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Stan or Patricia Griffiths
I hate to disagree, but the Navy Chief had a good point. The military, as
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you know, tends to "go by the book". The book in this case is a Tek manual and it specifies timemark generators. But more important than that, standard timing measurements on scope screens are made from the second graticule line to the ninth graticule line, ignoring the first and last 10% of the sweep. How can you do this if you don't have some reference mark at both of those points? A sinewave with one cycle spread over the entire screen won't do it. You could, I suppose, set your generator's frequency with the counter such that one cycle occupies 8 divisions on the scope screen . . . but even then, there is another problem. Where the sinewave crosses the second and ninth graticule lines, it is traversing the screen at a rather severe angle to those graticule lines. This can lead to errors in viewing this measurement that are well beyond the typical 2 or 3 percent specification of the the scope's timing. This does not mean that WE can't make some very useful timing measurements on scopes with counters and generators . . . we can! Most of us don't have to worry about the stringent rules of a military metrology environment like that Navy Chief certainly did. Extremely fast scope sweep speeds is exactly why Tektronix developed the concept of the "slewed edge" found in the CG551AP and later versions of that scope calibrator. I prepared and presented a stand up presentation on the "Tektronix Slewed Edge" at a metrology conference in LA in about 1979 when I was the Tek TM500 Marketing guru in charge or marketing the CG551AP. The slewed edge is an extremely noval idea on how to calibrate extremely fast sweep speeds, even if you don't have the required bandwidth to view sinewaves at those speeds. Stan w7ni@... dhuster@... wrote: Sometimes, time-mark generators are overrated. The advantage of them |
