GB1359574A - Temperature sensors - Google Patents

Abstract

1359574 Temperature alarms S DAVALL & SONS Ltd R W G SOMERVELL and E BENNETT 31 Jan 1973 [9 Feb 1972] 6130/72 Heading G4N [Also in Division G1] A temperature sensor comprises a magnet 2 on a rotary member 1 and producing a magnetic flux; a ferromagnetic polepiece element 4 of which the permeability varies with temperature in thermal communication with the member and arranged to alter the flux in response to the temperature of the member; a pick-up coil 3, stationary with respect to the rotational axis of the member and sensing the flux as the magnet passes the pick-up; and an integrating circuit 5 arranged to receive signals from the pick-up representative of the rate of change of the flux magnitude and to integrate the signals to produce an output signal representative of the temperature of the member. The material of the polepiece 4 exhibits a loss of permeability with temperature, for example when heated through a 10‹ C. range near its Curie point reduces the transmitted flux by a factor of 3. In an alternative embodiment, Fig. 2 (not shown), the polepiece (4<SP>1</SP>) is in the form of a shunt or keeper across the magnet poles to inhibit the flux produced by the magnet until the keeper temperature reaches the Curie point. The keeper material linearly reduces transmitted flux by a factor of 3 over a range of temperature from 10‹ to 220‹ C.