TDS 2014 Scope UNL Command

[clue1019]

Hello,

    I recently upgraded my computer from a Dell Optiplex GX150 to a GX260.  I am running LabVIEW 6.1 on the machine as well as VISA 4.3.  I am using a CEC PCI GPIB IEEE 488.2 card to communicate with a TekTronix TDS2014 oscilloscope.   Everything worked fine on the old computer, which used an older version (2.3) of VISA.  However on the new machine the "UNL" command sent via VISA write at the end of my VI to put the oscilloscope into local mode does not work.  The oscilloscope does not respond when I send this command using GPIB or VISA from within LabVIEW.  Alternatively, the command does work when I send it directly from the VISA interactive control module outside of LabVIEW.  Any suggestions on the cause of this problem.  I was wondering if the new version of VISA (4.3), may not be compatable with the older version of LabVIEW (6.1).

     Thanks,
     Chris

[chris_amadasun]

Hello,
Have you tried adding a delay right after you make the call?
Also can you post a NI Spy log of your LabVIEW application and also one with the commands sent using the VISA interactive control.

[clue1019]

Hi,

    I have a little more information about my problem.  It seems that after the oscilloscope finishes the collect data and it is transfered to the computer via GPIB, something is left in GPIB bus so that when the UNL command is written to the bus is not read correctly by the scope.  With the oscilloscope in romote mode, I can exit LabVIEW, and when I restart LabVIEW, I can send just the UNL command using VISA_Write and the command worsk fine.

     Thanks,
     Chris