Circuit arrangement to detect signals indicating a change in current through a needle lift sensor of an injection nozzle in combustion engines, which is connected to a constant direct voltage supply

摘要

A circuit arrangement to detect signals indicating a change in the current of a needle lift sensor of an injection nozzle in combustion engines, which is connected to a constant direct current supply.P PThis circuit arrangement, which is intended to detect the signals indicating a change in current that are emitted by a needle lift sensor Z.sub.s of an injection nozzle in combustion engines that is connected to a direct current source, is designed in such a way that it will also detect minor signals indicating a change in current under the conditions prevailing in motor vehicles, which exhibit a high level of interference. For this purpose, the sensor (Z.sub.s) is connected to the controlled outlet (4) of a controlled direct current source (1) and a sensing resistor (R.sub.M) is connected between the outlet (3) of the regulating amplifier (2) and the outlet of the direct current source (1); the outlet (3) of the regulating amplifier (2) is connected to the input of an AC amplifier (5) with band-pass characteristics, and the outlet of the AC amplifier (5) is connected to the input of a Schmitt trigger (7), the output signal (U.sub.A) of which represents the changes in the sensor current (I.sub.s).