When do I open/close intrument sessions (VISA / IVI) within a TestStand Execution?

[Caribe]

I would like some advice about opening and closing visa sessions,
or other kind of sessions when working with instruments...

How do you do that in TestStand? Which is the right way to
work with instruments? Should an "open" and a "close" command
for each step be executed? Or on the SETUP sequence once "open"
and on the CLEANUP sequence once "close" for each instrument
session?

I read already a lot of Stuff about VISA and working with instruments,
but which are the guidelines for opening and closing sessions in a
TestStand execution?

I appreciate a lot your help!

Best regards,

- Caribe -

[Watermann]

hi Caribe,

in my oppinion it's regardless whether you use visa session in teststand or another software.
if you don't use or open another session outside the running sequenze i would prefer to open it once in the beginning and close it at the end...
but perhaps anyone can give you better advice who deals more with this...

greets!

[Caribe]

Thanks Watermann,

I hope this is the right way, but I am also not sure...

Regards,

- Caribe -

[Dennis_Knutson]

I don't think it makes a great difference either way except in one type of case. In most of my applications, I have to control a UUT though a serial interface. In the custom steps I use, I open and close the VISA session. The advantage for me in this case is that if I or a debug technician sets a breakpoint or pause on failure is set, we can open up Hyperterminal or Procomm and examine the UUT configuration. So, opening and closing the VISA session in the step can be helpful when an external app needs access to the resource.

[CT]

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@Caribe wrote:
I would like some advice about opening and closing visa sessions,
or other kind of sessions when working with instruments...

How do you do that in TestStand? Which is the right way to
work with instruments? Should an "open" and a "close" command
for each step be executed? Or on the SETUP sequence once "open"
and on the CLEANUP sequence once "close" for each instrument
session?

I read already a lot of Stuff about VISA and working with instruments,
but which are the guidelines for opening and closing sessions in a
TestStand execution?

I appreciate a lot your help!

Best regards,

- Caribe -

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I had same question when I started using TestStand. But it really depends on what instrument you are using and how you use them. I use some HSDIO cards that will generate digital waveforms along the sequence, I need to keep the session at each generation so that I don't have to configure the cards before each waveform is generated. Same with acquisition, by keeping the session handle I can acquire at any point in the sequence. In other test, a spectrum analyzer is configured differently for each reading/measurement, I do open/close for each setting there. I am also looking into session manager that allows you to create custom session besides IVI, VISA, VXIPlug&Play sessions. But I am not sure if it's useful in TestStand.