random errors using SCXI analog input on SCXI1100 
Author Message
 random errors using SCXI analog input on SCXI1100

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?


Sun, 31 Oct 2004 03:40:04 GMT  
 random errors using SCXI analog input on SCXI1100
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



Mon, 01 Nov 2004 00:53:19 GMT  
 random errors using SCXI analog input on SCXI1100
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?



Mon, 01 Nov 2004 02:18:00 GMT  
 
 [ 3 post ] 

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