USB-6009 AI Drifting...

[Thor]

I'm measuring a strain gauge through an amplifier (AI0 is connected to the output of an AMP04F instrumentation amplifier), but I've seen this problem when

   1. Using the USB 5V for Vstim, and reading the strain gauge on AI0/AI4

   2. Reading USB 5V (from the USB-6009).

I'm running the DAQ at 40KHz (I want 20 samples/sec, and I do an average of 2000 samples for each reading).

If I put the DAQ in a For loop (say for 40 seconds), the last dataset is lower than the first dataset.  After 60 seconds, it seems to have stabilized...

I'm trying to use this to run a stepper setup (FlexMotion PCI card and NuDrive), but I cal at 0 (slope/offset), but when I start moving, etc (~240 sec to get into position), I'm off by 50/60 grams (2Kg cal weight = 5+.319 V).

If I change the DAQ clock speed, the offset changes; if I cal at 40KHz, I have to run @ 40 KHz...

All this doesn't seem right... what's going on?

Thanks,

Thor Johnson

[Elijah_K]

Are you using the DAQ Assistant for your application?  I would recommend that you try using one of the example programs that ships in the LabVIEW Example Finder.  Additionally, I wouldn't recommend driving the amplifier from the 5V on the 6009 because it cannot source very much current and may cause unexpected performance.  I recommend using an external power supply instead.