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FMCG/Operating procedure: Difference between revisions
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# Since we'll be using the Wyllie supplies with the room coils to null the first sensor (Channel 1 recommended, but not necessary), make sure there's a wide output current range on these supplies. Make sure the DC voltage ranges (1) on all three supplies are set to "full" and the output resistors (2) are set to 1 kΩ. This amount of current is generally enough to generate the nulling fields for the room.
# Connect the the two channels of the BK precision function generator to the '''X''' and '''Z''' AC inputs of the Wyllie supply. To start, set them to each output 20 Hz, .1Vpp sine waves. The amplitudes can be adjusted later to suit a the specific situation. The buttons above the BNC ports enable the outputs.
# Reduce the gain on the I-V converter until the output no longer rails. At this point, I've found it easier to go to a "scan" mode on the oscilloscope (time divisions of either 100 or 250 ms). This will allow you to easily see the characteristic dispersive lineshape for the magnetometer.
# Try sweeping the y field and search for the dispersive lineshape.
## If the lineshape is observed, park right in the middle of it.
## If after scanning the entire range of the potentiometer, the lineshape is not observed, try to park the y at the "steepest" point (maximum of dV/dB).
# Enable the output on the BK function generator to apply a field to the '''Z''' coils. If it's not possible to see the magnetometer's response to this transverse signal, increase its amplitude on the function generator. Adjust the DC value of the '''X''' supply and try to reduce the response to the X signal.
# When the response to '''Z''' has been minimized, or if you seem to be unable to reduce the response at all, disable the BK output to '''Z''' and apply a modulation signal to '''X'''. Use the DC Z coils to minimize the magnetometer's response to the '''X''' signal.
# '''Nulling notes'''
## During the above two steps, the DC value of the magnetometer signal will likely swing wildly. Use the '''Y''' current supply to attempt to keep the DC value
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