Loop Ground and Insulation between channel and ground

[brunolorenzo]

Hey guys,

I have a problem acquiring the signal from two different accelerometer sensors, where channel 1 is influencing the voltage read from channel 2, either in Differential mode or in RSE mode. I don't know if the problem could be caused by the ground loop or the isolation of the DAQ channels. I will be leaving the diagram of the connections made.

Bruno Lorenzo

[crossrulz]

What accelerometers and DAQ are you using?

[brunolorenzo]

ADXL203 and NI6218

[crossrulz · Accepted solution]

1. You should be using Referenced Single Ended configuration for the DAQ channels.  AI_GND should be tied to the device's ground.

2. Following this circuit note (CN0189), it looks like you should add some amplifiers between the accelerometer and the DAQ.  I didn't dive into the circuit, but you may get away with simple voltage follower op-amp setups.  This was my first thought with your first post as ghosting is common with high output impedance devices.  Adding simple op-amp circuits usually fixes that as op-amps have very low output impedance.

[brunolorenzo]

Thanks, just adding the voltage follower helped.👍

B. Lorenzo