Detect identical USB equipment yet distinguish which USB card they are plugged i

[labviewman]

I have 2 identical Agilent DMMs that are connected to the tester via USB. I can easily detect them via 'Find VISA Resource' using USB?*::0x0957::0x0618::?*::INSTR for the search item. Since the serial#'s of the DMMs are not fixed (DMMs will be replaced with identical equipment when calibration is needed), I can't use them (w/o some code to prompt the user to decide...which I hate do allow to make a decision) to determine which DMM I am talking to.

Since part of the output of the 'Find VISA Resource' gives the USB board it is plugged into I figured for $30 I can easily determine which DMM to use for function A (i.e. if the response is USB1, than I know DMM1 is connected to that USB port), but, it still returns back USB0. I now have 2 USB cards for a total of 8 USB ports, but 'Find VISA Resource' returns the same info on each port, and if I compare all the VISA properties I read on each USB port (with the DMM plugged-in), they are all identical.

I checked NI's site, but something is going on to their site...can't get into much of the knowledgebase and the forums are not working well.

I'm sure I'm not the first one to come across this, so I'm am hoping someone else can offer some advice, preferably using NI software.

Thanks,

Todd

[MikeS81]

Hi Todd,

i don´t know if there is a function from ni to get what you need, but you can use the devcon.exe from Microsoft to get more information about all your USB devices.

Hope it helps.

Mike

[Dennis_Knutson]

I had a couple of test systems with several identical USB instruments. What I did was assign a VISA alias to each one (i.e. Instr_1, Instr_2, etc) and the program used the aliases and not the canonical name. When one was replaced for repair/calibration, the alias was first deleted and when the new instrument was plugged in, the old alias was reassigned to the new instrument. Pretty simple and quick.

[labviewman]

Devcon is not an option...VISTA does not like it.  If there is a VISTA-friendly version (I will search), that may work.

I don't think the VISA alais option (nice idea...I didn't even think of it) will work since they could remove both DMMs for calibration and I would not know their connectivity.

If only the USB[board] parameter worked as it seems it should (which board the USB port is from), it would be easy.

Thanks for the suggestions folks, but I guess I will have to allow the operator to decide if the SN change from the previously seen configuration.

Todd

[Dennis_Knutson]

Well, I had more than one removed at a time and had no problems with the alias method. It just took a bit of care by the technician doing the work. Remove one instrument and see which one disappeared in MAX. Replace that instrument and update the alias. The only time there was confusion was when all of the instruments were removed at once. I guess it's a question of trusting a technician to follow a fixed procedure or allowing an operator to make the decision.

[labviewman]

Yup, I see how that would work, but removing both at the same time can happen...I don't like trusting people to make the right decision...we all make mistakes.

[Dennis_Knutson]

I agree that people make mistakes all of the time. I would just rather trust a technician to follow some procedure than an operator to decide.