VISA Read returns empty strings

[Ptc]

I am trying to communicate with a Tek TDS640 scope through GPIB. MAX will detect the instrument and allow me to communicate directly, but when I try to use the Instrument Library functions for the scope all the VISA "read" operations return with empty strings. The init function also claims that the device was "opened but not responding". However the VISA "writes" do not return a byte count (always zero) but the instrument responds to the instructions (on its display).

I can operate the scope throught the low level GPIB commands, but I would rather use the instrument library. What do I have configured wrong?

[Ray K]

Try using NI-Spy to capture the commands sent to and from the instrument.
NI Spy Tutorial

By double clicking on the lines in NI-Spy you'll be able to see the messages being sent. If those same commands work in a using GPIB commands, then you should uninstall then reinstall VISA.

Also make sure you have high enough version of VISA and the IVI engine installed. Most drivers require at least VISA 2.5 and IVI Engine 1.83.