Give commands to two keithley2400 at the same time

[sixers0130]

Hi All,

I would like to give commands to 2 keithley2400 at the same time and wish them to do current sweeping simultaneously at real time. That means I have run two loops simultaneously. It seems to be difficulat yet not so difficult since there is no dependency between these two loops... Is it possible? using what structure? The solution i use right now is a simple true/false button with two case structure. And of course it won't work. Sometimes two units will run simultaneously but most of the time they will run in order.

[altenbach]

Why are there two case structures, you could just put all in one. Same difference.

I don't see the loops you mentioned.

Aren't there trigger capabilites to link the two instruments (trigger link)?

[Dennis_Knutson]

GPIB is sequential by design. You need to configure each one by one and then trigger both to get s simultaneous reading.

[Dennis_Knutson]

I should have paid closer attention to your post. With two identical instruments, you can use the low level GPIB functions to program multiple addresses. The GET can be used as a software trigger.

[sixers0130]

Loop I mean two case structures... sorry for the wording. Yes I can give SCPI commands and use trigger link to trun them on simultaneously, and I'm just seeking possibilities to use labivew to give commands to these units simultaneously. 

[sixers0130]

Thanks for your input. Can you give me more info about GPIB functions "GET" to muliple GPIB address? Any reference?

[Dennis_Knutson]

Just go to the GPIB palette and have context help turned on. I'm posting from my phone so I can't provide the details. Look at the functions that have an array as an input for the addresses. GET stands for Group Execute Trigger and is a way to trigger multiple instruments with a software command.

[rolfk]

While multiadressing may get you "synchronous" enough it's by no means a guarantee that both instruments will really react equally fast when receiving the trigger command over the GPIB bus. For true hardware synchronized operation you will have to use the trigger bus on the back of the device to connect them together, select one of the 4 trigger lines to use and set them up correctly on both instruments, one as input and one as output and then send the trigger command to the device that drives the trigger line. That will give you synchronisation to microseconds accurate. GPIB multi addressing will be in the range of several milliseconds and sequential GPIB in the range of maybe 100 milliseconds. 

[sixers0130]

Thanks for the input rolfk! I know by giving commands and using trigger link I can get complete synchronization. But actually my goal here is just to make them sweep at appoximately the same time and it doesn't need to be totally synchronized. Few millisecond is within my tolerance. These two units work as seperate system and there is no data flow between these two, so that's why I'm seeking possibilities to use LabView to achieve this other than giving commands. Without using commands, I can only make one of them sweep first and the other one go next. 

[sixers0130]

Dennis, thanks for your reply. I looked up the function and see I can give a list of addresses, but I'm confused at:

Even though I can trigger these devices at the same time, at what step do I give them SCPI command? How can I do that? Since I still need to give them command sequentially. Or by using triggerlist function I can no longer use SCPI command and built-in functions from Keithley?