CIRCUIT ARRANGEMENT FOR ADAPTING AN ACTIVE SENSOR TO AN EVALUATION CIRCUIT

摘要

A circuit arrangement is disclosed which permits connection of an active sensor (1) in the form of a binary current source to an electronic evaluation circuit (3) designed for use with a passive sensor. The electronic evaluation circuit (3) comprises a comparator (4) which produces a signal proportional to the speed (revs.) and a window comparator (6, 7) with which the functioning of the sensor (1) can be monitored. The voltage signal applied to the comparator (4) is produced by a resistor (R1) connected in series with the active sensor (1) and with a voltage divider (R2, R3) which is connected in parallel with the active sensor. The voltage signal is led to the N input of the comparator (4) via an RC element (R4, C1) and to the P input of the comparator (4) directly, thus ensuring that the comparator responds to fluctuations at the central tap (M) of the voltage divider. This circuit is not sensitive to fluctuations in the intensity or voltage of the supply current or to drift in the active sensor.