Patent GB-567580-A (GB)
Title: Electric measuring systems
IPC: G01R17/04
Filed: 1943-05-25
Abstract: 567,580. Electric indicating and controlling systems. KEINATH, G. May 25, 1943, No. 8335. Convention date, July 23, 1942. [Class 40 (i)] [Also in Group XXXVI] A system for measuring, indicating, or control purposes in which a movable pointer, recording device, or control element operates in a given relation to changes of a variable magnitude such as voltage, current, power, speed, pressure, temperature, flow quantity, efficiency, &c., so controls the operation of a device that the timeintegrated performance of the latter is dependent upon the magnitude of a condition under observation. Fig. 1 shows a system for measuring current in an A.C. line 101. A differential relay has a movable armature 125 and two actuating coils 121, 128, of which the former is connected to a current transformer 111. The resistor 131 of a potentiometer is energized by constant voltage from the line 101 over a voltage-stabilizing resistor or lamp 133. The movable contact 132 and one end of the resistor 131 are connected to the relay coil 128, the current through which consequently depends on the position of the contact 132. This is driven from a synchronous or other constant speed motor 153 and is arranged to reciprocate over a given range so that the voltage applied to the coil 128 varies cyclically. A circuit 181 connected to the relay contacts 126, 127 is energized from the line 101 or from a D.C. source or condenser circuit and contains a recorder 141, an integrating counting device 145, and an indicator 149. The recorder 141 has a cylinder co-operating with a stylus 142 moving with the contact 132, the stylus and cylinder forming two electrodes between which passes a recording tape 144. A line is marked on this tape extending over that portion of travel of the stylus during which the circuit 181 is closed by the relay, i.e. until the voltage applied to the coil 128 is such that the coils 121, 128 balance and the relay opens. The length of each line is proportional to the current acting on the transformer 111, and in a series of consecutive cycles of operation a number of parallel lines are marked on the tape 144, giving a record of current variations in a given time. The counting device 145 contains an integrating counting mechanism 146 operated in synchronism with the drive motor 153, as by a synchronous motor 147 fed from the line 101. The operation of the counting device begins and ends within each cycle simultaneously with the recording operation, so that the amount registered during each cycle is a measure of current. As this registration is cumulative, the reading indicates ampere-hours if the frequency is constant. If the line voltage is constant the reading indicates kilowatt-hours. The indicator 149 is a clockwork mechanism operated by a synchronous motor. At the end of each operating cycle the pointer shows the magnitude of the current then measured. After the completion of the cycle the pointer either returns to zero or maintains its position until corrected at the end of the next cycle. If the integrating operation of the counter 145 is extended over a definitely limited number of cycles it operates as a maximum demand meter. Flow of steam through a pipe may be similarly measured by means of a manometric device responsive to the difference between the pressure on opposite sides of an orifice plate. This influences the relay instead of the coil 121 and transformer 111, by direct connection to the movable relay contact 125. As the differential pressure measured by the pressure gauge is proportional to the square of the rate of flow, the opposing force due to the coil 128 is made proportional to the square of the current by using an unsaturated iron plunger. Alternatively the relay may control a reversible drive motor for the potentiometer contact, so that this is automatically brought to the point of balance. The counting device has a wattmetric driving motor, the voltage coil being connected to a constant voltage source and the current coil being in series with the relay coil 128. The system shown in Fig. 4 determines the quantity of heat consumed between two measuring points of a conduit containing a fluid heat-carrier such as water. Heated water flows into the system through the conduit 402, passes through heat-consuming apparatus, and leaves by the conduit 403. Thermo-responsive resistors 419, 420 are arranged in the conduits 402, 403 and are connected to a potentiometer resistor 431 so as to form a balanceable circuit fed from a constant voltage source 484. The zero branch is connected to the movable contact 432 and contains the actuating coil 428 of a polarized relay whose movable contact controls the circuit 481 of an integrating counting device 445. The drive motor 447 of this counting device is fed from an A.C. line 401 and operates the counter proportionally to time. Another synchronous motor 453, also fed from the line 401, drives the potentiometer contact 432 cyclically so that the voltage in the zero branch of the measuring circuit passes periodically through zero. As this position is passed the relay closes the circuit of the counter 445 which operates at uniform speed until the potentiometer contact reaches the end of its travel so that the valve counted during each cycle is a measure of the temperature difference between the resistors 419, 420. In series with the synchronous motor 453 is a contactor 463 actuated by a cam 462. This is connected with a metering mechanism 461 for metering the flow of water so that the contactor 463 is opened and closed at intervals depending on the rate of flow. The individual contact periods are arranged to be at least equal to, and preferably longer than, the duration of a complete cycle of the potentiometric variation effected by the contact 432. The counted value is the product of the two factors, temperature difference and rate of flow and consequently is proportional to the quantity of heat consumed. Fig. 6 shows an arrangement for measuring the energy transmitted by a shaft 604. Two inductance coils 619, 620 are varied oppositely in accordance with the angular deflection of a section II of the shaft with respect to a section I and form two arms of a bridge, the other two arms being formed by a potentiometer resistor 631. The slider 632 is connected in the zero branch of the bridge in series with the actuating coil 628 of a relay which controls the operation of a time-proportional counter 645. This may be driven by a synchronous motor or by clockwork. The slider 632 is driven by a synchronous motor 663 controlled by a contactor 663, which is operated by a cam 662 driven by gearing 664, 665 from the shaft 604. The gearing is so arranged that a contact is made after a given number of revolutions, lasting each time for a period of sufficient duration to permit the motor 653 to perform a complete cycle of operation. The counter 645 measures the product of the torque and the number of revolutions and may be calibrated in horsepower-hours. In a modification the motor 653 is controlled by a timing device so as to operate intermittently at equal time intervals and the counter 645 is driven by a generator coupled to the shaft 604 so that its frequency, and hence the synchronous speed of the counter, is proportional to the speed of revolution. The counter measures the product of torque and speed and may be calibrated in horse-power. Alternatively the counter may be driven directly from the shaft. Efficiency may be measured by the arrangement shown in Fig. 9 the measurement being in terms of H.P.-hours per unit of fuel consumption. A measuring circuit 983, containing two torque-responsive elements 919, 920 and a potentiometric resistor 931 whose slider 932 is operated by a synchronous motor 953, controls the coil 928 of a relay so as to transform the torque of a shaft 904 into a corresponding length of time to be indicated on a recording tape 944 by a stylus 942 driven by a synchronous motor 975. The drive motor 953 of the potentiometer is controlled by a contactor 963 operated by a cam 962 so as to energize the motor in intervals depending on the speed of revolution of the shaft. The motor 975 in addition to being controlled by the torque-responsive relay, is also controlled by a contactor 973 actuated by a cam 972 from a metering device 971 measuring the rate of flow in a fuel supply conduit 903.