Hi everyone,
I'm trying to interface with two 15 y/o Newport PM500-C motion controllers by using the instrument I/O assistant. The assistant is using VISA interface, and the motion controllers are connected to each other with GPIB cables while the computer is connected to the whole setup with an NI GPIB-USB-HS adapter. My VI is able to read and write to the controllers for the first one or two dozen minutes of my code running, but, eventually, the assistant will start returning only empty strings instead of the position indicator strings it was happily returning before. During this time, I will also be unable to write to the motion controllers using the VISA Write function, which returns error code -1073807339, but may be able to do so with the NI MAX 488.2 communicator, though even this sometimes returns an error stating that there is no device connected even though all physical GPIB connections are secure. Restarting the 488.2 communicator clears this message. When the empty strings are being returned, the NI Spy reveals that the computer is only sending "VISA Get Attribute" commands instead of the query and write commands it showed when correct strings were returned. Restarting my VI temporarily corrects the problem, but it always returns after awhile. I am wondering if this connectivity problem is caused by the obsolescence of the motion controllers, or if there is something I can try to prevent the I/O assistant from returning empty strings in the first place. Any ideas would be appreciated. Thanks!