System for non-contact determination of angle of rotation of rotatable element for e.g. ignition control in motor vehicle

摘要

The angle determination system includes an evaluation circuit designed so that two sensor elements disposed in a B-field are supplied respectively with AC current shifted in phase by 90 deg or corresp. AC voltages, which are formed as follows: I1(t) = IO. cos(w.t) and I2(t) = I0.sin(w.t), so that the voltages (UH1,UH2) result at the outputs of the sensor elements as follows : UH1(t,alpha) = C1.B1.cos(K alpha ).I1(t) and UH2(t, alpha ) = C2.B2.sin(K alpha ).I2(t), where the constants are such that C1 = C2 = C and the field components are such that B1 = B2 = B.The sum of the two voltages (UH1(t),UH2(t)) is formed in a summation circuit (23). The original AC current and the output signal of the summation circuit are processed in a phase comparator (25) in such a manner, that an output voltage (UA) results, proportional to the angle of rotation ( alpha ).