Laptop charger affecting signal

[zgeorge30]

I'm using a NI USB-6216 DAQ and my signal from my load cell kept cutting out when I connected it to a laptop. When I unplugged the power cord everything works fine. See the results below:

• Top graph: disconnected the power cord.
• Middle graph: fully charged, power connected. (this is what it was doing previously)
• Bottom graph: 65% battery with power connected. (cut-offs are not as frequent)

[zgeorge30]

[zgeorge30]

any suggestions to fix this so it stops cutting out with the power connected will be appreciated!

[bstreiff]

How do you have your load cell wired to the USB-6216? What input configuration are you using (differential, RSE, NRSE)?

Also, what do you have AI GND wired to?

[SnowMule]

Sounds like a ground loop somewhere.  Isolate your power supplies.

Some engineers like to cut the ground pin off a power cable they use with their benchtop instruments to eliminate ground loops through the instrument... I don't like doing this, usually there's a reason the signal's noisy.

[zgeorge30]

It's wired into a load meter and the analog output from the load meter is wired into the DAQ. I was using differential but after reading your post, i tried it in RSE. This eliminated the cutting out of the signal but still has considerable noise.

[Julianne_K · Accepted solution]

Hi zgeorge30, 

I would recommend that you read this document for more information on how to wire your system, and for the diferences between differential, RSE and NRSE configurations. Please let me know if you still have questions. Sincerely,