Patent GB-663083-A (GB)
Title: Improvements in apparatus for measuring a function of plural variable conditions
IPC: G01F1/50
Filed: 1948-07-30
Abstract: 663,083. Electric indicating systems. BAILEY METERS & CONTROLS, Ltd. July 30, 1948. [Aug. 2, 1947] No. 20322/48. Class 40 (i) [Also in Group XXXVI] Apparatus for measuring a function of plural variable conditions comprises a balanceable network arranged to develop an output voltage variable with changes in one or more conditions which is energised by an A.C. voltage variable with changes in another condition, and adjustable A.C. energised means developing a counter voltage in opposition to the output voltage which is automatically regulated to equality therewith by means responsive to the difference between the voltages. In Fig. 1 a resistance bridge 26 comprises a zero-set potentiometer 6 and temperature variable arms 27, 28 in a fluid conduit 29 on opposite sides of a heat exchanger, and is A.C. energised from the equal opposed secondaries of a transformer having a core member 34 which is movable by a float 35 responsive to the differential pressure across an orifice 36 in the conduit. The unbalance voltage is applied to an amplifier and motor control device 20 in opposition to a counter voltage from an A.C. energised potentiometer 41 adjustable by the controlled motor 21 to equalise the voltages. The bridge input voltage is proportional to the rate of fluid flow and the unbalance voltage to the differential temperature across the heat exchanger, so that the equilibrium counter voltage shown by an indicator 23 driven by the motor is proportional to the rate of heat transfer in the exchanger. In Fig. 3 the bridge 64, unbalanced by variations of the resistance arm 82 by fluid pressure in a conduit 84, is energised from the equal opposed secondaries of a transformer having a core member 86, movable in response to the differential pressure across an orifice 89 in the conduit, and the bridge 65, unbalanced by variations of the resistance arm 85 by the temperature in the conduit, is energised from a similar transformer having a core member 90 adjustable by a motor 21 driving an indicator 23. The bridge unbalance voltages are applied in opposition to the control device 20, and the motor repositions the core member to equilibrate the bridge outputs so that the input voltage to the bridge 65 is proportional directly to the pressure and flow, and inversely to the temperature in the conduit, and the indicator registers the conduit power flow. In a further modification, Fig. 2 (not shown), the bridge inputs are varied by temperature or pressure controlled potentiometers while the unbalance voltages to be compared are derived from manually and motor driven potentiometers across the respective bridge outputs. The Specification as open to inspection under Sect. 91 comprises also modifications in which an A.C. energised resistance bridge is unbalanced by variation of an arm responsive to an unknown condition to produce an unbalance voltage applied to a motor control device in opposition to a counter voltage from a potentiometer readjusted by the motor until the voltages are equal; in which the outputs of two bridges unbalanced by unknowns are added and balanced against a voltage from a motor driven potentiometer controlled by the total unbalance voltage, and in which the opposite arms of one bridge are varied from balance in response to strain, while the other bridge comprises two parallel potentiometers which are respectively manually and motor driven to restore voltage balance. This subjectmatter does not appear in the Specification as accepted.