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PCIe-6351 Analog outputs reference issue

Hello all,

  We are using a PCIe-6351 card for controlling a test stand. Utilizing the AO for motor speed control.

The analog output is a 0-10V going to a ABB 800 series drive. 

All seems fine until another test stand (approx. 10 feet away) is enabled. When this happens we loose a percent of the analog command and it wavers, causing requested speed error. I measured and found that the analog output low (reference) is at ground potential. Measuring from the low pin, I have continuity to the console cabinet. If I unplug the PCI cable from the rear PC card connector, the ground connection opens.

This is causing a ground loop between my 2 testers! I cannot see anything in the manual for isolating the Analog output ground?

Am I missing something here? Would the card really use chassis ground for the analog low reference? Help! Thanks

 

There's never time to do it right, but there's always time to do it over!
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Hi there,

Here are some useful documents we send to customers to help clarify just how the grounding works with our PCIe DAQ cards, as well as provide some useful configurations to help you avoid grounding issues.  This should help you verify that you have the grounding set up correctly between your two test systems and ensuring that you don't introduce ground loops into your measurements.

 

 

Field Wiring and Noise Considerations for Analog Signals

Grounding Considerations - Intermediate Analog Concepts

Isolation Types and Considerations when Taking a Measurement

 

Regards,

 

 

 

 

CC
Applications Engineering
National Instruments
http://www.ni.com/support
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Hello, Thank you for the response.

We have decided to use a Phoenix Contact analog ground isolation module ( Part no: 2864150) between the PCIe and the ABB drive.

Will follow up if that solves our ground loop issue.

There's never time to do it right, but there's always time to do it over!
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