GB1033824A - Improvements in devices for checking the accuracy of watches, clocks and like timepieces - Google Patents

Abstract

1,033,824. Testing timepieces. ALTAIR ELECTRONICS Ltd. Oct. 26, 1962 [July 26, 1961], No.27120/61. Heading G3T. A device for checking the accuracy of a timepiece comprises a mechanical resonator, means responsive to the tick of the timepiece to apply a a series of impulses to the resonator at a frequency equal to the tick frequency or a sub-harmonic thereof, and means for determining the amplitude of vibration set up in the resonator. A piezoelectric transducer 10 or microphone, Fig. 1 (not shown) converts the ticking, e.g. at 1/ 5 sec. intervals, into a signal applied to an amplifier 11 such as a three-stage transistor amplifier having variable gain under manual control. The amplified signals A, Fig. 2 (not shown), are applied to the triggering input of a blocking oscillator 12 which has a relaxation time B, Fig. 2, somewhat greater than that between two consecutive ticks at the nominal rate. Thus each alternate signal becomes a short rectangular positive going pulse, e.g. of four milliseconds as at P(G). The negative going overshoot of the pulse is clipped by a germanium diode 13 shunted across the blocking oscillator with a resistor 14, the resultant output being fed to a solenoid 15 which excites a mechanical resonator or reed 17 resonant at 30 c/s. Co-operating with the reed is an inductance 18 in the circuit of a transistor oscillator 19 arranged to generate an output frequency which is high compared with the resonator frequency, e.g. 50 Ko/sec,and so that this output is modulated at the reed frequency to a depth dependent on the amplitude of the reed. The modulated oscillation is fed through demodulating and filtering means 20 to extract the reed frequency component which is applied to a frequency selective amplifier 21 tuned to 30 c/s, the output being fed to a visual indicator or A.C. pointer type instrument 22. A discriminator circuit may be provided in the output from the demodulator 20 to identify the sign of the error of the timepiece. This error is corrected by adjusting the timepiece regulator until the resonator amplitude is maintained at a steady value for a few seconds. The device will cope with the usual tick frequencies of 2, 4, 5, or 6 per sec. which are sub-harmonics of the reed frequency, provided that the reed has a decrement value of several seconds.