How can I manage four NI5112s in one system?

[diaoxiumin]

Now in system there are four NI5112s.All the NI5112s have the same configuration and all their inputs are connected to the same pulse signal source.All the NI5112s use analog edge triggering and the trigering source is the input signal.So all the NI5112s should be trigered at the same time.However,when I fetch the waveform with the function niScope_Fetch in sequence,I find that the values of wfmInfo.absoluteInitialX vary a lot(10-70ms).why?

[Ben]

I wil side step the "why?" and make a suggestion.

The 5112 is capable of multi-device syncronization. Us one of the boards to trigger on th analog signal, and then have the other boards trigger off that board via RTSI.

Ben

[Josh H]

There are two things that need to happen in order to guarantee the synchronization of your 4 NI 5112s. First, you have to share a reference clock that all of the boards can use to align the phase of all of their clocks. That way they will all take samples at exactly the same time. Second, you have to share a trigger. You need to use an edge trigger on one channel and then send a digital trigger to the other boards across RTSI (PCI) or the Star Trigger Line (PXI). I have attached an example of how to accomplish this (in PXI) that will soon be on the web.

[Michael_S.]

The reason the absoluteInitialX values differ from one board to the next is probably due to the fact they are not armed at the exact same time, so the individual board timestamp clocks start at slightly different times. This is also due to the fact that the boards are running completely independent of each other.

I have attached an example program that will be available on the Developer Library for High-Speed Digitizers shortly. It is set up to synchronize two boards in PXI, and to increase it to 4 simply expand the slave board array and the additional propogation delay arrays to have 3 inputs (Master board will be the 4th board). Also the VI is setup to have the master board in slot 2 of the chassis and take advantage of the Star Trigger capabilit
ies of slot 2 in the PXI chassis.

Let me know if you are using PCI boards and we can see about modifying the code for PCI.

Good Luck on your project!

[diaoxiumin]

I just want to syncronize the clocks for my 4 NI5112s in order to let all the signals sampled by them have a common timebase.For some reasons of my signals,I cannot sample all of them when one triger comes.That is to say,although I want to share a reference clock for all the NI5112s,I still want them to be trigered
independently.Could I do this with PXI NI5112?