USB-6009 Voltage Accuracy Problem

[perk_bud]

Hi friends


I'm using the NI USB-6009 for measuring analog input voltage but there seem's to be a difference in the reading's shown by the test panel and the one shown by the voltmeter.The difference seem's to about 1.5 volt's.Is this normal or what is the getaround for this problem.


                                                                                                                                                                                 Thank you.

[Hani R]

Hi Perk_Bud,

There are a few things you can try to narrow down the source of the problem.  Please provide the following details so that we can help you further:

Is the signal you are trying to measure a DC signal?
Does the voltage difference (between the USB-6009 and the voltmeter) remain fairly constant at 1.5V or does it fluctuate over time? 
Are you measuring a differential signal, referenced single ended signal, or a non-referenced single ended signal?
Is the source of your signal grounded to earth ground or is it a floating source?

Try to connect an analog output channel from the USB-6009 back into an analog input channel.  Output a constant voltage and check if it the analog input channel is reading the correct voltage.  If it is not correct, then try a different input channel.  If it is correct, then you might have a problem with grounding.  Refer to the DeveloperZone article: Field Wiring and Noise Considerations for Analog Signals for details on how to properly ground your signal.