| 摘要 |
An apparatus for determining combustion condition of engine detects ion current flowing in a spark plug. The apparatus samples the ion current by carrying out A/D conversion at every constant time period. The apparatus stores a maximum value of A/D converted values as a peak hold value. The apparatus further detects and stores that the ion current traverses a reference voltage during the A/D conversion time period. The apparatus clears the peak hold value, if the ion current traverses the reference voltage. The apparatus determines the combustion condition based on the peak hold value which has not been cleared continuously over a predetermined number of times of the A/D conversion. It is possible to reduce influence of noise.
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