data reading delay using Keithley

[flafi]

Hi,

I'm programming Keithley 2602 to run a pulse sweep and give me measurements in real-time.  For example, the Keithley will take measurements every 5 milliseconds for ten seconds and send them through the GPIB USB.  To read the measurements with LabView2010 using VISA in syncron-mode, I'm using a "while"-loop.  The problem is that the Keithley device stops after exactly ten seconds, but the VI keeps reading the measurements, for another 5 or 10 seconds, as if there is some delay.  The total number of measurements shown in the diagram in VI at the end of the process is correct, but the vi just takes longer.  So I'm trying to figure out what the cause of the delay is, and how to fix it, because I need to make sure that it's only 5 milliseconds between each measurement, and not longer.  Also, in the diagram (in VI), the measurements seem to have the same width.

Thanks

[MHoffmann]

Hi,

I think the problem is the GPIB-USB. Can you test a PCI GPIB?

Michael

[flafi]

Unfortunately i don't have a PCI GPIB. But I thought the GPIB-USB would be fast enough to transfer data every 5ms without delay! Could it be on my VI ? As I mentioned before, i'm using a while-loop to read the measurments from the visa? 

Thanks

[MHoffmann]

Is the USB Port 1.1 or 2.0?

[flafi]

Hi,

It's USB 2.0!

Thanks