Synchronize PXI DAQ and SCXI DAQ

[TCjr]

How can I synchronize analog inputs into an SCXI-1102 ( Slot #1, 4-20ma) and a PXI-1050 (Slot#3, voltage) that are both contained in the same mainframe (PXI-1050).

thanks, Terry

[Timothy_S]

Terry,

Generally speaking, when trying to synchronize two measurements, you need to share the sample clock and the trigger source for the acquisition between the acquiring devices. 

In your case, with the PXI-1050, could you explain to me a bit more about your setup?

You're using an SCXI 1102 input module in the SCXI portion of the chassis, but what DAQ device are you using to control the SCXI scanning with? To control the SCXI modules with a PXI DAQ card, the card simply needs to be in the last slot of the 1050, where it can then use the local bus to drive the SCXI portion.

What PXI DAQ device are you trying to use for this?

If you are simply trying to drive the SCXI module with the PXI DAQ card, then it should only require you to drive the SCXI module from the last slot of the PXI chassis with the DAQ card, and then use the appropriate sample clock and trigger source to sync it with the rest of your system.

Timothy

Applications Engineer

National Instruments

[TCjr]

Tim,

Thanks for your reply and I'm sorry for the long delay in getting back with you.

My current setup is that I have two PXI-6221s in slots 3 and 8 in the PXI portion of the PXI-1050 and an SCXI-1102  in the SCXI portion of the PXI-1050. I currently use the PXI-6221 in slot 3 for acquiring two voltage signals and the SCXI-1102 is used to acquire 12 current loop (4-20ma) signals. I currently don't use the PXI-6221 in slot 8 (the last PXI slot). I'm currently collecting data using the PXI-6221 in slot 3 and the SCXI-1102 in slot 1.

As I think back, I remember I had some problems trying to get the SCXI product to work, but I learned that there needed to be a specific card type in the final PXI slot for the SCXI portion to functional. So, when I was coding I just continued to use the PXI-6221 in slot 3 due to the absence of a card in the final PXI slot. Once the final PXI slot was filled I started working with the SCXI cards.

I'm wanting to share one of the signals from the SCXI-1102 with the signals on the PXI-6221. I should also tell you that the SCXI-1102 and the PXI-6221 will be acquiring at different frequency. That's what makes me wonder if it would be easier for me to just hardwire that same signal to the PXI-6221 that is currently sent to the SCXI-1102? What your thoughts?

tks, Terry

[Timothy_S]

Terry,

Thanks for getting back to us here.

It may be easier to wire that same signal to both cards, but while I go through the information you have posted here about your setup, could you explain a bit more about the signal you are trying to share, and what its purpose it/how it is being generated? That will help me make the proper suggestion for you moving forward. Thanks!

Timothy