GB946203A - Improvements in and relating to apparatus for calibrating and adjusting rotating disc electricity meters - Google Patents

Abstract

946,203. Testing electricity meters. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. April 19,1960 [Jan. 28, 1959], No. 3102/59. Heading G1U. An apparatus for calibrating and adjusting rotating disc electricity meters comprises a member 1 rotating at a reference speed determined by the rotation of a reference meter under a given load, the member being arranged to direct or obscure repeatedly at regular intervals during each revolution a ray L from a light source 6 to a light sensitive device 8; an electronic counting circuit 16 connected to count the signals from the said device; a second member 2 rotating at a speed determined by the rotation of a meter under test the load of which is fixedly related to the first load, the second member being arranged to direct or obscure at one position 5 of the second member in each of its revolutions a ray R1 from a light source 11 to a second light sensitive device 14, and a gating circuit 9 controlled by the signals from the second device and controlling the counting circuit to start and to stop by successive signals the operation of the counting circuit. An electric motor RM is connected so as to adjust by its rotation an adjustable element in the meter under test, and a switching arrangement CU connects the motor to a supply source in accordance with signals derived from the result of the counting operation, so that the motor is energized to adjust the meter so as to reduce its error to a predetermined tolerance in accordance with the error detected by the counting circuit. The light sensitive devices 8 and 14 may be photo-cells or phototransistors and the outputs from these are passed through amplifier and wave shaper stages 10 or 15 before being applied to the gate 9. The disc 1 is provided with peripheral slits 3, of which there may be for example 200, so that errors in the speed of rotation of the meter under test exceeding ¢% may be detected in one revolution. The accuracy of the system may be improved by including a circuit RS between the stage 15 and the gate 9 which arranges that the gate 9 may be held open for more than one revolution of the disc 2. In the counter 16 digital display tubes may be used, and the cathode resistors of these tubes are connected to the contacts of a switch GS. When the gate 9 closes, the control unit CU is energized so as to set the motor RM into motion, thus driving the wiper WP of the switch GS through the clutch CL and also the adjustments of the meters under test through the clutch selector unit. The switch GS has potentials at its contacts set up according to the digital count set up by the meter under test, and when these potentials have been fully interpreted by the control unit CU and found to agree with the required count the motor RM is stopped and the clutches disengaged. The wiper WP is then returned to its rest position. The rate of rotation of the reference disc 1 may be checked against a standard clock SC by operating the switch SO.