I have been using a 34401A DVM very successfully in my VB6/VBA Software until recently.
For various reasons, I had to start using a test station computer with my software. It is Windows XP 2000 SP3. I still use VB6 and VBA to program test software. The problem also occurs with the Agilent IO Connection Expert.
Here is the problem. I can perform the ID? command and received the expected string data back. If I perform MEAS:VOLT:DC? then meter will beep and I receive a visa timeout error.
So far the only fix I have found is to re-install the IO Connection Expert software 16.3.17218.1 and select the REPAIR option. It will be good for a day, maybe two if I leave the computer running. If I re-boot during the day, I am still okay. If I turn the computer off and then turn it back on the next day, I get the same time out errors (but not with the ID command). I have to re-install. It is that bad, that I copied the IOLIBSUIT installation program to my desktop.
I control an Agilent E3632A, Agilent 11713B, Agilent 33250A and Tektronix TDS3054B with the same program without any issues with them. I re-arranged my GPIB cables several times. The problem is only with the 34401 DVM and only with certain commands. I have replaced the 34401A in my test system with another 34401A (we have many) and the problem is the same.
I can not run a new version of Agilent VISA or Connection Expert because I think v16.3.17218.1 is the latest for Windows XP. I am tempted to go back to version 15.x and give it a try. I am pulling my hair out. It appears to be a GPIB command timing issue. I would suspect my software but as I said, the exact same error occurs in the Connection Expert program.
Please, does anyone have experience with GPIB VISA communications with the 34401A DVM. If I can not resolve this, I may look for another DVM with GPIB communications capability.
BY THE WAY, the exact same program works flawlessly with version 17.x IO ConnectioN Expert under Windows 7. Unfortunately for various reasons, I am stuck with Windows XP on this test computer.
Dave Pulling His Hair Out