Instrument Control (GPIB, Serial, VISA, IVI)

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Problems with SCPI commands for HP 4156A

Hi I'm developing a LabVIEW program to perform current-voltage (I-V) measurements (as a student work project).
Has anybody some experience with the SCPI commands for the HP 4156A?
I downloaded the instrument drivers from the NI page and they're working fine (communicating via VISA and GPIB). But I have to modify the SCPI commands in LabVIEW's string constants to solve the following problem: 
it can occur that the measured values are "out of scale" which means that they are not properly displayed on the analyzer's internal display since the analyzer cannot perform auto-scaling while measuring. So it is difficult to monitor long-lasting measurements. That was one reason to develop a LabVIEW application to control everything via PC, most importantly the auto-scaling during measurements.
The drivers from NI ask the analyzer for an service request (SRQ for *OPC) and when it sends back that the measurement has finished the data is transferred to LabVIEW.
I tried to figure out some way to receive every new value while the measurement is still in progress, but although I have the SCPI command reference I was (not yet) able to.
Perhaps somebody as any hint how to do that?

Thanks

 
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Hi P.L,

i don't have experience with the 4156A, maybe we can help you with general SCPI/GPIB programming.

 

if there is a command for the required function, its easy to implement this, but please study the command manual. If you found some commands i'll try to help you.

 for general GPIB Documentation have a look at this kb:

Where Can I Find Documentation about the SCPI Specification?

 

cheers

Tobias

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Thanks for trying to help.
unfortunatly there will be no possibility to  achieve the desired function.

I contacted Agilent Technologies and they told me:

 

"...4156A could not receive any  GPIB command during measurement. It shows an error message. “Error 54: System busy, Measuring. Unfortunately it is not possible to acquire data during a sweep, because the entire trace needs to fill the array before the data can be sent to PC ..."

 

so I have to try somrthing else.

cheers

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