Multifunction DAQ

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DAQ measuring lower voltage than input



We are using the following hardware to read voltage input:


1. NI cDAQ  9171

2. NI 92017 with DSUB.


Four channels ( AI1,AI2,AI3, AI4) are connected to voltage source(4-20mVolts).


We read on the input terminals to the NI 9207 Box (using a digital Voltmeter), the voltage is consistent 4.06 mVolts.

However, on the NI - Measurement and Automation Explorer the voltage drops to 3.35 mVolts.


Do we need to correct anything in the setup for the offset in voltage?


Configuration of our setup:



Thank you for your help.


Best Regards,


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Message 1 of 6

The 9207 has eight channels that can directly measure 20 mA current signals. Why not use these channels instead of measuring the voltage difference on an additional 100 Ohm resistor?


Regards, Jens

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Message 2 of 6

It might be worth it to review Table 1 of the following:


This will ensure you have a properly wired measurement setup with proper terminal configurations. Also, if you want to measure current use the current inputs as another user mentioned.  

Applications Engineering
National Instruments
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Message 3 of 6

Hi Jens,


Thanks for your input.


Our environment is set in a way where we want to capture the voltage input.

We would want to use the voltage for our further calculations and then compare the result with the old setup.



Best Regards,


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Message 4 of 6

Hi CH,


The document was helpful.


What we did try and it resolved the issue:

Short the Common with the negative terminal of the signal.


I have a quick question with respect to the COM channels.

Since, we will be having 4 independent inputs do we connect all negative leads of the inputs to the independent 4 COM channels.




Thank you.

Best Regards,


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Message 5 of 6

It will be the same ground, but yes I would use thee 4 channels instead of just a single COM channel if possible.

Applications Engineering
National Instruments
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Message 6 of 6