I have a U6 that's a few years old. I am measuring the differential voltage across two wheatstone bridge (strain gauge application). The left leg of bridge A is connected to AIN0 and the left leg of bridge B is connected to AIN2. The right leg of bridge A is connected to AIN1 and the right leg of bridge B is connected to AIN 3.
I modified streamTest.py to use differential and a gain of 10 for AIN0 and AIN2. The DMM measures the same as the output for each bridge but the gain has no effect on the output, as if the gain is 1 regardless of the channel options, 128 (x1), 144 (x10).
Is something wrong with the U6 preamp or am I misinterpreting how the gain works?
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Gain will change the voltage range which is approximately +/-10V divided by Gain. The ChannelOptions for StreamConfig are documented here included associated gain to voltage range:
https://labjack.com/support/datasheets/u6/low-level-function-reference/s...
For ChannelOptions, 128 (b10000000) is differential with gain x1, which is a +10.1 to -10.6 V range. 144 (b10010000) is differential with gain x10, which is a +1.01 to -1.06 V range.
If the differential voltage on AIN0 and AIN1 are between +1.01 to -1.06 V, voltage readings will be similar with a gain of x1 and x10.