NRSE Measurement with 60hz noise

[TitanLabview]

Thanks in advance for any help on this problem.

I am measuring an analog voltage and from what I had read in the field wiring white paper (https://www.ni.com/en/shop/data-acquisition/measurement-fundamentals/field-wiring-and-noise-consider... it looks like I should be using NRSE to measure my grounded signal source.  However, when using NRSE I am getting a major 60Hz component. (See attached screenshot)  However, when I connect AI Sense to AI GND, the signal is fine (this also happens if I touch my oscope ground to the device ground).  The signal I am measuring has its GND connected through a single ground plane to the power supply ground, which is connected to the same powerstrip as the computer I am running the DAQ card with.  It is a grounding problem, but I can't for the life of me pinpoint it (maybe that has to do with it being a Friday afternoon).

[Esteban.R]

Hi Wbren

Take a look to this links they might help you with your issue. It seems that you have a ghosting problem how many channels are you using? Only one?

How Do I Eliminate Ghosting From My Measurements?

Troubleshooting Unexpected Voltages, Floating, or Crosstalk on Analog Input Channels

Regards

Esteban R.

[TitanLabview]

The same waveform will occurr whether I am measuring multiple channels or single channels.  I had ghosting problems before with this device, so we created a signal buffer and that solved the ghosting problem so I am quite confident it is not a ghosting issue.  Thanks for the response though, it is always good to go through all the usual suspects!

[Esteban.R]

Hi Wbren

Which Hardware and devices are you using?

Are you using a PCI card?

What kind of signal are you trying to measure? Is the signal from a signal generator? Have your try another to measure the signal with another channel or device in order to determine if the signal is generated correctly?

Are you sure that your external device is grounded signal source? Have you checked the manual and specifications?

If you are shorting AI sense to AI GND then you are doing something for a non referenced source and you say that the device is grounded signal to source

When you say that you connect AI sense to AI GND you mean that you are connecting both terminals using a resistor like in the white paper that you are referring? (Section Measuring Floating (Nonreferenced) Sources)

Field Wiring and Noise Considerations for Analog Signals

Regards 

Esteban R.