Odd Signal from USB-9215?

[Bocchini]

I'm having trouble setting up and LVDT to my USB-9215. The voltage that my daq bored is reading goes from a little over 5 V to 3.3ish V  at regular intervals (see attached screenshot). I've measure the output of the LVDT with a voltmeter and it stays constant at the 5 V reading. I don't understand why it keeps dropping to 3.3 V. If anyone has any insight it would be appreciated.

[KyleTTU]

Hi Bocchini,

Does this happen only when reading your LVDT?  Can you apply a battery to the same terminal and read a constant voltage?  

Regards, 

Kyle S

[Seth_B.]

From the look of your settings, those drops are occuring for less than 17 milliseconds.  It's very unlikely that a voltmeter will pick up that kind of fluctuation.  You'll need a decently fast oscilloscope or something to read that kind of drop.

[Bocchini]

I've checked both the DAQ and the LVDT signal conditioning box inedependently and both seem to work. I called LVDT manufacturer and was told that the DAQ bored might not be completely compatible with the LVDT signal conditioner... Something about impedence differences. I'm waiting to hear back but if you know of a way to correct this problem it would be helpful.

[Meadow]

Hello,

This topic is a duplicate from link below:

http://forums.ni.com/t5/Signal-Conditioning/Need-help-with-LVDT-setup-on-USB-9215/m-p/1602154#M6097

[Bocchini]

Meadow,

I've checked the calibration and it matches what it should be. High output corresponding to +5.0 V with a read out of .2 inches, and low output of -5.0 V with a read out of -.2 inches. Both devices work independently of one another so it seems that the problem lies within the coupling of the two, perhaps caused by impedance differences, however I'm really not sure how to go about correcting this issue.