hp3458A simultaneous triggering

[Meelis]

Hi!

Has anybody a solution how to trigger two or more HP3458A digital multimeters simultaneously.
Either in Labview or using External triggering. The LabView's Group Excecute Trigger - GET nor *TRG does not seem to
work with these multimeters. *TRG is not supported by this multimeter according to the manual. The main point is that one multimeter is measuring voltage and the other current.
External TTL pulse should trigger multimeters simultaneously, but this is only if both measure current or voltage.
It seems that the delay after getting the trigger command (either external or from software) is bigger when measuring
current thant when measuring voltage. And this delay difference stays even when multimeters
are forced to use same delay using DELAY [second] command.

Any ideas how to solve the problem?

[Makoto]

Assuming you are using GPIB, one solution is use multiple listener operation.  Although you normally send a device message to a single listener, you can also send it to multiple listeners at a time.  How to do it is different depending on what library you are using.

If using NI-488.2 API from LabVIEW, you can use GPIB 488.2 "SendList" function that accepts multiple listeners through the "address list" parameter.

If using NI-VISA, you need open a separate session with "GPIB0::INTFC" then use VISA GPIB Command function (for ATN-TRUE part, specifying multiple listeners in it) and VISA write function (for ATN-FALSE part) to construct a multi-listener operation.

[rahulb]

considering this thread to be about hp3458A...can someone pls tell me how to calibrate hp3458A multimeter using LabVIEW?

[rahulb]

considering this thread to be about hp3458A...can someone pls tell me how to calibrate hp3458A multimeter using LabVIEW?

[Albert.Geven]

Hi Meelis

Maybe you have autoranging active for both systems and this can really influence measuring speed.

And if the current and voltage ranges are known you can exclude that problem by using fixed ranging.

[Meelis]

OK, I have found some more information about these multimeters and the phenomenon that puzzled me. It seems that the problem wasn't triggering at all, but the integration time. I now monitor the EXTOUT APER signal  (TTL) which shows the integration period. 

In these multimeters you can set the integration time of the measurement using NPLC command, 1 NPLC = 1/50 of a second (if used 50 Hz AC supply as it is in Europe). And when I set the NPLC numbers equal to both multimeters (I experimented numbers from 10 to 100) , the end of the measurement cycle was longer for the current (DCI) measuring multimeter. The time difference was exactly 2, ie. current measurement took 2*NPLC*(1/50) seconds and the voltage (DCV) measurement took as it supposed to be, NPLC*(1/50) sec.

But it got more weird. I usually cofigure the multimeters using LabView (GPIB bus). But when setting the NPLC form the display unit (let it be for exampe 50) and then measuring voltage (DCV), then the integration time is twice longer as it supposed to be, ie 2*NPLC*(1/50) seconds. Do I leave something important out what to cofigure or is there anything special about these multimeters?? What concerns about the AUTORANGE, then this is turned off and the range is set manually. The short table below gives an overview how these multimeters work at the moment. 

                                        NPLC command set via GPIB ------------------------ NPLC command set using the keyboard of the display unit

DCV measurment integration time     NPLC*(1/50) sec                                       2*NPLC*(1/50) sec

DCI measurment integration time       2*NPLC*(1/50) sec                                      2*NPLC*(1/50) sec

Meelis

[Meelis]

The problem has finally been solved. It turned out that for DC (voltage and current) measurements there can be used autozero function, which makes additional zero (input disabled) measurement after each reading and substitutes it algebraically from the reading, this doubles the integration time. When AZERO is OFF it shows corresponding info on the display. And here was the nut to be cracked. For DCI measurement you can not actually turn off the autozero function even if it shows it is OFF. So the integration time for measurement is still the NPLC times 1/50 sec, but  reading is finished within twice longer time.

Meelis

[e_madri]

hello

Can you help me please?  i have the same problem that you!

i need make the same project that you. But i dont Know how can i

synchronize those HP3458a..    Can you send me all the information about it please!

 i am making this simultaneous triggering in LABVIEW

Thanks

[Tina2]

Hi Makoto.

I like your answer for simultaneous triggering.

I'm also working with two HP3458As.

I'm intrested how to work with VISA GPIB Control ATN  ---> GPIB0::INTFC.

I put it between two GPIB Write functions.

If my first HP is connected two PC, I supose that I don't need to use VISA GPIB Control ATN before writing to it.

Is this true?

Kristina.

[patphp3458a]

HI , I am new user using HP3458a and like to what commands i can use ( in GIPB) to set 2 HP3458A at the same time  to make DC voltage measurement from 2 meters. I am trying to cut down the Trigger time so like to know if  I can trigger

both at the same time. so I cna save trigger time if done in parallel.

Thanks