GB1127568A - Flowmeters - Google Patents

Abstract

1,127,568. Flowmeters. FORD MOTOR CO. Ltd. June 1, 1967, No.25333/67. Heading G1N. The rate of flow of fluid through a conduit is determined by measuring the change in temperature as it flows over the cold junction of a Peltier thermo-electric device. As shown (Fig. 1) a conduit 1 carrying a fluid is part surrounded by a group of sintered bismuth telluride thermoelectric elements 2 connected electrically in series and thermally in parallel, energized by a controller 4, whereby the upstream end 2a of the element assembly is a cold junction, and end 2b a hot junction. The temperatures before, at and after the junction are measured electrically at 5, 7 and 6 respectively. Thermometer 7 controls unit 4 to maintain a constant temperature at the cold junction 2a. The difference between the upstream and downstream temperatures is determined at 8 and modified at 9 in accordance with the upstream and cold junction temperatures to give a signal at 10 indicative of the fluid flow. In a modification the controller 4 supplies a constant current to the Peltier unit, instead of maintaining the cold junction at a constant temperature. In another embodiment (Fig. 2), the temperature difference across the Peltier unit 2 is maintained at a constant value by controller 12 and amplifier 11 feeding the unit 2. Automatic compensation for variations in the initial fluid temperature is produced by a temperature-sensitive resistor 15 in series with the output from amplifier 11.