GPIB device appears to fill up after about 15000 polls using L-V 6.1

[jdd103]

I use a Keithley 2700 Data acquisition unit with GPIB interface to LV6.1 I require a large number of measurements over a long period of time. It appears that when I exceed 15000 polls of the Volts using the GPIB interface The data stops being sent correctly. Instead of giving the true voltage it gives 0.0 most of the time and occasionally the first value of the voltage eg 3.0 instead of 3.45734. I have tried clearing the Device and various other commands but I don't seem to be able to clear it. If I turn the Multimeter off it also doesn't clear. However, when I turn off the computer or change the GPIB address of the device I can use it again for another 15000 polls. How can I clear the problem with
in the LV enviroment?

[Matthew C]

Hello jdd103,

Thank you for contacting National Instruments.

From what you have described, you�re unable to acquire more than 15000 voltage values from your instrument without having to reboot your entire system. I am going to suggest a few possible solutions.

First, ensure that you are using the correct instrument IVI drivers in your LabVIEW application. You can find these drivers by searching our instrument driver network at http://www.ni.com/idnet. I believe the link you may want to use for the Keithley 2700 is as follows:

http://zone.ni.com/idnet97.nsf/9b2b33e1993d877786256436006ec498/882db8a61094a30686256d8a0071ac12?OpenDocument

If you are not already, include a wait until next ms multiple function in any loops you may be using in LabVI
EW to ensure that you are not overburdening your system resources.

Finally, also ensure that you are initializing and closing your reference to the instrument in the application. If you are already doing this, try nesting your actual acquisition code within another loop that occasionally closes and reinitializes your reference to the instrument.

I hope this helps! Let me know if you have further questions.

Matthew C
Applications Engineer
National Instruments

[Joelj]

Why is it necessary to close and reinitialize the reference to the instrument?