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What channel configuration should I use: pseudodifferential?

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I have three signal terminals; a common ground, a V0 and a V1, with both V0 and V1 measured relative to the common ground terminal.  There is some environmental noise contamination, so I can't ignore the common ground and just wire V0 as the center wire and V1 as the "ground"...I need the ground wire for shielding.

 

I want to measure V1-V0.  I am writing a custom app in C#.  It is important to keep the readings as low-noise as possible, and keep the computations as simple as possible (I know, use C++ not C#, not my choice).

 

I think my best option is to set up A0 to read V0, and A1 to read V1, both as pseudodifferential signals, and then in my code find V1-V0.  Is that correct? I read the post on terminal configuation on NI's website, but I just want to make sure.

 

Things perhaps pertaining to the question, but maybe not: 

I am using a USB-9234 DAQ.

I don't require sensor excitation.

V0 and V1 are bandlimited to 10Hz - 1kHz with low noise analog filters (to under 50uV), and the signal of interest is bandlimited to 65Hz-120Hz.  Max voltage from V0-gnd, V1-gnd, and V1-V0 are all +/-5V.

Signals are low impedance (~10ohms).

 

Thanks for your thoughts!

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Accepted by topic author jcsquire

Hey jcsquire!

 

You are correct in using a pseudodifferential input setup if you wish to reduce your noise.  Pseudodifferential is great at minimizing ground loops which lead to more accurate measurements.  With using this setup I believe you would have to measure both independently and then subtract them out afterwards to maintain your sheilding with the ground line.

 

In summary, sounds like you know what you're doing.

Field Wiring Diagram

Pseudodifferential Input

Doug Farrell
Solutions Marketing - Automotive
National Instruments

National Instruments Automotive Solutions
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