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FMCG/Operating procedure: Difference between revisions
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→Field Nulling
ElenaZhivun (talk | contribs) |
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The process of nulling the fields is somewhat difficult to explain in words, but gets easier with practice. The procedure below is not to be followed word-for-word, but can hopefully be useful as a guide.
[[File:WyllieSupply.jpg|thumb|Board layout of a single-channel Wyllie current supply. The labeled parts are as follows (for the red switches, the switch pushed "up" is enabled, "down" is disabled):
1. DC input attenuator: [divide by 10, no attenuation, divide by 100] 2. Output resistor: [50 Ohm, 500 Ohm, 1 kOhm, 5 kOhm] 3. Output current: connects to cat5 port at rear: 4. Voltage monitor: Measures the output voltage across *both* output resistors. Hence the output current is this voltage over twice the output resistor value. 5. AC input attenuator. Can be shorted or controlled by a switch [no attenuation, divide by 10, divide by 100] 6. DC potentiometer control input (from front panel) 7. AC input (from front panel) 8. Power input]]
# 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.
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