2008/10/23 Ron Smith <[EMAIL PROTECTED]>: > The text says the curve of frequency against plate thickness does not give a > straight line, but has discontinuities in it. These discontinuities they > call "stepping points" and are a result of edge vibrations coinciding with > sub-multiple frequencies of the wanted thickness vibration mode. The degree > of coupling between the wanted and unwanted modes varies with crystal > dimension. If there is zero coupling, the stepping points should not affect > the main oscillation. But perhaps even the smallest change in dimension can > cause it to cross one of these discontinuities and jump to and fro? I > suspect that crystal sensitivity to stepping or jumping may be correlated > with its temperature coefficient, although there are other factors > (including gravitational) that influence frequency of oscillation at very > small levels.
I have a counter that seems to exhibit a jump in it's timebase. From a cold state a fixed frequency connected to the input shows a gradual change as the unit heats up over an hour or two. Once it reaches a stable state it will stay in that state for a couple of days and then it will jump to a new stable state, and stay in that state however long the unit is switched on. This is repeatable each time I switch on. I have not observed the jump and there is no data output on the counter to be able to record the times that this happens. All I know is that there is a definite little jump after a long period of stability. 73 - Steve -- Steve Rooke - ZL3TUV & G8KVD Omnium finis imminet _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.