Bob Benward <rbenward@...> writes: > > Continuing this discussion, I have included a PDF showing the past 30days of > EFC. Amazingly, the drift has reversed direction! Anyone have any insights > into this behavior? Each data point represents 10 seconds. >
I have found that three things can cause this behavior over a short term (days) which do not involve failure of the standard itself ( in no particular order ): 1) Power supply. Most standards are immune to this but, if your EFC circuit or phase detector involves active circuits, it can show up. 2) Grounds. Bad grounds or ground loops, especially those that share current with the oven heater can cause unexplained drift. However, these usually have a diurnal temperature signature unless your set up is very climate controlled. Screw terminal grounds or connections can "age" and change things. Best to ahve everything soldered. 3) Cheap components, especially resistors. I recently had this driving me nuts. Carbon comp. and the 2 cent metal film resistors have large temperature coefficients and are even sensitive to humidity. Go for the <10ppm / deg C metal film or SMD resistors. Some caps also can be tricky if the circuit involves large caps. Leakage is a problem in high impedance circuits and can be unpredictable and non-constant. Finally, there is literature that supports resonators can reverse their ageing slope. However, this is rare. I hope this helps. I have been there, scratching my head while the system seems to have a mind of its own. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
