O-scope waveforms

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Ed B.
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O-scope waveforms

Post by Ed B. » Sat Jun 23, 2007 7:42 pm

My 76 year old brain is deteriorating and I need help.

What is the proper spelling of the name of the guy (not an American) after whom various displays from an oscilloscope are named ?

It is something like "liss-a-juice". I can't find him in the American Heritage Dictionary.

Thanks for any help.

Ed B.

rshayes
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Post by rshayes » Sat Jun 23, 2007 8:20 pm

Lissajous

Ed B.
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Post by Ed B. » Sat Jun 23, 2007 9:44 pm

To rshayes

Prompt reply - That is exactly what I needed -thank you very much.

Ed B.

Dean Huster
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Post by Dean Huster » Wed Jun 27, 2007 8:27 pm

I hated Lissajous patterns from the word "go". With the advent of triggered sweep scopes and frequency counters, the technique is pretty much passe except for their application as "special effects" in the motion picture industry. Trouble with the darned things is that unless the two signals are phase-locked, it's a shot in the dark for any accuracy. Kind of nice to not have to deal with the things anymore!

Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

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Robert Reed
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Post by Robert Reed » Wed Jun 27, 2007 9:24 pm

I have to agree with Dean on that one, however we had to adjust an extremely accurate secondary standard( well into the negative eleventh order of magnitude) to a cesium beam primary standard, and at those kind of accurracies, we could only do it with single loop " lissy" patterns on an oscilloscope. We even had to use a stop watch to time the flops and so to pull it within specs. Very time consuming process but the "Lissy patterns made life easier here.

Dean Huster
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Post by Dean Huster » Sun Jul 01, 2007 5:51 pm

Robert, it would have made more sense (to me at least, for what that's worth), to externally trigger the scope with the standard and run the unit under test into the vertical input. With the sweep set at a faster rate, you can accurately and more-quickly calculate the offset of the two using the timebase speed. It's a lot easier and faster to use the horizontal graticule as your "ruler" than it is to count the flops. And setting the initial frequency of the DUT is orders of magnitude faster that way than it would be with a the "lissy" pattern. Figuring that frequency standard offsets are so small, it takes a long time for a measurable "lissy flip" while you can track nanoseconds of shift easily using the timebase and external trigger.

Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

Robert Reed
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Post by Robert Reed » Mon Jul 02, 2007 12:51 pm

Dean
I suppose that method would work for less precise adjustments and I agree it would be faster. But we were dealing with accuracies well into the ELEVENTH order of magnitude here and also adjusting not only for match, but also phase lock between the two. Not even the best of scopes have any kind of precision to be trusted under those conditions. Even the most miniscule of trigger jitter ( and they all have this to some minute degree) would introduce an unnacceptable error at this level of prescision. I should make it clear that even though these were Lissy patterns, they were in thier most fundamental form and eventually came down to a 45 degee line on the scope display. This is the manufacturers reccomendation and the accepted way of adjustment for standards of this accuracy.

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