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PCI-6221: problem with noise

Hi there!


I am owner of NI PCI-6221 device. I have a problem with noise during voltage acquiring.

I’m using SCB-68 terminal board and shielded connection cable.

When I try to acquire voltage from any analog input in differential or RSE configuration I’m acquiring noise with amplitude of approximately 50 microvolts. I’m acquiring this noise even when inputs are grounded (shorted) on AI GND terminals on terminal board.

In attachment you can see example of this noise. It’s a screenshot of LabView project’s front panel. Voltage input settings:

Signal input range: Max: 200m V; Min: -200m V

Terminal configuration: RSE

Clock settings: Samples to read: 100; Rate(Hz): 1k

AI0 channel was grounded on AI GND  terminal.

The same result I have in Measurements and Automation Explorer’s Test Pannels.

What can be the reason of this noise?




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Hi DarkOne,


The noise you are experiencing could be a number of things.  First, please verify that you have the hardware correctly configured when implementing differential or RSE mode.  This document is a great resource for that topic.  Next, what kind of experimental setup are you working with?  Sometimes, noise is introduced from the device's environment.  Thanks!



Applications Engineer

National Instruments

Applications Engineer
National Instruments

Digital Multimeters
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