GB1450464A - Temperature compensated electronic timepiece - Google Patents

Abstract

1450464 Electronic timepieces CITIZEN WATCH CO Ltd 4 Feb 1974 04945/74 Heading G3T In an electronic timepiece comprising a reference oscillator 1, e.g. a crystal oscillator, a frequency divider 2, a counter 3 and a display mechanism 4, the frequency of the oscillator 1 is compensated for variation with temperature by circuitry 5 including a temperature detector 6 which delivers a signal when the temperature exceeds a predetermined level. Preferably the device 6 is a transistor (Tr1) Fig. 5 (not shown) or a diode (D 3 ) Fig. 10 (not shown) e.g. a Schottky diode, and a voltage is applied thereto which, at the predetermined temperature, is the devices threshold voltage, so that when this temperature is reached a digital output signal is changed. To the detector 6 may be connected a buffer amplifier and a constant voltage circuit Figs. 6-9 (not shown). The temperature compensating circuitry 5 futher comprises a voltage generator 9, Figs. 16, 17, which, under the control of a coded signal generator 10 e.g. a shift register, applies a voltage to the temperature detector 6. The digital output signal of detector 6 is fed to a signal discriminator 11. In the embodiment of Fig. 16 the output of discriminator 11 is fed to logic circuitry 12 which adds extra pulses to the input to divider 2 from oscillator 1. In the embodiment of Figs. 3, 17 the discriminator output is fed to switch circuitry TG1-4 which stabilizes oscillator 1 against frequency variation with temperature by selectively switching in capacitors in parallel with the oscillator. The device 5 may contain a plurality of detectors (6a-d) Fig. 11 (not shown) the respective digital outputs of which change at different temperatures. By feeding the outputs through logic circuitry (7) the frequency-temperature characteristic of the oscillator 1 is corrected a plurality of times withing a given temperature range Fig. 12 (not shown). In the embodiment of Fig. 13, the base electrodes of a plurality of transistors are connected via resistors R b1 -R Bn to respective sliders which engage a common potentiometer Ro. Alternatively the connections to Ro may be fixed, Fig. 14 (not shown). In either case part of Ro may be variable or replaceable to enable the embodiments to be used with oscillators having different frequency temperature characterization.