| 摘要 |
An engine knock sensor for sensing knocking occurring in an internal combustion engine. The vibration in the engine, involving the vibration component caused by the knocking, is sensed by a vibration sensor. A feed back control is achieved by a closed loop constituted by a variable-gain amplifier the gain of which is controllable and adapted for amplifting the electric signal from the vibration sensor corresponding to the vibration, a mean level detecting circuit for calculating the mean value of the level of the amplified signal and outputting a mean level signal, and a gain controller for effecting a control of the gain of the variable-gain amplifier in accordance with the mean level signal so as to maintain the level of the amplified signal above a predetermined level. A predetermined voltage is added to the mean level signal to produce a reference signal which is compared by a comparator with the amplified signal from the variable-gain amplifier. A knocking signal is produced when the level of the amplified signal exceeds the level of the reference signal.
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