How do those compare with vectron's part : ? https://www.vectron.com/products/ocxo/mx-503.htm
There's also this patent. http://www.google.sr/patents/US20020005765 I don't really know if that's valid - it seems to propose something similar to the numerically-compensated oscillator in my rather old PM6666 frequency counter. On Wed, Nov 1, 2017 at 5:11 PM, <[email protected]> wrote: > >While crystal curves are indeed cubic, there are higher order terms in > >the curve. The “why” is something people get to write papers on. If you > >are trying to compensate to tight specs, you will see all sorts of > >stuff. It is not at all uncommon to see >9th order curves residual > curves. Indeed some of that is from residuals in the compensation circuit > as well as from the crystal. > > I’ve been trying to research this very topic! > > Can you point to some of these papers? > > I am trying to build the most accurate fee running, low power time base I > can. I am using an MCU, 32768Khz watch crystals, 0.5C accuracy temp sensor, > lots of thermal bringing between them, and mass around them. The idea is to > measure the frequency shift at all temps in the range, and even in both > directions (hopefully to capture some hysteresis) for each unit and then > use that database to compensate in software once the system is free running. > > I am trying to beat existing products like the Dallas DS3231 and Micro > Crystal RV-8803-C7-32.768kHz-3PPM-TA-QC, which use (I think) a similar > strategy. I’m hoping I can beat them by using more accurate temp tensing, > longer and more exhaustive calibration effort, and anything else possible! > > Can you give a quick explanation (or point to reference material) covering > the fundamental limits to XTAL compensation accuracy, and how to get there? > > That is, if I had an infinitely precise temp sensor and an infinite amount > of time to characterize an XTAL, what would be limits to how accurately I > could temp compensate it? > > Also, what are the limits of characterizing and compensating for aging? > > What other sources of inaccuracy would I need to consider? > > Thanks!!! > > -josh > > > > > _______________________________________________ > 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. > _______________________________________________ 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.
