how to acquire data from several equipment almost simutaneously

[well-ted]

I set up one measurement with several tester such as network analyzer, spectrum analyzer and multimeter. Now I want to use LabView to collect test data from all these tester almost simutaneously. Hardware or software trigger may be used. A couple of micro seconds of delay may be acceptable. I don't know how to find this kind of topic on this web. Besides, is there some codes which can be used directly? Thank for any suggestion.

[John_Howard]

Wether or not it is possible to do what you want depends entirely on what instruments you are using, and how they are connected. This is possible of they are PXI instruments in the same PXI chassis, but if they are bench top intruments connected via GPIB cable you might have a problem getting microsecond synchronization. Can you give us more information?

Thanks!

[Evan]

Does it matter whether the data gets to LabVIEW synchronously, or just that the data was acquired with microsecond synchronization?

If you need the data in LabVIEW synchronized there is no real way to use desktop instruments and GPIB, due to the fact that they are all sharing the GPIB bus. I guess you could try multiple GPIB boards, to speed up the transmission by having fewer instruments per board, however the communication will not be truly synchronized.

If the data just needs to be acquired synchronously, then you will just need to see how to set up shared triggers and clocks etc for the specific hardware you have.

[Dennis_Knutson]

Just to add a little more to what John and Evan have said. The gpib bus has no dedicated trigger lines unlike vxi or pxi. A gpib instrument may or may not have a dedicated external hardware trigger input and may or may not have a software trigger command. If the instruments support it and you have a physical trigger event that can be detected, then the exteranl hardware triggerwould be the best thing to try. How quickly the instruments respond to the event is something that you'll have to determine from the instrument manuals. There is always some finite amount of delay. If no hardware trigger is available, then you can try software software triggering. The instruments can be configured and then you would issue the GET (Group Execute Trigger) command. Again
there will be some finite amount of time required for the instruments to respond

[well-ted]

Thanks for your reply.
I still have some questions as below:
1.Is it true that one GPIB card can only deal with the data from one instrument like network analyzer?
We have some instruments such as HP 8510C, Agilent PNA E8358A and multimeters. I thought these instruments are GPIB based. So as you said, it is impossible to collect the data from those instruments via GPIB cable at the same time. IS it right?

2. Besides, we do have NI PXI. But I don't know that PXI have any relations with GPIB. Can you tell me if I can synchronize the data from different instruments mentioned above using PXI? BTW, what is different of PXI and GPIB and are they compatible?

Thanks again.

[Dennis_Knutson]

1. You can retrieve data from only one instrument at a time but with triggering, all instruments can acquire simultaneously (or nearly so). This is usually more important.

2. With a shared hardware trigger, synchronizing GPIB and PXI is easily done.

GPIB is a 16 bit parallel bus with 8 data lines, 3 handshaking, and 5 management lines. The maximum transfer rate is nominally 1 Mbyte/s. GPIB instruments are stand-alone boxes with their own power supplies and user interface (buttons, knobs, screen, etc.). The PXI bus is an extension of the PCI bus used in PC's. It has dedicated trigger lines and a much higher performance with a throughput of 132 Mbytes/s. Many measurement systems combine PXI and GPIB instruments. The most powerful, I be
lieve, have an embedded controller in the PXI chassis. These will provide hardware triggers to the PXI cards, some have a GPIB controller, and some have a trigger input/output for your external instruments.