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Knock Sensor Waveform Notes
The optimal point at which the High Tension (HT) ignites the Air/Fuel mixture will be just before pinking occurs, it would appear inevitable that at certain times and under certain conditions knock (detonation) will occur.
A knock sensor is fitted to some management systems, the sensor being a small piezo-electrical device that, when coupled with the Electronic Control Modules (ECM), can identify when knock occurs and retard the ignition timing accordingly.
The frequency of knocking (pinking) is approximately 15 KHz. As the response of the sensor is very fast an appropriate time scale must be set, in the case of the example waveform 0-500 ms and a 0-5 volt scale. The best way to test a knock sensor is to remove the knock sensor from the engine and to tap it with a small spanner, the resultant waveform should be similar to the example shown.
NOTE: When refitting the sensor tighten to the correct torque setting as over tightening can damage the sensor.
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