offset voltage when many input signals are involved 
Author Message
 offset voltage when many input signals are involved

When I connect 2 analog signals to chan 0 and chan 1: say chan 0 = 4
V; chan 1 = 2 V. There is an offset of .02 V on chan 1 (i.e. the
reading is 2.02 V).  All other channels 2-7 are grounded. I am using
differential mode.  However, when one channel is selected for data
acquisition only, then the problem disappear.


Sun, 15 Aug 2004 01:51:30 GMT  
 offset voltage when many input signals are involved
Sounds like you might not have enough interchannel delay so the second
channel doesn't have time to settle. The AI Config.vi routine has an
input for specifying the amount of delay to insert between reading
channels on a scan. The default value is a -1 which tells LV to figure
it out on its own--sometimes this value is too short.

To see what LV is selecting, there's a subVI inside AI config called
AI Clock Config that outputs the value LV selected. Probing that point
while your code is running will give you a starting place for
adjusting the interchannel delay.

Mike...



Sun, 15 Aug 2004 03:46:35 GMT  
 offset voltage when many input signals are involved
Bingo!

It's working.  Thanks
Gaston



Sun, 15 Aug 2004 04:57:53 GMT  
 
 [ 3 post ] 

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