SCXI problem with group limit of 16

[klee]

My NI SCXI chassis has four SCXI-1124 modules in it, which supply me with a total of 24 analog output signals.

I currently have Labview configuring the outputs by providing the AO Config VI with the appropriate module/channel number. The AO Config VI then sends the information to the Hardware Config VI, where I specify whether the signal is a voltage or a current before sending it out. This interface is operating perfectly well.

However, because Labview views the SCXI chassis as a single device, I have to specify a group number for each output channel. Since the group number can only range between 0 and 15, I am limited to accessing only 16 channels at a time. Is there any way I can overcome this limitation and access all 24 of my channels?

Thanks,
K. Lee

[sergesl]

Hello Klee,

You do not have to have a group per channel. You can have many channel within the same group for your acquisition. Try just leaving that input unwired.
In addition, I would advise you to use DAQmx instead of traditional DAQ for your program. DAQmx is way easier to program.

[klee]

Serges,

Thank you for your reply. I tried leaving the group ID input unwired for all 24 signals, and as a result none of them worked at all. Is there anything else I can do?

I have passed on the recommendation for DAQmx, but I'm afraid that I am stuck with traditional DAQ for this particular application.

Thanks,
K. Lee

[sergesl]

Hello Klee,

Let me investigate this further and get back with you.

[sergesl]

The AO Config function is only valid for buffered (clocked) analog output operations which aren't supported by the SCXI-1124. The 1124 only supports static (single point) updates. Just use the AO Update Chanels.vi from the traditional palette and give it all 24 virtual channels.

[klee]

Serges,

Thank you very much for your help. The AO Update Channels VI works wonderfully... except that it seems to be applying a gain of 2 before the output. When Labview commands the value x, the NI interface outputs 2x. The strange thing is that when I command x using the "Test" function in the Measurement and Automation Software, the NI interface outputs x. Why is Labview applying a gain of 2 to my output? I can divide all of my signals by 2 before sending them out, but that's not solving the real problem. Any help would be appreciated.

Thank you,
K. Lee

[sergesl]

Hello K.

I will look into that and get back with you.