I am working with a system that has 8 GPIB power supplies, about 150 feet of cable and a GPIB-130 cable extender. I am controlling the power supplies using VB.net using the NI 488 driver v2.7.3. With all 8 supplies connected everything works great. If one of the supplies is turned off my software application receives the timeout error and will reestablish communication when the power supply is turned back on. The problem I am having is if one of the power supplies is disconnected (from the middle of the daisy chain) from the IEEE bus (the cables are removed but are still connected together allowing the other supplies to communicate) then things do not work very well. The supplies will return syntax errors and display text for commands that were not sent. And my application will not communicate with many of the power supplies left that are still connected. Resetting the power to the extender seems to help for a short time. My software application is also running on a second test cell that has 4 GPIB power supplies and no cable extender. We are unable to create the problem above at this test cell. Any suggestions?
