DAQ Channel Shift

[Keith Brainard]

I have an application where I read a text file and dynamically create DAQmx scales and create channels into tasks by type (AI, AO, DI, DO). This has been working fine for a while, several months at least. Today I found that all of a sudden, all my channels were reading the next channel.

Imagine ten temperatures across two SCXI modules, and suddenly each channel starts to read the next channel's value. TC1 starts reading what TC2 had been, TC2 starts reading what TC3 had been and so on. Even across modules - SC1Mod1/ai7 started to read the value that should have come in on SC1Mod2/ai0! This only affected analog inputs.

An example: With a signal source set to 20 mA, plugged into SC1Mod6/ai5, the full scale reading was reading on the channel that is supposed to be on SC1Mod6/ai4, according to scaling for ai4. Stopping the app, and restarting it (which stops, clears, and re-creates the DAQmx tasks) "fixed" the problem, and now ai5 shows its full scale value.

What could cause this? DAQ driver? MAX? SCXI Chassis? DAQ Card?

LabVIEW 7.1

MAX 4.3

DAQmx 8.6

PCI-MIO-16XE-10

SCXI-1120D, SCXI-1120

Thanks

[xtal]

I've seen the same thing, channels switching in the middle of a run, with an SCXI system I use here occasionally. I never did figure out what the problem was because it was so intermittent and unreproducible. I am using LabVIEW 8.2 and the SCXI-1600 with 2 or 3 SCXI-1112 modules.