GB815116A - Improvements in moving-indicator measuring or indicating instruments - Google Patents

Abstract

815,116. Photo-electric instrument monitoring. BECKETT & PARKER Ltd. April 23, 1957 [May 3, 1956], No. 13635/56. Class 40 (3). A shutter attached at an intermediate position to and forward of the plane of an instrument needle interrupts light incident upon a light-sensitive cell, the light source and cell being on a common mounting rotatable around the axis of the needle. A strip of foil 16, Fig. 2, fastened to an ammeter needle 2 interrupts the light of a lamp 9 falling on a transistor 5. Lamp 9 and transistor 5 are mounted on a pivot 7 and clamped by a nut 13, their position being indicated by a finger 15. The transistor 5 is connected to an amplifier and a relay or trigger circuit to operate a cut-out device when the current in the ammeter exceeds a certain value. The photo-cell 5, Fig. 5, and illuminating lamp 9 may instead be coupled to a shaft 21 operated by reduction gearing 22 driven by motor 23, which. in turn is controlled by the output of the photocell, a signal from which stops the motor 23 so long as the position of coincidence is maintained. When it is disturbed the cell and lamp are again allowed to scan across the path of the needle 2. A belt and pulley power take-off 25 operates the arm of the potentiometer 26, the voltage across which is fed to voltmeters R which serve as repeaters.