using 40 ethernet cDAQ chassis with 1 PC: is it safe/feasable?

[GianlucaB]

For a structural health monitoring solution we are offering a configuration using about 40 compactDAQ:

20 cDAQ-9184 (4 slot)

10  cDAQ-9188 (8 slot)

10 cDAQ-9181 (1 slot)

managed by a LabVIEW SW in 1 PC. Anyone already tried a similar configuration.

Do you think there are driver limitation, hardware limitation, software limitation with this architecture ?

Gianluca

[SSPTest]

Goodmorning Gianluca,

the real issue regards the "time-syncronization"! If you want to carry out a "well-done" structural health monitoring, with this number and kind of devices you are not in the condition to syncronize all the devices toghether. The acquired data aren't correctly time referenced. This is principally due to the cDAQ-9184. It doesn't support the PFI signals (useful to share the time-base between the devices). Even if you choose another cDAQ device that support PFIs, you will need to plug both Ethernet cable and coaxial cable through the devices... I don't think that this is the best solution for this application. If you're going to start this project I suggest you to evaluate the opportunity to use a cRIO based architecture, in which the syncronization between the targets is ensured by an EtherCAT communication.

For more details or informations, please don't hesitate to contact me through the support sistem:

call us: +39 02 41 30 91

http://www.ni.com/it-it/support.html

specify this issue and ask about me!

Thx for writing in this community forum!

Regards,

Stefano Fois

National Instruments Italy- Staff Application Engineer

[GianlucaB]

I'm pleased to know that the real issue is time synchronization. Do you confirm I will note have issue in managing as many chassis using a single PC?

Thank you in advance

Gianluca

[SSPTest]

Goodmorning Gianluca,

no troubles about the number of devices plugged in one pc... as I already said, the issue is only a problem of data syncronization.

If you want to use the DAQ targets (instead of RT targets), you may also adopt this approach to syncronize the time-base:

with the module NI 9469, you can connects in daisy-chain (or tree pattern) your all devices in the way to ensure the clock routing and triggering functions.

Again, with the devices you chose, the only caveat to this is the cDAQ-9181, just because it one-slot chassis... so if you use the c-series syncronization module (NI 9469) you don't have the possibility to add any other I/O modules, and vice versa...

Personally, since it seems a very big and important application, I suggest you to well evaluate the project specifications in the way to identify the perfect harware matching. If you need help, we are here for you!

Let me know, 

Stefano Fois.

National Instruments Italy, Staff Application Engineer