Detonation sensors are used to detect irregular vibration of the engine caused by uneven combustion. As a rule, there are two approaches to the use of engine detonation sensor: Vibration detection and pressure measurement.
Most detonation sensors act on the basis of the first method. Vibration detection sensors can be divided into three types depending on their sensitive mechanisms: inductive resonance sensors, piezoelectric resonance sensors, as well as piezoelectric non -resonant sensors. Both inductive and piezoelectric resonance sensors consist of a vibration plate, which has the same resonant frequency as the vibration of detonation. When detonation occurs, the plate reaches the maximum amplitude of the oscillations, which is converted into an electrical signal using an electromagnetic inductive effect or piezoelectric effect. Resonance sensors can only detect a certain frequency of engine detonation due to their characteristics of a narrow-band response. On the other hand, the piezoelectric non -resonant type uses the spring -loaded mass of the system to measure vibration directly and, thus, has a wider frequency strip (usually from about 5 kHz – 15 kHz). Since the frequency of detonation can differ slightly with the engine speed, non -resonant sensors, as a rule, work better than resonant. Vibration detonation sensors are usually installed on the engine block or cylinder block head.
Another way to detect detonation in the engine is to measure the cylinder directly internal pressure. Pressure sensors, as a rule, are integrated into the spark plugs by installing the ring -shaped piezoelectric element to the puck. When engine detonation occurs, high -frequency noise is generated and applied to the normal shape of the combustion pressure signal. Detection detonation is achieved by filtering this signal.