| 摘要 |
PROBLEM TO BE SOLVED: To obtain the background level for detecting knocking with good accuracy without any increase in sampling speed. SOLUTION: Out of output signals from a pressure sensor S, a signal where no vibration component due to knocking is superimposed is filtered by a band- pass filter 6, and further the output signal of the band-pass filter 6 is filtered by a low-pass filter 10. According to the output signal of the low-pass filter 10, the background level is detected. Sampling for obtaining the background level is performed for a signal passed through the low-pass filter, and in the signal, high frequency component is suppressed for equalization, whereby the background level can be obtained with good accuracy without any increase in sampling speed.
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