FMCG/Field nulling and Optimization: Difference between revisions

# 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.

# Try sweeping the y field and search for the dispersive lineshape.

## If the lineshape is observed, park right in the middle of it.

## As you continue to iterate and bring the X and Z fields get closer to their null points, the process will get easier and the wild DC swings associated with adjusting the transverse fields will get smaller (obviously, as the magnetometer is also becoming less sensitive to DC transverse fields). You can probably begin increasing the I-V gain and decreasing the applied field (on the BK fungen).

# Once the optimum '''(X,Y,Z)''' fields are applied, check to see if larger output resistors can be used. Use a DMM to measure the DC voltage on the monitor outputs (white BNC ports). The voltage range on the monitor output is roughly '''-25 V to +25 V''' on each channel. So, for example, if 1 kΩ resistors are being used and the monitor voltage reads 2 V, a switch to the 5 kΩ output resistors is possible as long as the DC voltage is increased to 10 V (maintaining the same current). Larger output resistors have historically given us lower magnetic noise (leading us to believe we are voltage-noise limited on the current supplies).