Multifunction DAQ

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USB-6210 multi-channel acquisition in NRSE mode

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I am trying to measure voltage at multiple points in a circuit using the USB6210 DAQ. I am using a function generator to input a voltage to the circuit and the circuit itself is referenced to the FGENs ground (which in turn is the wall ground). I have configured the DAQ to work in the NRSE mode. The FGEN ground is connected to AISENSE and AIGND. AI0-AI15 are connected at different points on the circuit (basically a resistor network) where I want to measure voltage. According to the datasheet this connection should work


However, if I physically unplug AI2-AI15 and read data from the DAQ all channels show pretty much the same reading as can be seen in the image. The labview code is a modified version of the example analog input code.  Only the channel settings was changed

 

mjohn616_0-1594230339950.png

 

mjohn616_1-1594230399437.png

 

Can somebody help? Is it recommend to have a sort of pull down resistor or something between the measuring channels and AI ground? 

 

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I normally use differential in like situations with good results and use bias resistors about 47K from both inputs to gnd.

 

 

 
 

 

 

 

 

 

 

 

 

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Ah! I didn't come across that when I was looking through the support documents. Adding a bias resistor makes sense to me. I want to try it in the NRSE instead of the differential mode because I need to monitor from all 16 channels (single-ended)

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Yeah! I can't find the original document I had run across years ago, which gave details, but this is the jist of it. Good luck!

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