Can we connect the earth ground on a cDAQ chassis to the ground of a three prong

[Dan86]

What is the best way to ground the chassis on a cDAQ.  Can it be connected directly to the ground on a three prong outlet.  Does NI sell a grounding strap for this application?

[Kurt-P]

Hey Dan86,

The best way to ground the chassis is by using the grounding screw found on the chassis. Here is a great document that that shows where those screws are (figure 8 in particular): 

http://www.ni.com/gettingstarted/setuphardware/dataacquisition/compactdaq.htm

It also gives a little information about grounding. 

Hope this helps,

-KP

[Dan86]

I understand how to connect the ground to the chassis but our lab does not have an earth ground except for the ground on the outlets.  Is it appropriate to run the ground wire to the ground terminal of the outlet?

[Kurt-P · Accepted solution]

Hey Dan86,

No, it is not a good idea to ground the chassis to the wall outlet neutral. This is because the wall ground is not actually earth ground, but are referenced to each other. The neutral is meant to be a saftey measure where current is supposed to flow in case of a short. On page 1-12 saying: 

For EMC compliance, the NI cDAQ-917x chassis must be connected to earth ground through the chassis ground. The wire should be 16 AWG or larger solid copper wire with a maximum length of 1.5 m (5 ft). Attach the wire to the earth ground of the facility’s power system. For more information about earth ground connections, refer to the KnowledgeBase document, Earth Grounding for Test and Measurement Devices, by going to ni.com/info and entering the Info Code earthground.

Here is the link to the manual: 

http://www.ni.com/pdf/manuals/372838c.pdf

And I found the grounding KnowledgeBase they were talking about here:

http://digital.ni.com/public.nsf/allkb/4A441BC4E49541F4862573A000789203

I highly recommend reading through this for the safetly information. It would also be a good idea to talk to some others in the building to see what they use anything for earth ground.