DAQ Grounding

[sous]

I am having trouble with one of my AI voltage signals, i found when i connect my charge amplifier from my pressure transducer it imposes a 500mV noise signal on all the AI nodes of my device. I am using a NI USB 6351 and wondered if there is a way to ground the device? If there is not I am open to other recommendations.

[santo_13]

Please share more details of your charge amplifier, how it is powered, how it is connected with the DAQ etc.

Check out this article - https://www.ni.com/en/shop/data-acquisition/measurement-fundamentals/analog-fundamentals/grounding-c...

[sous]

The charge amplifier I am using is a Kiag Swiss Type 5001, it is connected to the daq with a BNC cable, the one side is cut off and the wires that feed into the DAQ are soldered onto the live and shielding of the bnc cable. The DAQ is powered by it's own wall outlet and all other devices are powered by another wall outlet. I disconnected everything one by one to determine which produces the noise. The noise only appears when the charge amp revoices power and when disconnected the noise continues until all charge has left the charge amp.

[Henrik_Volkers]

Oh, a Kistler 5001  .. 🙂  

That thing is how many years old?  50?   (First versions are build in the 50s of the last century 😉 )

First versions have no connection to PE via power connector and are floating, with some capacitive coupling to the line...

(and I have in mind that they do not comply actual isolation regulations...   but didn't found a source for that.... )

A common failure:  the line filter and powersupply capacitors are dried (if not leaky)  ... resulting in hum.

However that doesn't match your test

The noise only appears when the charge amp revoices power and when disconnected the noise continues until all charge has left the charge amp.

Have you tried differential input? and maybe add a 1M Ohm resistor from 5001 BNC out shield to 6351 AGND next to Ax- input