5 differential inputs and 4 single ended with SCB-68

[JJC]

i am a little confused about how i need to wire this and how to aquire the signal. i am trying to take 5 differential inputs and 4 single ended with the SCB-68. i have gotten the differential inputs to work, but am i having problems with the single ended ones. they are all from accelerometers, with a voltage out for each axis. i can wire it to take the differential between each signal and the ground, but i would think there is a better way. i thought i would be able to wire each led to a terminal and then the ground to the "ground" terminal, but i cannot get the daq to read it this way in my vi. can anyone help me? thanks

[devchander]

Hi JJC,

Sorry to say that You cannot connect signals like that!

You cannot have both differential and single ended connection modes at the same instant on a single DAQ card.

Either  have all AI channels SE or all AI channels in Diffferential mode

Just curious, which DAQ card are you using?

Hope this helps

Regards

Dev

[WM_John_Weeks]

Wait, Dev, with NI-DAQmx and M-series devices you can mix differential and RSE connections. I agree we need to know more about the hardware involved. The SCB-68 is mostly irrelevant to the answer.

With the right hardware, he can connect the 5 differential inputs this way:

AI0-AI8
AI1-AI9
AI2-AI10
AI3-AI11
AI4-AI12

And the 4 RSE channels this way:

AI5-GND
AI6-GND
AI7-GND
AI13-GND

There is no way to have the RSE channels in a single contiguous block of channels. And, using NI-DAQmx he will have to use separate calls the DAQmxCreateAIVoltageChan to add the differential channels and the RSE channels.

[WM_John_Weeks]

I should mention that my reply reflects the fact that I write in C++ using VC++.net. I know that Labview has access to exactly what I was talking about, and it uses very nearly (if not exactly) the same names.

[Dennis_Knutson]

John's correct. With both DAQmx and traditional DAQ, you can mix input terminal configurations in a single read and an M series board is not required either. As long as the board supports differential and RSE and there are enough channels available, there should be no problem.

[JJC]

i am using the DAQ PCI 6254 card. this is how i thought it could be done, but i couldnt get it to work. can some one send me a vi with this set up in DAQmx? thanks.

[devchander]

John and Dennis,

Thank you for correcting me!

regards

Dev

[Dennis_Knutson]

Try something like this.

Message Edited by Dennis Knutson on 03-03-2006 08:33 AM

[WM_John_Weeks]

>Thank you for correcting me!

It's a pleasure 🙂 With you, we don't get many chances!