intermittent 'empty' reply to measurement request EABO (6)

[HZW]

Hi,

My system is a Dell PC running Windows XP Professional (service pack 3) and I am using a PCI GPIB card to communicate with 2 instruments. I am using the NI tools version 3.1.1

I'm having some problems understanding an intermittent problem I have with an electronic load (N3300A) which I control using GPIB. From time to time - so not always - I get a timeout exception from the .NET VISA library: 'Time limit exceeded to complete operation'. I've put the tracer on it and I see the following:

 

The GPIB instructions I sent request a measurement from the device. Very shortly after sending the command, I receive what looks like an empty string (Receive(0, 0x0005, "", 20 (0x14), STOPend (0x100)).

Is this an effect of a timeout? But it arrives way before the 10s timeout I set are over. I could increase the timeout, but I fear that would not help.

Or is VISA library not happy with the reply that was sent (an empty string)? And expected more data, which didn't come. After which it raised the error. But that does not seem to be what this trace is suggesting. Can someone please clarify? This error tends to happen the first time my program is run; after that it doesn't happen as often.

[HZW · Accepted solution]

I 'figured it out' some time later. I was using both the NationalInstruments communication software as the Agilent (now Keysight) software. Both have their own way of doing communication. By removing the Keysight software parts the issue has been massively reduced.