how do you say inputChan[] = "/Dev1/ai0:7,Dev1/ai16:23,/Dev1/ai32:" in LV 8.51

[asquit]

Folks -

PCI-6225 DAQ board with one scb, one scc term block. Have been running in a Mac G5 with c routines, but now need to move the DAQ board to an XP box and use LV 8.5.1.  need to start a task for 2500 samples on 17 differential channels, and would prefer to use the DAQmx vis (I think)to change sample count etc programmatically, rather than set tasks in MAX or in express vis.  Sample clock timing, triggers, etc are all straightforward c to vis but I don't get the string formatting in e.g. DAQCreateVirtualChannel.vi.

thanks

Alex

[aNIta B]

Hey Alex,

         You'll want to either make a control or indicator into the channel input of your DAQmxCreateVirtualChannel.vi and your syntax will be: Dev1/ai0:7,Dev1/ai16:23,Dev1/ai32 -so pretty much like you had it.  LabVIEW does a pretty good job at not letting you enter improper syntax, and should populate your available channels and devices automatically.  Happy programming!

[asquit]

aNitaB -

Here's my modified  ACQ&Graph Voltage Int Clk -Dig Trig.vi with a few mods :

1.) I named my board "6225-pci" in MAX.

2.) Eight diff channels in. 

3.)  clock + trig as the old hardware (when it was running on mac in c).

I can see 16 channels, but not 8 combined differentially.  Help ?

thanks 

[Dennis_Knutson · Accepted solution]

Why would you expect to see 8 channels when you have 16 defined in the physical channel list? I don't think you understand at all how the channels are used in differential mode. Ai0 is paired with ai8, ai1 is paried with ai9, etc. By specifying differential mode and ai0, ai8 is automatically used. You DO NOT specify the - inputs in differential mode and you CANNOT pair ai0 with ai16. If you were using differential mode in traditional DAQ or in a different language, nothing is different with LabVIEW.

Message Edited by Dennis Knutson on 04-06-2009 10:03 AM

[asquit]

(banging head on desk) . Looks like I have a new hardware problem. I had not been seeing signals I had expected, and assumed that the problem was the channel assignment syntax, which was actually working.  As soon as I tried index array on the waveforms back from the read vi  ( after you pointed out the bonehaead nature of the question) , all became clear.

thanks for pointing that out.

Alex