Societe Suisse Pour L'industrie Horlogere Management Services S.a.

Hubert Matthey

Raymond Huguenin

Martial Voumard

Jean Engdahl

The inversion temperature of a quartz piezoelectric resonator is determined y exciting the resonator at its resonant frequency, bringing the resonator to a first temperature T.sub.h, obtaining the resonance frequency f.sub.o at the temperature T.sub.h as a standard of comparison for the subsequent measurement of resonator frequency variations, bringing the resonator to a second temperature T.sub.f and measuring the relative frequency spread (f-f.sub.o /f.sub.o) while the temperature is varying from T.sub.h to T.sub.f, detecting the maximum value of the frequency spread, and deducing the temperature at which the maximum value occurs. One of the first and second temperatures is greater and the other is less than the inversion temperature.

Process and apparatus for the determination of the inversion temperature

Two frequencies to be compared are applied to two inputs of a flip-flop. output of the flip-flop is fed to a low pass filter and the output of the filter is a saw tooth voltage proportional to the phase difference between the two frequencies. Differentiation of the saw tooth voltage yields a voltage proportional to the difference between the two frequencies. A threshold circuit is provided for sensing the output voltage of the filter to control a flip-flop which in turn reverses the phase of one of the frequency signals and disconnects the output of the differentiator from a capacitive storage circuit.

Frequency comparator

Apparatus for automatically adjusting the frequency of a piezoelectric reator in the form of a bar or plate includes circuitry for applying a voltage to the resonator to cause it to resonate, measuring the frequency of the resonator continuously during a frequency adjusting cycle, continuously comparing the measured frequency with a desired frequency to obtain a difference frequency value, storing the difference frequency value at the beginning of the adjusting cycle, deriving from the difference frequency value a threshold value equal to one-half of the difference frequency value, comparing the threshold value with the frequency difference value, removing material by a sand blast from a first extremity of the resonator as long as the difference frequency value is greater than the threshold value and thereafter removing material from the other extremity of the resonator until the difference frequency value is nil.

Apparatus for automatically adjusting the frequency of piezoelectric

A process for automatically adjusting the frequency of a piezoelectric reator in the form of a bar or plate includes the steps of applying a voltage to the resonator to cause it to resonate, measuring the frequency of the resonator continuously during a frequency adjusting cycle, continuously comparing the measured frequency with a desired frequency to obtain a difference frequency value, storing the difference frequency value at the beginning of the adjusting cycle, deriving from the difference frequency value a threshold value equal to one-half of the difference frequency value, comparing the threshold value with the frequency difference value, removing material by a sand blast from a first extremity of the resonator as long as the difference frequency value is greater than the threshold value and thereafter removing material from the other extremity of the resonator until the difference frequency value is nil.

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Brugg, Switzerland

Hubert Matthey