No physical devices found in NI-DAQmx using a PXI-6229

[Dr Hfuhruhurr]

I'm new to PXI systems. I'm trying to set up a global virtual channel in Measurement and Automation Explorer wersion 4.1.0. I have a SCB-68 attached to a PXI-6229 in a PXI-1042 chasis controlled by a laptop connected via a CardBus-8310 to PXI Expansion Kit. I have NI-DAQmx version 8.0.1 installed. I'd like to connect an LVDT to the SCB-68 and create a global virtual channel for the LVDT. When I try to do so it says there are no supported devices found. I've used SCXI sytems before but not PXI so I may be going about this wrong. Thanks in advance for any help.

[garretth]

Hello,

Actually it sounds like you are doing everything right. The only issue is that the DAQmx driver will not allow you to create an LVDT channel unless you have specific LVDT hardware connected. For example, if you simulated the SCXI-1540 then you would be able to create an LVDT virtual channel. The best thing to do will be to just create a voltage channel and then apply an appropriate custom scale to convert from voltage to position. You will also need to provide your own excitation for the the LVDT.

Cheers,

[Dr Hfuhruhurr]

This makes sense except my LVDT has a + signal, - signal and ground. This results in two different voltage channels. Can I create a virtual channel that is a subtraction of these two channels? Or is there some other way to do this as a task?

Thanks,
Mark

[garretth]

You cannot create a task to encompass the two channels as one. You will have to just perform this calculation in software. However, there are also LVDT to DC converters that you can use as signal conditioning before connecting to your DAQ card. The only LVDT signal conditioning that National Instruments has is in the SCXI platform.

http://digital.ni.com/public.nsf/websearch/BEE5506E0358E82186256B9200701ECA?OpenDocument

[Dr Hfuhruhurr]

I'll try to use software to do this. Thanks for the info.

Mark