Rif.: ni 4340 lvdt modul for PXI, wrong data while zero crossing

[elhanan]

Hello all,

I am using a pxi systems (2 different systemes) , with a LVDT (4 wire) +/-1.25mm, +/-20mm +/-40mm.

When lvdt moves from one direction to another, close to 0 mm, there is a jump in the reading.
It is not the same jump (in mm) for a different LVDT.
The jump (delta) is about 0.2-1.5mm, from plus to minus or vice versa (regardless of direction).

Any idea?

Thanks
Elhanan

[santo_13]

The question is whether is your LVDT behavior is causing the jump or an instrument problem. Were you able to verify that your LVDT sensor is working correctly?

[FrancescoM12]

Dear Elhanan,

i've the same behaviour on my PXI 4340, did you find the solution?

If i change the excitation frequency the jump seems to be less.

All your experience on this problem can be very important for me.

Thanks in advance.

[elhanan]

I didn't find solution to this behavior.

I will try changing frequency.

Elhanan 

[FrancescoM12]

Dear Elhanan,

I probably found the solution of the zero crossing problem.

In my opinion is a grounding issue, connecting the B lower side of the LVDT to GND/CASE the board is reading better around the zero position.

Let me know if is working for you.

Thanks, have a nice day.