9205 Measurement Variability

[Aaron_K]

Hello,

I am currently setting up a 9205 to do measurements using linear potentiometers  with my compact DAQ system. I'm using a 5v power supply and currently I'm getting about a 50mV variation in my signal. This translates into roughly a 0.010 inch variability in actual displacement. I initially thought I may have a grounding issue, but after playing with the ground configuration, I can't make the signal any better (or worse for that matter).

Does anyone have any thoughts on what I might do next? Or is this just the way things are now? I'm used to our old NI2070 system where the signals were rock solid.

Thanks in advance!

[AwakeTheField · Accepted solution]

Hi Aaron!

A 50mV fluctuation in your 0-5V signal on the NI 9205 is not expected behavior, so there should be some steps you can take to decrease these variations. Looking at the specs for the NI 9205, it shows that the accuracy at full scale (for +/- 5V range) is a little over 3.2mV, meaning that your true value shouldn’t be any different than 3.2mV off of your measured value.

Here are the steps I would take to try to increase the quality of your signal:

• Try using a Differential input configuration for your wiring. I know you said you already checked your grounding configuration, but just to confirm you examined all your options, this “Field Wiring and Noise Considerations” guide has some very good information about some things you may not have tried: http://www.ni.com/white-paper/3344/en/

• Also, check out this article on “Five Tips to Reduce Measurement Noise” as it has some extra tips on reducing noise in your signal: http://www.ni.com/white-paper/3344/en/

• Lastly, if none of those steps seem to help and if you are able to, posting screen shots of your code (particuarlly how your task is configured whether in NI MAX or LabVIEW) and pictures of your physical set-up (the wiring and such), can help myself and others on the forums be able to direct you how to troubleshoot this further.

[Aaron_K]

Thank you for your help. Those articles are very useful and I've saved them. I'm now getting a sub-5millivolt deviation in my signal. Good enough for me.

Thanks again!