Synchronizing two cDAQ-9188 ehternet chassis

[v.derti]

I have setup a measurement chain that consists of the following hardware:

1. One cDAQ-9188 with three 9239 modules

2. Another cDAQ-9188, identical

3. A router for connecting the ethernet cables of the two chassis

4. an ethernet cable that reaches the computer.

Everything on NI-MAX is discovered and i implement a typical Labview DAQ file that operates within a loop (for continuous DAQ) and uses TWO separate DAQ Assistants, one for each chassis. The software runs smoothly, no problems occur and the data are saved. BUT: one chassis is not synchronized with the other (correct?).

My question: is it possible to somehow "synchronize" the two DAQ Assistants by using the PF's of each chassis and some functions from the Triggering and Advanced Timing tabs of the DAQ assistants?

Best,

Vasilis

[Duffy2007]

Hello v.derti,

yes, in this way they are not synchronized.

The best option is to buy a NI-9469, because you must share three informations between the two systems Start Trigger, Sample Clock and Sync Pulse ot synchronise the moduls, because the 9239 has an sigma delta amplifier onboard.

[bullit]

Hi Duffy2007,

thanks for your prompt response. I am aware of this solution but i am looking for a software than a hardware solution, as there is not budget and time to purchase a 9469. 

If i drop the use of DAQ Assistant, would something described here

http://www.ni.com/tutorial/5376/en/#toc6

help?

(or even better, could i transfer the above described functionality to DAQ Assistant?)

Best,

V.

[Duffy2007]

Hello bullit,

in this case you need three lines, but you only have two PFI connections on th 9188 you can share the start trigger, so both systems start on the same time, then you only have the delay of the trigger line and also if the aquisition runs over a long time the two oscillators will also make some deviations over the time.

And yes, you have to do this with the low level VI´s so you can route the trigger lines to the PFI port.

[bullit]

Thanks a lot Alexander! I will play with this solution and check the results. In any case, cross-correlation is always a good tool for delay estimation. Best, V.