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Is that possible to synchronize PCIe 6361 at 2Msps and cDAQ9188 AI module at 25.6k sps (Multiple system synchronization)

 

Before I run too far, I need to confirm if PCIe system can be synchronized with compactDAQ system?

If it is possible, the timebase is different as PCIe has 100mHz, and cDAQ has 80Mhz, I can not export sampling clock from high speed pcie to cDAQ.

 

-----------devices---------

 

PCIe 6361 (dev1)  Timebase 100MHz and 20Mhz, ref clock 10Mhz,

target sampling rate 2M sps

It has all PFI and USER1, RSTI connector


cDAQ 9188   Timebase 80MHz and 20Mhz,   PFI0 and PFI1, no RSTI suport ,  

target sampling rate 25.6k sps (NI 9234 use only 51.2 or 25.6K?)


see attached device routes.

 

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I try export the PCIe start trigger to PFI0 and wired to PFI0 (I also try APFI0) BNC terminals on cDAQ as trigger input, but there is error/or cDAQ will just not start even PCIe can start.

see attached

 

When I purchased cdAQ and PCIe card, the NI engineer once said it is possible by triggers. but I am not sure how it is possible.

 

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Maybe I can buy another PCIe card to support vib sensor (NI 9234), using RTSI cable to connect two PCIe card, seems more practicle.

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Regarding the exporting of triggers, this should work, as long as the physical connection is stable and each task is receiving the correct terminal inputs, could you tell us what values you're using?

 

Regarding synchronization, the first question is whether you need the 2MS/s acquisition or 1MS/s would suffice. We offer 1Ms/S CompactDAQ modules (9223, for instance).

 Assuming you need this then:

 

To synchrionize voltage at 2MS/s and vibration, your best bet would have to be using PXI Express instead of PCIe, as the timing bus on the backplane would allow for no-drift synchronization between them (you'd have to export the start trigger from the DSA device (for example an NI PXIe-4492) to the NI PXIe-6361. They will both reference to the 100MHz backplane clock, giving you the best results with the easiest setup.

 

We don't offer a PCIe sound and vibration device, so you'd have to use a PCI 4461 and the reference clock will have to be 10MHz over RTSI, which will give you a little more jitter and latency and will affect your analog specifications slightly. You'll also have to share your start trigger

 

If you choose to stay on CompactDAQ and PCIe, you could generate a 10MHz Clock with one of the on-board counters of the chassis and export it through the PFI connector to the PCIe-6361 and use it as a reference clock, as well as using the same clock as the sample clock timebase of the 9234. This will slightly affect the analog specs of the 9234 and will lower its maximum rate to about 39KHz.. You'll need to export your start trigger on the other PFI terminal.

 

I hope this helps.

 

Daniel

 

 

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Thanks, I wire the cDAQ start trigger signal to PCIe, I found no sqare wave. Now I doubt how can I export the start trigger.

 

Is start trigger has same frequency as sampling rate, so I need a oscilliscope to get the start trigger export correctly at first.

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I try to connect PFI0 from PCIe to cDAQ PFI0, start trigger seems working, but the when I wired out (T-type connnector) to oscilloscope, there is no square wave captured, why? I also try wire trigger PFI0 to AI of PCIe, I did not capture the square wave.

 

After the program is running, I disconnect the trigger cable, the program can still working, while if I disconnect at the beginning, the program will not start DAQ. I still wonder why the start trigger is NOT fired every sampling period (each iteration of while loop)? Like the retriggerable example on youtube, shall I put the start-trigger setup in a while loop?

In order to make sure long term sync, sync edge should be issued every 1 second! If the sync relies only the first edge, sync error may accumulate as time going.

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Hi,

 

The start trigger is a single pulse (At the beginning of the acquisition) and then remainings low, you won't see a continous waveform. You may be interested in exporting the sample clock of the device (Square wave with frequency of the acquisition).

 

Regards,

Applications Engineer
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