# 2 is not true. A cut has either two turning points or zero. Where both turning points exist there are two temperatures at which the temperature coefficient of frequency is zero. Cut 0 on figure 6 at https://coloradocrystal.com/applications has no turnover point. It is neither fish nor fowl. Cut 6 is the normal AT curve with extremes of ±16 ppm for -55° C thru +105° C. All curves normally intersect at 25° C rather than the 27° C shown. 25° C is half way between -55° C thru +105° C. Curve 6 is the Tchebychev polynomial y=4x^3-3x and curve 0 is y=4x^3.
Consider the standard AT cut which has turnover points at -15° C and 65° C. The lower turnover would ordinarily not be used in ovens. A set point error of ±1° C in the upper turnover point at 65° C results in a frequency error of +14.875·10^-9. For cut 0, that same ±1° error in room temperature results in a frequency error of ±31.25·10^-12. This is an improvement of 476 to 1. You apparently have not thought thru what improvements are possible with thermal coolers/heaters. Among these is near instant warm up and greatly reduced power for thermal management. πθ°μΩω±√·Γ WB0KVV ---------- Forwarded message ---------- From: Bob kb8tq <[email protected]> Date: Fri, Jun 2, 2017 at 12:43 PM Subject: Re: HP5061B Versus HP5071 Cesium Line Frequencies To: "Donald E. Pauly" <[email protected]> Hi Which statement is not true: 1) That there is a tolerance on the cut angle of a crystal? 2) That true zero temperature coefficient only happens at the turn? 3) That heater based controllers are impossible to build? Bob On Jun 2, 2017, at 3:40 PM, Donald E. Pauly <[email protected]> wrote: That is not true. I say that thermal coolers have made ovens obsolete. A zero temperature coefficient at room temperature is easier to hit than a zero temperature at the upper turnover point when such a thing exists. See curve 0 in Figure 6 at https://coloradocrystal.com/applications/ . πθ°μΩω±√·Γ WB0KVV On Friday, June 2, 2017, Bob kb8tq <[email protected]> wrote: > > Hi > > Any real crystal you buy will have a tolerance on the angle. In the case of a > crystal cut for turn > the temperature will be a bit different and you will match your oven to it. > If you attempt a zero > angle cut, you will never really hit it and there is no way to compensate for > the problem. > > Bob > _______________________________________________ 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.
