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what should I check vs intermittent triggering failures?

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what should I check vs intermittent triggering failures?

Postby hillp » Sun Sep 23, 2007 11:22 pm

Have experienced failure to trigger intermittently over the past several years on a succession of 4 Dell laptops running Windows; always running the latest non-beta version of Picoscope on a parallel port ADC11. We trigger on voltage rise from a pressure transducer.

In the past the most common failure to trigger came when it seemed PS had locked up waiting for the trigger event. Last year I even installed a mechanical device to blow air into my pressure transducer to check triggering before re-arming to wait for the real pressure event. This has at least warned me if PS had locked up and I can force it to quit from Task Manager and re-launch it. This triggering test has helped but we still had one instance at the most innopportune time last year.

Are there some things I could check to help maximize the chances of reliable triggering?
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Postby picojohn » Tue Sep 25, 2007 9:21 am

Hello hillp,

You allude to triggering reliability but, it is unclear to me whether you attribute that entirely to the lock-up problem or, is it an additional problem.
Could you please clarify?

Could you also let me know what the typical interval between trigger events is and, how fast the transition from your transducer is?

Regards
John
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Postby hillp » Wed Sep 26, 2007 2:24 am

Hi picojohn; thanks for listening. Most failures were due in the past to the computer locking up waiting for the trigger. We learned to arm the trigger only shortly before the event (less than 2 or 3 minutes); this seemed to help. Getting a newer computer also seemed to help. (Boy did we have problems with a laptop running Windows 98!) Last year we only had one failure, but unfortunately in the confusion we didn't find out what caused it. I don't think Picoscope had locked up, because I have a completely blank trace I must have triggered in some manner after the failure to trigger. (Actually as I write this I wonder if it triggered and somehow collected a blank trace.)

We use a single trigger on voltage rise from a designated one of three transducers and save each trace manually after it's captured from -0.1 second to +0.9 second. We do this several times a day, no faster than a half hour between events, during maybe 10 or 15 days a year. The signal goes past the trip point in several milliseconds and stays high for almost the whole 0.9 seconds, so it's not that the event was only a blip too fast to be seen by the relatively slow ADC-11.

I'm baffled; if this failure happens again I will immediately perform the manual air blast injection to the transducer (which I now do as a dry run before every pressure event; this tests the entire signal train) to see if it triggers on that. If it doesn't, it would seem that the signal didn't reach the ADC-11 or PS has locked up. Windows Task Manager (after crtl-alt-delete) could tell me if PS had locked up, because when this has occurred in the past, 2 Picoscope entries were seen in the TM, and CPU usage was usually 100%.

No obvious cause seems apparent here; I was fishing for anecdotes or past experience from the forum that might lead me to software conflicts, bugs, tips, etc. Luckily we're more reliable today than we've ever been, but not quite where we want to be yet.
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Postby picojohn » Wed Sep 26, 2007 1:24 pm

Hi hillp,

Sometimes, legacy products which rely upon the parallel port can behave unpredictably as a result of the changes that newer operating systems have made to the way in which the LPT is used. Often, such issues can be resolved by using our parallel to USB converter (http://www.picotech.com/usb_parallel_port.html). However, before trying that, you may wish to consider upgrading to one of our newer USB scopes, such as the PicoScope 2202.

Anyhow, should you experience problems in the future, then you could send your setup details to us at support@picotech.com so that we may take a look.

Regards
John
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