VISA open timeout

[Heiko Fettig]

I am controlling a Tektronix TDS8000 DSO using VISA GPIB over TCP/IP. The labview 6i driver I wrote works well most of the time, but from time to time I receive a timout in VISA_open.vi (or in VISA_write.vi, if I remove VISA_open). Judging from the NISpy capture, both errors seem to be related to Labview trying to open a VISA session.

When I change the address to the GPIB bus rather than the GPIB over TCP/IP I do not receive any timeouts. Therefore it has to be related to the GPIB over TCP/IP.

Any ideas?

[Ray K]

Have you tried increasing the timeout on the VISA open? The default timeout is 0 sec. Also, what do you mean by GPIB over TCP/IP. Do you mean that you are using a GPIB-ENET/100? Or do you mean you are using remote VISA to access a GPIB resource on another machine?

[Heiko Fettig]

I tried increasing the timeout on the VISA open. Doesn't make a difference.
With GPIB over TCP/IP I mean, that the TDS8000 Scope, which is Win98 based, is running a VXI-11 server. This allows me to add the scope as a TCP/IP instrument in MAX and send GPIB commands to it over TCP/IP.

[Ray K]

Ok, VXI-11 clears everything up.
1) Make sure you have VISA 3.0.1 installed.
2) See if you have the same problem if you connect the computer and instrument using a crossover cable(or connect both to the same hub). The problem could be network traffic.
3) Make sure the instrument is always in the same state when you run your test. i.e. it isn't be used by another program or in a configuration screen

NI-VISA 3.0.1
http://digital.ni.com/softlib.nsf/webcategories/85256410006C055586256BBB002C0E91?opendocument&node=132060_US