GPIB Coding for the HP4191A Impedence Analyzer

[Matt C.]

Hi everyone,

I am trying to use Labview and an HP4191A Impedence Analyzer to make some basic frequency measurements. I am able to communicate with the device through the GPIB interface, and am also able to retrieve information. However, I cannot successfully perform a sweep or even move the measurement marker so that I can read the impedance/phase information at frequencies other than the default one set on the instrument at the time I perform the measurement.

Because the 4191A is so old, I'm got my GPIB code from the programming manual for the HP4291A, which is supposed to be compatible with the 4191A. I suspect that this difference might be causing my problems.

In particular, after setting up and initiating the instrument, I am initiating the measurement and reading it as follows:

'INIT;'

'DISP:TRAC:MARK:ALL:STAT ON;'

'CALC:EVAL:Y1:XPOS 300MHz;'

'CALC:EVAL:Y1:DATA?;'

which comes straight from the programming manual. In the code above, 300 MHz is an arbitrary frequency. However, rather than being returned the data at 300 MHz, I am returned the data at whatever frequency the analyzer is currently set at.

If anyone has worked with the 4191A and/or GPIB before, can you verify whether my GPIB strings are valid or not?

Thanks,

Matt

[Matt C.]

 Sorry, that last line of code there is supposed to read:

'CALC:EVAL:Y1: dATA?;'

The forums emoticons took over for a bit there 🙂

[smercurio_fc]

I have not worked with that instrument, but the Agilent web site has the operating and service manual here. It's 84MB, so I hope you have a fast link.

[MattBradley · Accepted solution]

I have worked with the 4191A and, as I recall, the commands are nothing like any other instrument I have seen.  You really need the manual.  I think the 4291 would probably take the old 4191 commands, but the 4291 ALSO has new commands.

IIRC, the sweep parameters were something like this:

A=(start freq)

B=(stop freq)

C=(step size?  or was it number of pts?)

Good luck with it....

[Matt C.]

Matt - you're right, the commands for the 4191A are completely different from the 4291 - probably because of its age. I went through the manual before, but when I saw their GPIB section, the strings were so convoluted and so unlike anything I've ever seen before that I assumed it was referring to something different. When I gave it a try, though, it worked fine.

Guess you never know until you try!

Thanks for your help guys.

[JamesDt]

Has anyone done anything on interfacing with the 4191A since Matt C's last post?

(If not, what would creating a driver for it entail?   Should I be looking at doing it with LabView or something else?)

Matt C. : Would you mind posting the code you used on the 4191A?

Thanks!