excitation current of 9233 interfacing icp sensor

[LyLee]

I am trying to use crio 9233 module with ICP accelerometers from PCB. However, I noticed there is a noice band around 5-10Hz.  In the user manual of ICP sensors from PCB, it says those sensors need 2-20mA excitation current, and 9233 manual says it provides 2.2mA typical excitation with 2mA minimum. Also, NI modules like SCXI-1531 which is designed to interface with ICP sensors provides 4mA excitation current.  I wonder, could the 2mA current from 9233 be an issue with interfacing with ICP sensors, especially in low-frequency area?

[CharlieM]

LyLee,

First, I don’t have any concerns about the possibility of supplying less than the 2mA to the ICP even at lower frequencies. However I am concerned about the low frequency noise and the integrity of your measurements. Where is that noise coming from (electrical, mechanical)? What frequency range are you trying to measure in?

[LyLee]

Hi Charlie,

The signal I am measuring is of fairly low frequency, <100Hz. But it seems there is a background noise (white-noise like), and the low-frequency part of that noise is messing up the signal.  The problem is, when there is no vibration, the background noise level is very low, but when there is vibration, the background noise level also rises.  It is mechanical signal (of course converted to electrical signal via accelerometer), so it can not be "full-spectrum" white-noise like (the noise has similiar amplitude across the full spectrum). What do you mean "However I am concerned about the low frequency noise and the integrity of your measurements."? Do you have any suggestions? Thanks.

LyLee

[preston_johnson]

Is there a reference such as a tachometer, keyphasor, or other enccoder on the unit under test.  If the vibration you anticipate is synchronous to a reference, it may be possible with the order analysis tools in the Sound and Vibration Measurement suite to filter out the noise.