Newbie GPIB Question About Multiple Devices

[Pawel_Kowalski]

Hello, I am going to be working on reproducing a test bench that will communicate over GPIB. I have never worked with GPIB and I am looking for a list of equipment to buy to reproduce this system and have a question. I will have 2 GPIB devices, one on address 9 the other on address 22. One device is a HP volt meter and the other is a HP switching unit (3488A). The old test bench had 2 GPIB cards for this but my question is do I really need 2 GPIB cards to communicate with these 2 devices? From what I read up to 15 devices can be hooked up to the same GPIB port. Is the way the software will need to be written any different as a result of daisy-chaining devices?

[Albert.Geven · Accepted solution]

Hi

GPIB indeed addresses upt to 15 devices and you don't need two gpib cards.

The software addresses always by means of an address so the only thing you have to take care of is to assign different addresses to the instruments and to make sure that all calls are sequential, not parallel because it is just one bus.

[Dennis_Knutson]

You might have to rewrite it. With 2 controllers, you can communicate in parallel. With a single controller, you communicate sequentially. The ability to communicate in parallel can have some benefits with multiple measurement/source instruments but I'm not not sure how you would use this with a meter and a switch. Typically, you would command a switch operation (opne/close), wait for the operation to complete and the switch to settle, then take a reading. You would have to look at the program to determine how the commands to the 2 instruments are sequenced.

If you do decide to use a single controller, about all that you would have to do is change references to the second controller. If you are using VISA, you would change from GPIB1::addr::INSTR to GPIB0::addr::INSTR.

[Pawel_Kowalski]

Thank you both for the reply. Dennis, sorry I marked Albert's reply as the solution right before you answered.

I do not think that the readings need to be ran in parallel, I am reviewing the old C code for the test bench now.