Why the mesured reading thru GPIB are different from from the instrusment in Labview ?

[YCHENG]

Need help on above problem, I never faced this problem before . I have several instruments connected thru GPIB interfacing, the problem is when I measured the frequency from the frequency counter thru GPIB by labview it give me a totally different value from the frequency counter.eg, the frequency counter display showed 405Mhz but the mesurement read back by the GPIB using Labview gave a value 4 , another example is mesured the current comsumption from the power supply, the power supply showed 0.025A but the reading from the labview is 1699.

The test program i used for some time but got no problem , only it happend when the GPIB card got some problem and i replaced and reinstalled the NI-488.2 driver , then the problem occured.Pls advise. Thank you.

yc

[ScottieB]

Yc,

I would closely examine the GPIB bus transactions in your program.  Is the program receiving incorrect data, or is it mis-parsing correctly received data?  You may want to reveal more about your program--are you using an instrument driver?  Did the instrument driver change recently?  When you chagned GPIB cards, what was the old card and what is the new one?  Did you change NI-488.2 versions?  From what to what?

You also mention that you've got several instruments, is there any possibility that the primary addresses were changed on them so that you are reading from the wrong one?  Have you tried this with just 1 instrument on the bus?

Thanks,

Scott B.
GPIB Software