The setup: I am trying to use a USB-6218 to measure/log current of between 1 to 10 power supplies, with no more than 4 PS on at a time. PS voltages range from 5V to 35V. Each PS has the negative terminals common and grounded. Each positive leg of the PS has a 100mOhm shunt (this is not ideal as both +/- diff signals are at the high PS potential w.r.t ground). Off of the legs of the shunt is a series 10k. For each channel connected to the NI DAQ, I have a 335k resistor to AI GND on each diff leg.
The problem: Things were looking promising until the 35V supply turned on, once it did the other measurements went wonky. I dug through the specs and noticed a line item that I did not pay much attention to before: AI to AI_GND should be less than 11v, which I assume I am violating and causing the NI device to measure errantly.
Can I get a some concurrence that this will not work the way I want with a 35V supply present? Any workarounds?
