Compare Y to X''' which plots the X and Y noise for a particular channel on the same plot for comparison.
Taking more data is the same as in DC-SERF mode. Just select the '''another noise run?''' button, and you're good to go. We have noticed recently that the program often does not behave well when looking at small signals generally associated with "probe" and "electronic" noise runs. We think that has to do with the filtering and are currently investigating.
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