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whats the difference between VISA and GPIB?
BrentSchenk
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09-25-2008 11:16 AM
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The reason i am asking this question stems from a problem i am having.
I am using an MXA N9020A to aquire Burst Power measurements and i'm using labview to automate and issue the commands. If i connect to the device using VISA (which is how i pretty much have connected to other devices) and i issue a command :INIT:TXP it will start the burst power and then freeze the measurement disallowing me from changing channels to measure other channels' burst power. If i use the GPIB VI instead it will not do this and I am capable of channel hopping to measure other channel powers. I really dont have a reason to use VISA other than to keep it uniform with everything else in the application but why is this?
TV_Enable
NI Employee (retired)
09-26-2008 10:19 AM
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Hi Brent,
Thank you for your post. Before I can answer this question, I'll need a little bit more information from you. Which version of VISA are you using? Also, are you running in asynchronous or synchronous mode? I look forward to hearing from you soon.
Regards,
Todd V.
09-29-2008 04:56 PM
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Hi, thanks for helping me out here. I'm using LabVIEW 8.5 here and shortly i will be installing 8.6 i do believe. I have not specified whether I'm using asynchronous or synchronous mode to send the GPIB commands so i'm assuming whatever is the default. I also have not specified the mode in which i am sending the packets so i would assume mode zero. thanks for any explanations!
Brent
TV_Enable
NI Employee (retired)
09-30-2008 05:14 PM
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Hi Brent,
Thank you for your quick response. This should not be happening, as the VISA VIs merely make calls to the NI-488.2 DLLs. Which version of NI-VISA and NI-488.2 are you using? Could you also attach both of your VIs (the 488.2 one that works and the NI-VISA one that doesn't)? Also please perform one NI-Spy capture for each VI, and attach the two resulting screen shots. If you need assistance performing the NI-Spy capture, you can find more details here.
Regards,
Todd V.
10-02-2008 02:23 PM
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I apologize for the delayed response but in the midst of doing this i had deleted anything with VISA communicating with the MXA. When i went to recreate it all i was getting the same results that i had with GPIB which were still not favorable. I will need some time to get back to you with all this as i will do some more investigating myself. Thanks for the prompt replies though!
-Brent
