| 摘要 |
PURPOSE:To prevent incorrect waveform shaping signal caused by electric noises by temporarily stopping comparison operation of a waveform shaping circuit if it executes such operations as to cause electric noises while a crank angle signal remains in the vicinity of a reference level. CONSTITUTION:While spark discharge is generated at an ignition plug, and a crank angle signal remains in the vicinity of the rising reference level Rd, a masking indication signal is sent to an input terminal of a mono-stable multivibrator 62 just before the time tb, and a pulse having a very small width is produced from an output terminal of the vibrator 62, and a condenser 66 is instantly charged by a constant current source 68 and is then discharged through resistors 70, 72 and diodes 74, 76. But, as, during the discharge, the crank angle signal becomes sufficiently larger than a reference level from a waveform shaping circuit 53, the waveform shaping signal is maintained at 0 during the discharge, and no incorrect pulse will occur in the waveform shaping signal in spite of the noise factor. |
