| 摘要 |
PURPOSE:To prevent the engine stall beforehand by detecting the carbon contamination in a small quantity by comparing the peak value of the electric signal corresponding to the inductive electric current which is generated in a coil arranged on the periphery of the center electrode of a spark plug with a prescribed value. CONSTITUTION:The inductive electric current generated by the spark electric current which flows in the center electrode of a spark plug 10 which is detected by an electric current detector 200 is introduced into a judging circuit 300 and converted to a voltage by a conversion circuit 301, and the peak value is detected by a peak hold circuit 303. The peak value corresponds to the peak value of the spark electric current which flows in the center electrode on the break down. While, a standard voltage setting circuit 305 adjusts the voltage generated by a constant voltage generator 304 to a standard voltage and outputs said voltage. When the voltage peak value inputted into a comparator 306 is less than the standard voltage, a plus signal is outputted, and a transistor 307 is turned-ON to light up an alarm lamp 310 installed at a driver's seat, and the carbon contamination state of the spark plug 100 is informed to the driver.
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