Getting the same return string while reading multiple times from a GPIB instrument 
Author Message
 Getting the same return string while reading multiple times from a GPIB instrument

I'm having problems reading data from a GPIB instrument.
I'm using a sequence similiar to this:
1. Send a "MEAS:SCAL:PRES?" command to the calibrator to measure the
current pressure.
2. Read the result string sent from the calibrator.
3. Send a "SYST:ERR:NEXT?" query to check if an error has occured.
4. Recieve the error string from the calibrator.

When running the program, the error string sometimes contains the same
data as the pressure reading. For example, if the calibrator's
pressure output string was "1.0000000e2", the error string might be
"1.0000000e2" or sometimes just "20, No Errors", with the extra "2"
added to the normal "0, No Errors".
The problem appears to occure randomly, a rough estimate would be that
it happens one time out of 50 readings.

Are there any relevant GPIB card settings I can change to fix the
problem?



Tue, 10 Feb 2004 14:33:47 GMT  
 Getting the same return string while reading multiple times from a GPIB instrument
It looks to me that more data is send or data end is signalled to
early by hte iocard.
Maybe you should check the gpib bus cable speed. The default is much
too fast for almost all instruments. Put it on 2 microseconds (the
slowest speed). And we always disable autopolling, to prevent
asynchronous actions.


Tue, 10 Feb 2004 15:28:51 GMT  
 Getting the same return string while reading multiple times from a GPIB instrument
Try putting a short delay (say 10ms) between reading and making the
next request. This could just be a timing problem. The buffer hasn't
cleared before you make your next read.

     Rob



Wed, 11 Feb 2004 03:19:19 GMT  
 
 [ 3 post ] 

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