synchronous measurement with two HP 34401 DMM's

[Jochen Hohl-Ebinger]

how can i trigger two digital multimeter synchronously with labview?

[allaba]

you need to use the 'group executive trigger' command which is a special
byte sent in GPIB command mode and which triggers all instruments which are
armed to react on this trigger event.

In Labview this low level GPIB programming is pretty much hidden from the
user, so here's what you probably have to do (I don't have a HP34401 handy,
so I couldn't try):
The HP34401A driver is included with the Labview distribution and you'll
find it in ...\instr.lib\hp34401a\hp34401a.llb in the labview folder.

There is a VI called "HP34401A Config Trigger.vi" which arms the Voltmeter's
trigger system. Set the control 'Source' to 'Software' and do this for each
DVM to be triggered.

After arming the trigger system the actual triggering should be done with
the 'VISA Assert Trigg
er' function (found in the VISA function pallette).

If you don't want to use the VISA GPIB calls, you can GPIB-send the string
":TRIG:SOUR: BUS;" to the two DVMs and subsequently use the "TriggerList"
function from the GPIB 488.2 pallette to do the triggering.

Since the trigger systems of modern Voltmeters tend to be fairly complex it
might be worth reading the DVM's manual to understand the dependencies...


"Jochen Hohl-Ebinger" schrieb im Newsbeitrag
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> how can i trigger two digital multimeter synchronously with labview?

[sasko]

What about external trigger ?

I use this command but it seems that I need trigger for each voltmeter, which produce phase error

[Dennis_Knutson]

Of course you can use external trigger. You would only get a phase error if you are using two separate and independent trigger sources. You just have to wire the same single trigger to both instruments.

[sasko]

Thanks for answering,

I use one trigger for both HP 34401 ei one wire is connected to both, but I still must press button twice to get readings

I can send VI, if it would help

Sasa 

[Dennis_Knutson]

You're going to have to explain what you mean by 'press button twice'. Attach the VI as version 7.1 or older please.

[sasko]

External trigger on HP34401 can be pulse 0-5V or simple switch which connect hot end to ground, I use switch , one for both Voltmeters

If I read good manual for HP, after trigger intialization and read command, multimeter should go to the "wait for the trigger" state and when this trigger occurs it should transfer data into buffer, internal or external, so that I can download this data.

I have paralellel thread for  both instrument, it seems ther is some problems with RQS.vi ie how to handle one for both

I have to use for low frequency(<5 Hz) AC measurement.

VI is attached, thanks in advance

[Dennis_Knutson]

It will take me a while to look at your program in detail and your wiring style is a bit confusing but I'm not sure at what point in your program you are generating the external trigger. I think for testing purposes, I would pull out the RQS code from the read VI and maybe even send a message to the screen to tell you to generate the external trigger. I don't think it will matter whether you do the RQS polling in parallel or sequentially. Say you first check instrument 1 and it waits for the trigger. As soon as you issue the trigger, the instrument will gnerate a service request and the Wait for RQS will stop waiting. If you then run the Wait for RQS for the second instrument, it will have received the trigger at the same time as instrument 1 and generated the service request at the same time. The Wait for RQS on the second instrument will immediately return.

[Tina2]

Hi.

I have one question to ask.

What will happen or is it possible to send through NI-488.2 command "Send" TARM SGL to both instruments/DMM's at the same time?

Thanks.

[Tina2]

I'm using two HP 3458A .

Also, how about to set TARM AUTO, TRIG SYN, NRDGS 1, TIMER/SYN?

Thanks,

Kristina.