testing an instrument handle

[tadk]

Labview 8.0, TestStand 3.5,

Is it possible to test an instrument handle in Labview to see if it is valid and not generate any kind of error if it isnt?

I want to close an instrument handle if it exists. This will generate a run-time error if the handle does not exist.

[Angela M]

Hello tadk,
You can run VISA Find Resources and look at the resulting list of interfaces.  You can use this list to verify of an interface is valid.  If I specific error is being generated, you can create a sub-vi to clear that error, and thus ignore that particular error.

I am not sure what your end goal is, but there is another discussion forum that discusses getting a Session ID by using a Call Library Function Node.  You might want to check this forum out.

I hope this helps!

Regards,
Angela
Applications Engineer

[tadk]

VISA find seems to only tell me what I already know. I know the string name of the instrument, which is also the name of handle which will be valid if the Initialize sub-VI for this instrument is successful in creating a session.

I was expecting I could test the handle similar to testing for a null pointers or file handles in other languages. If this is not possible the next best thing is to hide the run-time error dialog. How do I do this?

[tadk]

Just to be clear on the things I have tried already:

Disabling the pop-up of Simple Error Handler

Leaving the error cluster disconnected

Feeding a 'no error' type constant into Simple Error Handler

Creating a custom vi with just my handle, the Call Library Function Node, and  "IVI Delete Session" sub-VI.

None of these will suppress the run-time error which is something like 'invalid session handle'.

[Dennis_Knutson]

Do you have automatic error dialogs turned off? This is set in Tools>Options>Block Diagram.

[tadk]

No I didn't. I see that this applies for all VIs and not just the problem one.

thanks