Patent GB-789541-A (GB)
Title: Improvements in or relating to electrical telemetering systems
IPC: G01R17/08
Filed: 1954-11-15
Abstract: 789,541. Electric telemetering systems. GENERAL ELECTRIC CO., Ltd., BONHOMME, V. G., and BEESLEY; J. H. Nov. 7, 1955 [Nov. 15, 1954], No. 33035/54. Class 40 (1). In a telemetering system of the type described in Specification 694,907, wherein a torque is applied to an electric meter movement in accordance with the magnitude of a variable quantity to be measured and as a result of a coding sequence, is balanced by a counter-torque whose value is determined by the condition of a plurality of electromagnetic relays, means is provided which prevents a new coding sequence from being initiated unless a significant change has occurred in the magnitude of the said quantity. As shown, the meter movement 8 carries an operating winding 9, the current through which represents the quantity whose magnitude is to be transmitted, a balance winding 10, and a contact arm 12. When there is no current flowing in windings 9 or 10 the contact arm is just in engagement with the right-hand contact 12. The current through the coil 10 is determined by resistors 1 to 7 which are controlled by relays A to F, the values of the resistors being.so chosen that when relay A operates the current through winding 10 is <SP>32</SP>/ 63  of the amount required to balance the torque that is applied. to the meter movement when the quantity to be transmitted is at its maximum value. Similarly the values of resistors 2 to 6 are chosen for currents of <SP>16</SP>/ 63'  8 /33 ,... 1/ 63 ,respectively, and the value of resistor 7 for 1/ 63 . A resistance 18, having a value equal to that of the winding 10, ensures that the load on the power supply connected between terminal 13 and earth remains substantially constant. In operation, a plurality of relays P to X (not shown) are operated one at a time in alphabetical order. If the torques are unbalanced, arm 11 is in engagement with one of the contacts 12, and operation of relay P causes contact P1 to complete an energizing circuit for relay J. On relay J operating, contacts J1 prepare circuits between terminal 13 and earth by way of one of the resistors 1 to 6 and winding 10, contacts J2 prepare operating circuits for relays A to F, contacts J3 complete a holding circuit for relay J, contacts J4 break the holding circuit for any of relays A to F which were operated during the preceding coding sequence, and contacts J5 open and disconnect resistor 7 from the coil 10. The contact arm 11 will thus move into engagement with the right-hand contact 12 if not already there. After a predetermined interval P releases and Q operates, and contacts P2 prepare an operating and holding circuit for relays A to F, contacts Q1 complete a circuit for relay A, which is slow to operate, and contacts Q2 connect resistor 1 to the winding 10. If the current through winding 10 is not greater than that required to effect balance, the arm 11 remains in engagement with the right-hand contact 12 and maintains the circuit of relay A, and contacts Al complete an alternative circuit from resistor 1 to winding 10, contacts A2 completing a holding circuit for relay A. Relay Q releases and R operates, contacts R1 completing an energizing circuit for slow-to-operate relay B and contacts R2 connecting resistor 2 to the winding 10. If the current through winding 10 is not greater than that necessary to effect balance the arm 11 remains in engagement with the right hand contact 12 and maintains relay B operated. Assuming that the current is greater than that required for balance, the arm 11 engages with the left hand contact 12 and breaks the circuit of relay B, thus preventing its operation. On relay R releasing, R2 disconnects resistor 2 from the winding 10, the arm 11 moves into engagement with the right hand contact 12 ready for the operation of relay S, and the balancing process continues, the appropriate relays A to F remaining operated. At the end of the balance sequence the arm 11 will be in engagement with the right-hand contact 12, and to prevent the initiation of another coding sequence irrespective of whether or not the magnitude of the variable quantity has changed, the operation of relay X releases relay J and contacts J5 connect resistor 7 to the winding 10 to supply a current increment just sufficient to move the arm 11 to a neutral position. The relay J is thus prevented from operating on the operation of relay P until there is a change in the current to the winding 9. The relays A to F are provided with further contacts (not shown) by which the conditions of these contacts are transmitted to a control station. The balancing process may be carried out by reducing the current in diminishing steps instead of increasing it. The variable quantity may be applied to a measuring device, e.g. a pressure gauge, a suitable mechanical coupling being provided between the measuring device and the meter movement to apply a torque in accordance with the variable quantity.