Temperature compensation of a linear sensor

Claim 1

Method of temperature-compensating a sensor having, at any given temperature within a range of temperature suitable for use of the sensor, a straight characteristic line giving the relation between sensor output (7) and a physical property variable (P) measured by said sensor, said characteristic line having a slope (k) which has a first temperature coefficient (TK k ) and defining, for a predetermined value of said physical variable, a reference value (U off ) of sensor output which reference value has a second temperature coefficient (TK off ), said method depending upon the discovery that the respective characteristic lines of said sensor for various temperatures commonly cross in a point (14), said method comprising the steps of: determining, from preliminary measurements of known magnitudes at not less than two different sensor temperatures the coordinates (U 0 , P 0 ) of said point (14) representing a value of said physical variable for which the sensor output does not vary with temperature, and providing said coordinates and also said first and second temperature coefficients (TK k ,TK off ) as sensor constants to a microcomputer (20); calculating the slope (k 0 ) of the sensor characteristic at a reference temperature (T 0 ) from said preliminary measurements and providing its value as a sensor constant to said microcomputer; continually measuring the sensor temperature (T) and furnishing its value as an operating variable to said microcomputer; continually furnishing said sensor signal (U.sub.(P,T)) to said microcomputer for derivation of said physical variable (P.sub.(T)); deriving a value of said physical variable (P.sub.(T)) from said sensor signal (U.sub.(P,T) and from the determined sensor temperature (T) by computation in said microprocessor in accordance with the relation: P.sub.(T) =P.sub.0 +(U.sub.(P,T) -U.sub.0)/k.sub.0 (1+TK.sub.k ΔT) in which P 0 and U 0 are said coordinates of said point, U.sub.(P,T) is the sensor signal, k 0 is said slope for the sensor characteristic at said reference temperature, ΔT is the difference (T-T 0 ) between the determined sensor temperature (T) and the said reference temperature T 0 and TK k is the temperature coefficient of the sensor characteristic slope at said sensor temperature.