Output with no Input?

[DL84]

Hi all,

I'm new to the DAQ world, most of my LV experience is with controls.  I've been working on a program and i'm getting some strange results.

Attached is a plot of an output from DAQ assistant polling 3 channels simultaneously from a USB-9233:

I'm trying to get vibration levels but it seems, with or without the BNC cables hooked up there's always 1 channel that seems to have a signal (even a small one but its a whole factor of 10 off from the rest)

Any idea whats going on?  The attached picture is with nothing attached to the DAQ, its just plugged in and reading unconnected terminals (which should show very close to zero)

[DL84]

Oops it was the sensitivity setting in the DAQ Assistant - now I'm not sure where it should be set...by default its 1000, but on the sensor I have it has a certificate of calibration that lists sensitivity as 106.8mV/g.....which ones goes in that box?  If its the 1000 then how do you take the 106.8mV/g scaling factor into account?

thanks for the help!

[dsb@NI]

A sensitivity of 1000 mV / g applies no scaling to the acquired data. Definitely replace 1000 by your known sensor sensitivity. You should also periodically calbrate your accelerometer to verify that it is performing according to specifications. In fact, if you have a calibrator, there are LabVIEW VIs (software functions) in the Sound and Vibration Toolkit that will measure the calibrated sensor sensitivity. Use the calibrated sensor sensitivity to ensure that you are accurately scaling the data to engineering units.