40mV noiseband on BNC-2110, not on BNC-2090

[Stranman]

I just received a new BNC breakout, BNC-2110, to use with a DAQCard 6036E, but upon hooking it up I'm seeing a 40mV noiseband on a clean signal from a Datel Voltage Calibrator. Upon swapping out the BNC-2110 for a BNC-2090 (keeping everything else in the setup the same) I get results I would expect.  I also tested the 2110 with all unpopulated inputs grounded with no improvement.

Signal is 1V DC sampled at 25 Hz using RSE.  Mean and Std Dev are derrived by a sample size = 100.

BNC-2090 Std Dev = 0.36mV (~16-bit resolution)

BNC-2110 Std Dev = 17.79mV

I already RMA'd the first BNC-2110 thinking it was a hardware problem, but the second one behaved exactly the same way!

Pictures of the outputs are attached.  

Any insight is appreciated.

[Stranman]

and no internal conditioning in the BNC-2090 is used.  Its all set as shipped default.

[ChrisR.]

It looks like you're seeing 120Hz noise, probably from the calibrator ground.  The BNC-2110 doesn't tie the source ground to the DAQ board's ground as hard as the BNC-2090 does.  I suggest either switching to NRSE mode or making that ground connection yourself, for example by somehow connecting the shell of the source BNC to a real board ground, such as AIGND, AOGND, or DGND.  AOGND and DGND are available on other BNCs on the BNC-2110, while AIGND and DGND are both available at the spring terminals.

This is assuming you already have the switches in the "FS" position.  Also, it's possible that the channels that can also be used for analog outputs (AI2-AI7) would have better connections to ground.

Chris