random errors using SCXI analog input on SCXI1100

[abartleson]

This system is using a AT-MIO16E card and labview. I am performing single channel analog scans using the NI SCXI analog input example, modified to use the RMS and extract frequency examples. During static testing (ANy one input), the readings are fine. In one frame, the 1125 is polled 4x, and the 1100 is polled once. The scan for the 1100 module does an RMS and frequency extraction. In this frame, the result from the frequency is NAN and the RMS is 0 about 50% of the time. Individually, the modules acquire the data flawlessly (1 volt, 49.5kHz). The 1100 is is passed scan rate, buffers, scans. The signal acquired is a 50kHz square wave. I've tried scan rates from 150 to 250k. Any ideas on what could be causing this?

[Filipe A.]

Hello;

It's hard to tell what might be happening without seeing the code, but the best way to test that out is to acquire the data without applying the RMS functionality, and double check if the data is the expected.

If it is, then the problem is inside the RMS function. I'm sorry I couldn't give you a definite answer, but at this point the problem might be anywhere in the code, and we probably need to narrow the possibilities down.

Regards
Filipe A.
Applications Engineer
National Instruments

[abartleson]

Felipe,

Thanks for the reply.

The AI "read waveform" sometimes passes a blank output array. While the VI is running, it's passing valid data. Conversely, the "read scaled array" AI always passes valid data.

Any idea on what could cause that?