Problem with AI acquire 
Author Message
 Problem with AI acquire

As far as acquisition goes, it looks like you have the right code.
You have separated the waveforms into graphs properly as well.

I may need a little clarification on your signals.  When you say
"spike is superimposed with the sine wave", what do you mean?  I'm
assuming that you mean that you have two inputs -- a sine wave, and
spikes on an otherwise 0 volt signal.  Is this correct?


Sun, 25 Sep 2005 21:32:06 GMT  
 Problem with AI acquire
the first wavefrom should be a +/-10V sinewave only and the second
waveform should be only a constant dc voltage with spikes (abt 20usec
The problem we are facing now is that the second waveform of the
acquire waveforms have a scaled down sinewave(abt 3-4V) with the
spikes riding on it. how to get rid the scaled down (abt 3-4V)
sinewave. How to acquire just the spikes in the second waveform only
while at the same time synchronizing the  spike waveform to the
sinewave in the first waveform.


Mon, 26 Sep 2005 11:31:16 GMT  
 Problem with AI acquire
Which card are you using for your acquisition, and how is it set up
(differential, single-ended)?  I'm wondering about the ground signal
not being hooked up properly.....

As mentioned before, your code for obtaining the signal and displaying
it are correct.  The signals should pretty much be synched (offset
only by the interchannel delay, which is extremely small--on the order
of nanoseconds).

The only other thing I can think of is that the input impedance of
these cards is very high, and you will get crosstalk between channels
if there is not sufficient impedance on the input line.  In looking at
your data, however, I don't believe this is the case, because your
spike "sine wave" is out of phase with your first channel, which would
not be indicative of this crosstalk.  Now that I think about it, not
connecting the ground correctly should have about the same effect....

Can you verify on an oscilloscope that your spike signal indeed is not
imposed on a sine wave?


Mon, 26 Sep 2005 20:27:33 GMT  
 Problem with AI acquire
I'm using PCI 6025E for my acquision. I'm not sure if I'm using the
correct setup but the current setup is RSE(single- ended). how do i
know if the ground signal is being hooked up properly?

I've verified that the spike signal is not superimposed on a sine wave
on a scope. Just by acquiring the spike signal alone without the 50hz
reference sine wave(just one channel), the output is a clear waveform
of spikes. Why is the spike signal riding on a sine wave when acquired
together with the reference 50 hz sine wave?

I don't have this problem when i acquire the 50 hz sine wave and the
spike signal individually by 2 separate acquire But if i
do this, the 2 signals will not be synchronised. Hence, i changed to
use acquire Though synchronised, the spike waveform is
riding on an unwanted sinewave. What have gone wrong? How should I
solve this problem?

Mon, 26 Sep 2005 21:50:42 GMT  
 [ 4 post ] 

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