| 摘要 |
PURPOSE:To easily set and adjust reference pulse width on the basis of which a noise is decided by counting noise removal based upon the pulse width from the supply of a pulse signal and inputting the counted value to a comparator when the counted value reaches an expected counted value. CONSTITUTION:A pulse signal (a) is outputted by an engine rotating speed sensor 1 and an FF 21 is set with the normal pulse signal of the signal (a). The FF 21 outputs a high-level signal (b) and a presettable down counter 22 counts down from a preset value according to the signal (b). When the counted value reaches zero, a trigger signal (c) is supplied to the comparator 23, which decides whether or not the level of the signal (a) is lower than a reference level and outputs a high-level signal (d) to a timer 4 when the signal (a) is the normal pulse. The counted value of the timer 4 is supplied to a computing element 5, which computes an engine rotating speed Ne. Then, even when an impulsive noise is mixed with the signal (a), the FF 21 is set, but the noise disappears at the output point of the signal (c), so the noise is removed.
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