That is the dirty little secret of crystals. Manufacturers will test the temperature response in one direction, but if you heat and then cool crystals and measure the frequency, they do exhibit significant hysteresis. I've not been able to get a supplier of TCXOs for me to characterize this as I don't buy enough. I just have to test them myself and toss the 10% or so that don't meet their specs due to the hysteresis. If you cycle the temperature up and down multiple times, the effect lessens, but after letting them sit for a while, it comes back. I also saw jumps at particular temperatures, but that may be due to the TCXO compensation.
Mark On Tue, Jul 9, 2019 at 4:00 PM Glen English VK1XX < glenl...@pacificmedia.com.au> wrote: > and non monitonicity in the device is the death of a control loops. > > My attempts at building good OCXOs using cheap AT crystals in the 90s > was thwarted by.... non monotonic bending crystals ! > > And everytime they would wake up, the monitonicity would be in a > different part of the control curve.... > > and they exhibited hysteresis, like defined steps , this seems to be the > case with most crystals, the harder you looked, the more undesirable > imperfections you found... > > > > On 10/07/2019 5:57 AM, David G. McGaw wrote: > > Leo - > > > > I do believe you mean non-monotonic, rather than non-monotonous. Not > > being monotonous is a good thing. :-) > > > > David N1HAC > > > > On 7/9/19 1:20 PM, Leo Bodnar wrote: > >> It's not very good, it is highly non-linear and even wor > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.