Looking for Examples: Process Control with Data Acquisition and Rapid Shutdown

[elward]

GerdW,

Thanks very much for the information.  I will have to look into getting some other hardware or just live with the slower response time.

[Bob_Schor · Accepted solution]

Your requirement for detecting a Critical Event and responding within milliseconds suggests you require a LabVIEW Real-Time environment, possibly cRIO-based (but I'm not sure I'd recommend running it on a PC, even with a Real-Time OS installed -- you want something designed for Real-Time, even if (like NI's PXI systems) it has an Intel chip inside).  I have PXI experience, but limited experience with cRIO ...

Bob Schor

[GerdW · Accepted solution]

Hi,

the expand on Bob's message:

I have experience with cRIO and can recommend it for time-critical event handling.

But you will need to learn about LabVIEW-RT - and maybe also LabVIEW-FPGA to get most out of that hardware…

I'm looking for examples of process control loops with … high speed (<1ms) shut down responses

This qualifies to use the FPGA inside of a cRIO target. (The ScanEngine might operate at that sample rates too, but it becomes less capable at those sample rates.)

But you need to combine it with DAQ modules allowing you to read your thermocouples that fast.

And you need thermocouples being able to allow such quick temperature responses…

Conclusion:

1. Write down all of your requirements.
2. Call your local NI sales rep to discuss them and receive a quotation…

[elward]

Thanks to all of you for the information.  I really appreciate how supportive this forum is.  It looks like I'll need to make some hardware changes along with my code.

I know I'll have many more questions going forward, but I'll start new threads for those.  Thanks again.

[AnalogKid2DigitalMan]

I would attack the power cut-off from a hardware approach:

Feed the T/C into an external limit alarm unit (with a SSR output for quick response, not a mechanical relay) that is set to the desired temperature limit. When the limit is reached the SSR turns off.

The SSR of the alarm limit is wired to another SSR that is rated for the voltage/current of the power supply. SSR goes between the power supply and the sample under test.

A limiting factor may be the time constant of your T/C- use the smallest possible unsheathed junction you can find that can handle your upper temperature range.

-AK2DM