Method of and apparatus for ascertaining the fine position value of a movable body

A method of ascertaining a fine position value z describing the instantaneous absolute position of a movable body by means of a position sensor which includes a stationary sensor unit (7) and an exciter unit which moves with the body and which can pass through a predetermined range of movement comprising at least one measuring segment, wherein the sensor unit (7) delivers a plurality of output signals which jointly, at least within a measuring segment reproducibly, and definitely describe a fine position value z and wherein in the measuring mode the values of signals derived from the output signals are compared in a computing unit (10) to reference values stored in a comparative value memory (14),

• characterized in that
• in a calibration mode of the position sensor in which the exciter unit is in a defined relationship with respect to a calibration unit (31) and passes through its range of movement at least once amplitude value groups ΔaE(z), ΔbE(z), . . . are successively simultaneously taken off from the output signals aE(z(t)), bE(z(t)), . . . of the sensor unit (7), from which amplitude value groups there are formed groups of separate average values AE(z), BE(z), . . . , which respectively implicitly contain the associated true fine position value z as an unknown quantity and are fed to the calibration unit (31) which converts same using the calibration fine position values μ(z) which are known thereto and which are correlated in defined relationship with the fine position values z(AE, BE, . . . ) into genuine reference values AE(μ(z)), BE(μ(z)), . . . and stores them with the associated known fine position value μ(AE, BE, . . . ) respectively as associated values multiplets in the comparative value memory (14), and
• in the measuring mode for each current fine position value z to be ascertained amplitude value groups ΔaM(z), ΔbM(z), . . . are successively simultaneously taken off from the output signals aM(z(t)), bM(z(t)), . . . identifying it of the sensor unit (7) and from which amplitude value groups there are formed groups of separate average values as measuring values AM(z), BM(z), . . . , from which then the current fine position value z(AM, BM, . . . )=m μ(AE, BE, . . . ) is ascertained in the computing unit (10) by means of the genuine reference values AE(μ(z)), BE(μ(z)), . . . stored in the comparative value memory (14) and the associated known fine position value μ(AE, BE, . . . ), in that the difference of the cross products from the reference values of a group and the measuring values of a group going towards zero.