difference between 488.2 and 488

[Tim Thomay]

This is perhaps a stupid question, but after all the work in the last
days to find out why my Keithley 2001 does not respond to any GPIB
command in LabView I want to know why this workarround is working.

My problem was that the Keithley 2001 did not respond to GPIB and VISA
commands in LabView. It was no problem to communicate with the
"communicate with the instrument" dialog in the MAX.

After several hours I tried the command subset of the IEEE 488.2. And
surprisingly there the send and recieve commands worked without a
problem.

Does anyone have an idea??

Tim

[LesHammer]

The plain 488 just defines the hardware.
The 488.2 standard defines the software.
Or more correctly, a set of standard command strings that compatible instruments will accept.

Les.Hammer@CompleteTest.com

[Brian_Powell]

I find this pretty surprising. Can you provide us with more information?

Were you using an instrument driver? What instrument commands were you sending? What errors did you get?

Thanks.

Brian

[JoshuaP]

Hey Tim,

That is correct. 488 refers to the hardware and 488.2 refers to the software. Hence 488.1 and 488.2 are very different, but both were designed to work using the IEEE-488 specifications. However, IEEE-488.1 was normally just called 488.

I hope this helps out.

-Josh

[Brian_Powell]

I guess I'm still finding this a surprising result and would like more information. While the others are correct about the roles of the IEEE specifications, both sets of LabVIEW functions (Traditional vs. 488.2) are built on top of NI-488.2.

At the bus level, there's not really much difference in how the two sets of functions work.

It would be interesting to see some NI-Spy logs that show failure with Traditional functions, and success with 488.2 functions. Can you provide these?

Brian

[Tim Thomay]

I would like to give you information from NIspy, but unfotunatly my
GPIB card has special drivers that don't work with NI Spy. So the only
error messages I recieve are the error messages of the multimeter
itself. because the error indicators of the labview gpib read and
write say OK.

So the errors the multimeter shows that the query is unterminated.
Sure first I thought it is something with the line termination. But
any option I tried to terminate the line there is the same error.

Perhaps this helps, it was no help to me ...

[LesHammer]

Query unterminated, along with Query interrupted, indicate a problem with either the string you are sending (syntax), or with timing. Since you have this working with NI-MAX make sure the strings in your program match those you used in NI-MAX. If that's not the problem, try putting delays in the program. That is, send a string, wait 10 milliseconds, get the response, wait 10 milliseconds. (There are some instruments that have problems with fast computers. They were designed in the days when the computer couldn't possibly get back to the instrument in 10 ms. Now that they do, the parser gets confused.)

Les.Hammer@CompleteTest.com