Hi everyone,
Sorry if this is a repeat, I found several threads on how to use COM but seemingly not for my case.
I have 4 resistors wired in series to a constant-current DC power supply. I must measure the voltage difference across each one to calculate its power dissipation, and plan to do this by connecting a differential channel of my NI-9205 across each one. I expect each one to drop 3 V. Therefore the final resistor will reach 12 V, beyond the range of the NI-9205 input channels (+/-10).
My main question is: can I connect the COM pin between the second and third resistors, meaning that my measurement inputs will be -6 to +6 V, rather than 0 to 12 V, relative to COM?
The power supply output can either be floating or grounded, if that makes a difference.
As an additional question to help my understanding: should I see COM as an input, with the 9205 measuring the channels relative to whatever you plug into it, or as an output, clamping a floating circuit to the 9205's existing measurement reference?
Thanks a lot for any help you can all provide!
