NI 9205 I/O daq

[HollyandIvy]

I'm using 4 DIFF mode Ni9205 channels. When I was doing test with voltge generator, I only wires input to channel 1( AI0,AI8) and channel 4(AI4 and AI12), however the data I loggered shows a weired problem. Both channel 2 and Channel 3 showed the same profile as Channel 1 signal, only channel 4 is different because I applied different voltage to it. The loggered magnitude seemed fine, only those two channels between 1 and 4 gave values which should not be.

[Rhys - AE]

Hi there,

  A few questions that may help us help you:

  I assume you’re using the C-series module? Not the Wi-Fi or Ethernet modules?

  If you are using a C-series, is it in a cDAQ or cRIO?

  Are you seeing the incorrect results in LabVIEW or MAX test panels? Or even Signal Express?

  If you are seeing the results in LabVIEW, can you post up your code so I can try to recreate your scenario in the lab.

Here are just a few ideas just to get you started:

  Double check your wiring, have you correctly grounded the module? (This is one of the most common mistakes the causes ghosting across channels)

  For pin-outs of the module here is the manual for the C-series module: http://www.ni.com/pdf/manuals/374188d.pdf

  Is your code pointing to the correct channel?

Look forward to hearing back,

[HollyandIvy]

Yes, I'm using cRIO, and the result is read from Labview. I think it may be the floating problem as you say incorrect grounded.  I can't find the instruction for module fround in the manuals but simply input pins.

[Rhys - AE · Accepted solution]

Hello again.

I've had a look into this and it would seem that ghosting is the issue. As a quick fix you can wire any unused channels to ground. The ground pin is labeled "COM" (for common) and is pin 17.

I think you are only seeing the ghosted signals because you are running a test, in which the 9205 is trying to scan every channel. Once you start working with real inputs and reasonable sized voltages the 9205 should be able to determined between connected channels and un-connected channels, and read only the connected channels.

If the problem persists, I recommend you have a look at this article:

http://digital.ni.com/public.nsf/allkb/B9BCDFD960C06B9186256A37007490CD

I hope this has helped, best of luck with your application!

[HollyandIvy]

Yes,thank you. U think mine is Unconnected or Open Channels problems, I'll fix it.