how to use two 2400 and two 6485 in Labview simultaneously

[Nilesh-ncsu]

Hi,

I want to use two 2400 and two 6485 simultaneously on GPIB.

One set of 2400 and 6485 in voltage sweep mode and other set is in constant voltage bias. 

I want to trigger all at the same time for measurement. 

I have 3 terminal device like phototransistor. one 2400 sweeps voltage and 6485 measures photocurrent. another 2400 provides constant voltage bias and 2nd 6485 measures photocurrent. I can use these in separate pairs but I want to use it in one program. 

Do you know how to do it using LabVIEW?

Thanks

[Blokk]

You have to setup a hardware triggering between the Keithley units. I think they support hardware triggering, look at their back panel for connectors. Also, as I remember, you can find VIs in the corresponding LabVIEW drivers which deal with triggered operations. Besides you are lucky, because proper VISA drivers were just released for the picoamp meter (6485) very recently (2017 April)!

Snippets showing the triggering functions of the two drivers (Tree.vi):

edit: here is some older post related to your question too: https://forums.ni.com/t5/Instrument-Control-GPIB-Serial/Using-Keithley-2410-Sourcemeter-and-Keithley...

[Nilesh-ncsu]

Thank you for your reply.

[cstorey]

Hmm, I'm guessing the photocurrents are very small in your devices?  Otherwise why not just use the 2x2400 and have them source and measure at the same time? You could simplify your life with a pair of Keithley 2600s, 6482s or 6487s.  Those all have lower current measurement capability (+triax cables) and voltage sourcing functionality so you'd only need 2.

Do you care about speed?  If so you'll want to use external trigger cables, and you'll want to look at the Keithley trigger model very carefully for both instruments.  You'll need to set appropriate trigger Source-Delay-Measure conditions for each instrument.

Otherwise, if speed is not important you can do everything with LabVIEW controlling the timing of measurement using dataflow.  I do this with 3-4 instruments when exact measurement timing isn't an issue.

As was pointed out the Keithley driver VIs will be very helpful.  Look at the example programs for a good place to start with 2 instruments...then extend to 4.  Post code if you need help.

[Nilesh-ncsu]

I don't care about speed. Slow measurement won't be a problem. 

I have Trigger line wire but I can connect 2400 and 6485 one set and another set separately. I cant connect all four instruments using trigger link. 

So if I can use software trigger it would be good. I will post code.