GB669865A - Electrical indicating or recording instruments - Google Patents

Abstract

669,865. Frequency measurement. CHAMBERLAIN & HOOKHAM, Ltd., and DEACON, L. O. July 4, 1950 [July 27, 1949], No. 19721/49. Class 37. In a device (Fig. 1) for indicating the number of incoming electrical impulses per unit time, e.g. from a power station load measuring instrument, a shaft r is stepped by a ratchet and pawl a, t, electromagnetically operated by the impulses to rotate a cam v, which alternately closes one pair of contacts w during each half revolution. Electromagnets m are thus energized to alternately connect each of the two clocks j to rotate an associated spring-loaded gear-wheel f freely mounted on a spindle a carrying an indicating pointer c which is in turn rotated against its return spring b by arms h engageable by projections g carried by the wheels, and released twice per revolution on the disengagement of a pawl o from a ratchet n by the momentary energization of an electromagnet p through the contacts y closed by the cam x on the shaft r. If, e.g. 30 impulses rotate the shaft by one half revolution, the spindle a is alternately turned by each clock through an angle proportional to the time during which the impulses are received, and allowed to return to its starting point, so that the scale d and the pointer a may be calibrated to indicate the frequency per minute based on the last, e.g. 30 impulses received. In a modification, Fig. 2 (not shown), an additional cam on the shaft r operates contacts to alternately start and stop the clocks in addition to their engagement and disengagement.