GB819136A - Photo-electric calibrating and testing instrument for electricity meters - Google Patents

Abstract

819,136. Testing and calibrating meters. LANDIS & GYR A.G. June 21, 1955 [June 23, 1954], No. 17968/55. Class 37. [Also in Groups XL (b) and XL (c)] In a system for testing and calibrating electricity meters against a standard meter, each meter, with the aid of a photo-cell, produces impulses having a recurrence frequency depending on the speed of its rotor and one set of impulses controls the rectilinear or circular time base of a C.R.O. and the other deflects or modulates the beam. Rectilinear trace, Fig. 1. In this system impulses from photo-cell F1 after amplification are applied to the deflector plates P1. Impulses from F2 discharge, with the aid of a gas filled triode V5, a capacitor C18 which between impulses is charged via a constant current pentode V6 to provide the horizontal sweep. voltage. To compensate for the fact that the voltage reached between discharge impulses depends on the speed, the bias on pentode V6 is automatically adjusted to resist any change in the maximum voltage at point 1. Changes at this point are transferred via the cathode follower triode section of valve V7 to the diode section which at a given voltage begins to conduct, discharging capacitor C19. The resulting change in the charging current of C19 modifies the bias of V6 appropriately. System with circular trace, Fig. 2. In this case the impulses from cell F1 control the beam intensity. Impulses from the other cell produce with the aid of an R.C. network quadrature alternating voltages which are applied to the deflector plates to produce a circular trace. Phase splitting network, Fig. 2. It is stated that if R1.C1=R2.C2=R3.C3 and R1: R2: R3 =1:6:3 and if R4.C4=R5.C5=R6.C6 and R4 : R5 : R6=1: 6: 3 then the phase difference between the voltages at A and B is independent of frequency and is proportional to loge R1.C1/R4.C4.