Analog Input Channel Numbering (PXI-6224)

[shardy1216]

Hello,

I have a PXI-6224 I/O module, and I have 10 analog voltages that I need to measure with the 6224.  The voltages are differential pairs, so, I have them wired up as I am supposed to:
{(ai0,ai8) ; (ai1, ai9) ; ... ; (ai18,ai26)}.  I am writing the code in C, and declare the voltage measurement task as :

DAQmxErrChk(DAQmxCreateAIVoltageChan(taskHandleReadAnalog[i], portNameReadAnalog[i], "", 10106 , minval[i], maxval[i], DAQmx_Val_Volts, NULL));

My question is, what do I put for the physical channel (portNameReadAnalog[i] in the above line) for a differential configuration (i.e. if I put /PXI1Slot2/ai0) does it know to read the difference btwn ai0 and ai8)?   Basically, my question is, how do I refer to the differential channel pairs?  By the ai number of the V+ line (0,1,2,3,4,5,6,7,16,17,18,19,20,21,22,23)?  Or is there another way to refer to them?

Thanks.

[MickeyD]

Hello,

Your natural instinct was correct.  You should only put the V+ channel into the physical channel parameters.  You can find documentation on this in the DAQmx C Reference Help; in the section describing M series boards under device specific considerations.  I would advice you to use a channel list Dev0/ai3:6  would be positive channels three through six and their negative input counterparts.  Please let me know if you have any further questions on this issue, so that I can stay on top of your issue.

Thank you,

Michael

Message Edited by Mike_D on 11-06-2006 03:59 PM