Hi The fundamental / third approach is one of several possible ways to go. You can also run an SC on the B and C modes to get thermometer data. Early implementations used a pair of independent blanks, one cut to be a good thermometer. Some have even gone as far as to mount a thermistor on the crystal.
No matter what you do, it adds cost. Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim Lux Sent: Thursday, August 30, 2012 8:55 AM To: [email protected] Subject: Re: [time-nuts] oscillators On 8/29/12 8:45 PM, Richard (Rick) Karlquist wrote: > > On 8/27/2012 11:45 PM, WB6BNQ wrote: >> >> >> A microprocessor controlled XO is a non oven crystal oscillator system >> that has >> additional computational control providing a bit more than just mere >> passive >> temperature compensation. The additional computational capability >> deals with >> having coefficients of that particular oscillator's behavior pre coded to >> compensate for the nonlinear behavior over a given temperature rang > > It doesn't use coefficients. It has a look up table of frequency vs > temperature. > >> >> A microprocessor controlled XO system allows for using cheap crystals >> with >> minimum processing time and costs. Because of limited storage space >> there is no > > No it doesn't use a cheap crystal. It uses a *special* SC cut crystal. > This crystal could very easily cost more than an OCXO crystal. > Isn't the crystal cut (and the circuit designed) in such a way that it supports both the fundamental and the third overtone simultaneously, and comparing the frequencies of the two (or, more accurately, fF- fthird/3) is how they measure the temperature, which is then used to look up the correction factor in a PROM. _______________________________________________ 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.
