Knock sensor. Principle of operation and verification
Modern cars are equipped with varioussensors, based on the indications of which the control unit regulates the operation of the whole unit. One of the similar elements involved in the fuel injection system is the detonation sensor, whose operation principle is based on the piezoelectric effect.
Detonation sensor on engine is locatedcar. It generates voltage pulses from detonation explosions in the engine. Based on the readings received from him, the control unit monitors the fuel supply, thereby achieving maximum engine power and fuel economy.
Types of knock sensors
There are two versions of this device -broadband and resonant. But now the resonant knock sensor is no longer installed serially. Also, you should know that they are not interchangeable, so to establish, for example, instead of broadband resonance will not work.
Operating principle
The operation of the sensor is based on the piezoelectric effect. The controller sends a DC signal with a voltage of 5V to the sensor. It has a resistor that reduces the voltage to 2.5V and returns the AC signal to the controller. Transmission of the return signal is carried out along the circuit of obtaining the reference voltage. This is possible due to the fact that the signal from the controller comes in the form of DC voltage, and the reverse signal - AC voltage. When a detonation explosion occurs in the engine, the sensor generates an alternating current signal, the amplitude and frequency of which directly depend on the detonation force. If, during normal operation of the motor, an AC signal with a voltage of 2.5 V is returned to the controller, the controller leaves the engine running in the current mode. If the received signal has deviations from the set value, the controller changes the ignition timing to stop the detonation and to switch the engine operation to the economical and safe mode.
Checking the knock sensor