Handling multiple Channel Instruments in VISA

[mbuttman]

I am trying to find a way to addres instruments that more than one channel or slot (Agilent 8163A Lightwave Multimeter) using Max Utility Alias. Could there be a way to assign multiple aliases to the same GPIB instrument. Also is there somwhere to hide the channel number in the Visa session so my driver VIs can get that info after the session is openned?

[DiegoF]

Hi,

There isn't a way to acomplish this using the VISA resource names. VISA can only do what, in this case, GPIB can do.

Channel information is instrument specific. The GPIB specification does not define any mechanism to address different channels on the device. These are handle using the instrument-specific data commands.

The only mechanism that might be use to directly address channels is secondary addressing, but is the instrument manufacturer who defines this behavior. Check the documentation of the instrument to determine how different channels are addressed. If the instrument uses different secondary addresses to access channels, you could have different resource names for each channel.

DiegoF
National Instruments.

[mbuttman]

Thanks for the info. I guess what I am asking is if there is a way to hide the channel information anywhere in the visaconf.ini so I can just parse this info in my instrument driver.

[Makoto]

If you are trying to embed a "channel" context information into a VISA session, you can use VI_ATTR_USER_DATA attribute. This is a local attribute therefore the values are isolated between sessions even if they are associated with the same i/o resource. I sometimes use this trick for instrument drivers when allowing to viOpen for each channel (of output, input, trace, etc...) with the same i/o resource. However mind that you can't viOpen for "ASRLx" resource if other process has already opened the same one.

Makoto

[mbuttman]

That looks like a good place to hide the channel info. However one of my requirements is to not create more support files for my application. I would like to be able to store all instrument information in visaconf.ini. My application will be distributed on many machines and I don't want to have to manage yet another configuration file just for channel info. Maybe NI can address this in the next release of MAX. We should be able to edit the secondary address attribute of the VISA resource as listed in MAX.

[calvinkuek]

hi,
i m doing the agilent 8163A programming using labview 6.1.I m facing problem like error at sub-vi at error out status box.How can i correct that problem.I face the same problem with all the VI supply by Agilent.I try recheck the wiring already,but still can't find any mistake.
Thanks for helping.
Best regard,
Calvin