software-trigger three multimeters at once

[Dominik123]

Hi!

I'm new to labview and I'm trying to trigger three multimeters (two Fluke 8845A and one HP 34401A) at the same time via GPIB. I found out that I have to use the "TriggerList" function, but I don't know how to use it.

How can I generate specific sampling-rate with this function and read the values from the instruments continuously?

Thanks for help!

Dominik

[Dominik123]

The triggerlist-function works now, but it works worse than triggering each multimeter for itself. If I look at the plots, the multimeters are obviously not triggered in the same moment.

Does anybody have an idea how to improve it?

Please have a look at my VIs.

Dominik.

[Dennis_Knutson]

You are sending a separate trigger to each instrument and placing code in parallel does not at all mean that the software triggers are sent in parallel. The GPIB bus is essentially sequential and your triggers will be generated one after the other. There is no way of telling which will be first and no way of telling how much delay will happen between the two triggers. There is a mechanism for triggering simultaneously. You need to use the GET (Group Execute Trigger) command. There is a TriggerList function on the 488.2 palette. You mention this in your post but you do not have this in your code. You could also try the VISA Assert Trigger Function. Be sure to only use a single trigger function.

[Dominik123]

I used Triggerlist in softwaretrigger1.vi but it works even worse than sending seperate trigger signals like I've done in softwaretrigger2.vi.

[Dennis_Knutson]

Sorry, missed the triggerlist function in your first VI. I saw the Initiate functions and I believe that is what is triggering the instrument. Get rid of that and try with just the triggerlist or the VISA Trigger.

Message Edited by Dennis Knutson on 12-04-2009 08:32 AM

[Dominik123]

If I don't use the Initiate function I get an error message:

Instrument reports:
-211,"*TRG/GET received but was ignored"
-230,"Data stale"
-420,"488.2 unterminated command"
+0,"No error"

[Dennis_Knutson]

Interesting. I'm obviously wrong about what the initiate does in the instrument. I don't have the instrument manual to study. You could perhaps try the VISA trigger to see if that behaves differently. A call/email to Fluke support might also help.