Communicate between PXI RT and CDAQ

[Rannoch]

Is it possible to communicate from LabVIEW RT on PXI to an ethernet CDAQ (One that does not have a controller on it such as the 9188XT)?

Or are their better alternatives to a hybrid centralized vs remote data acquisition system?

Problem:

We like using PXI/PXIe because of its high channel count and support for various cards.  We like using LabVIEW RT because we run into less problems with windows crashes, updates from IT, and we can generally process data faster and more efficiently (determinism is not a requirement).  However we have systems in which we need to measure say 96+ thermocouples on a jet engine and it would be easier to connect them and possible other signals to a chassis closer to the engine or one that can be mounted to the cart/adapter with the engine.  Is it possible to use DAQmx on PXI RT to communicate to the ethernet chassis?

I believe it is possible to use a controller on say a CDAQ or CRIO chassis and communicate between them using TCP/IP or Shared Variables etc etc.

[esoDerek]

Hello Rannoch,

There are a couple ways you could tackle this! 

1. Use a host PC to communicate with LabVIEW RT on PXI and with the ethernet cDAQ. If your data can be acquired separately and consolidated on a host computer, this may be the easiest solution. 

2. Communicate with a USB cableUse a USB cDAQ, connected to the PXI RT controller. As of LabVIEW Real-Time 2012, our PXI RTOS controllers can communicate with USB-cDAQ devices via a USB cable. Unfortunately, I have not yet found any information about using ethernet DAQ - this may not yet be supported. 

3. Use the NI MXI-Express RIO Expansion Chassis. This is a chassis specifically designed to be used in the way you mentioned - it is controlled by a PXI (or other) controller and allows you to communicate with a RIO chassis. 

http://www.ni.com/white-paper/10938/en/#toc4

Options two and three will be limited in their reach - if your PXI chassis needs to be more than a few feet away from the cDAQ chassis, I would definitely recommend communicating that data over a network, and using a host computer to take your data! Could you provide a little more information about your physical setup? That might help narrow down your options!

Thank you,

Derek B. 

PS: If you haven't purchased your hardware yet, it might be a good idea to get in touch with the NI sales engineers! They're pretty used to talking through the right options for an application. You can call them at (888) 280-7645!

[Rannoch]

Thanks for your information.  We have not purchased hardware as of yet.  I've been talking to the sales engineer for my area.  We asked him several questions and are waiting back for a response.  I think our team may just pull thermocouple wire to the PXIe chassis.

General Info:

The distance is around 100 feet.  So neither option 2 or 3 are possible.  It does look like I can use a cRIO expansion chassis using an ethernet connection.  Unfortunately I cannot use DAQmx for this.  I was hoping that DAQmx could be used as the one communication API to talk to all of NI instruments but it does not appear to be so.

[esoDerek]

Hello Rannoch,

Thank you for the update! Just to be clear, you can indeed use cDAQ and DAQmx for this application - but you would need to be communicating that data to a host PC (not your PXI controller). If you have a host PC where you're monitoring and processing your data, you can communicate with both your PXI RT Controller and an ethernet cDAQ chassis. This would allow you to stay within the DAQmx API!

Using a very long thermocouple may work - but you'd run into a lot of noise over 100ft. Please be aware of this! There's a great document on this (linked below):

http://www.ni.com/white-paper/3344/en/

I'd encourage you to speak with your sales engineer to learn more about this - and of course, please let me know if you still have questions. Good luck!!

[grkmsngr]

Hello,

I tried your 2.method but my USB cDAQ 9174 showed up under PXI RT controller as a USB:RAW on NI MAX. How to configure this? Thanks for your answers.

https://forums.ni.com/t5/LabVIEW/Communicate-with-USB-cDAQ-9174-and-PXIe-8840-RT-Controller/td-p/403...