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joel

Looking for stream-processing applications

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I'm doing research on LabVIEW applications that needed to process data while it was being continuously acquired (stream processing). Examples of these applications are ones that have a cycle time of 1KHz or above and is not performing single-point control. I'm interested in applications where you have

a) Been able to represent this in LabVIEW with no problem

b) Been able to program it but had to do things that you might consider "ugly"

c) been unable to get the application to work in LabVIEW or with NI drivers (and either resorted to a different technique or gave up)

This is, of course, to see if there's anything we should be doing to make these applications easier to program. In searching the forums, most of the questions are around TCP/IP or streaming to disk which isn't quite what I have in mind.

You can either post the applications here or you can e-mail me.

joel.sumner(AT)ni(dot)com

Thanks!

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Hi Joel:

I did something for a client a while ago where we were reading a data stream coming in from an Nicolet telemetry system, converting it from the telemetry stream using a Nicolet telemetry demodulator card, scaling the data to engineering units and streaming that data to disk. I recall that we were running at about thirty channels and five hundred hz or so.

Is that the kind of thing you are interested in? If so, let me know and I'll try and get in touch with my client and see what happened on the project.

(At the time I was involved, the answer to your question was definitely (b) : "ugly" . There were problems with the beta .DLL provided by others, so the only way to make it work was to Launch LV, wait for it to crash, Launch LV again, and it would work from then until the next time the computer needed to be re-booted. I'm sure they've progressed from there since them, this was a few years back.)

Best regards, Lousi

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I did something for a client a while ago where we were reading a data stream coming in from an Nicolet telemetry system, converting it from the telemetry stream using a Nicolet telemetry demodulator card, scaling the data to engineering units and streaming that data to disk. I recall that we were running at about thirty channels and five hundred hz or so.

Is that the kind of thing you are interested in? If so, let me know and I'll try and get in touch with my client and see what happened on the project.

Yes, I'd be interested in hearing more about it. Please email me

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What comes to my mind is temperature testing VI's with thermocouples, on SCXI chasis. I think some of NI's own examples in that area do just what you ask. I think the processing is simply getting a "mean" temperature to record though.

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We are doing Labview-based radar data processing which may fit into your stream-processing definition. We have a non-NI A/D which acquires data and passes it to a bunch of DSPs for initial processing. The data is read from the DSPs by Labview, where we do further processing and display.

For such applications, we always use two parallel loops - one acquisition loop and one processing loop - using LV2-style globals to pass data from the acquisition loop to the processing loop. Obviously, average processing loop speed has to be fast enough to not fall farther and farther behind the data acquisition, but the parallel loops with the LV2-style global is critical in preventing processing or display latencies from causing a buffer overflow in the DSPs.

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