| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus for determining the inter-electrode gap of a spark plug 6 capable of automatically measuring the inter-electrode gap without requiring a special jig, and being usable even after being fastened to an engine body. SOLUTION: A measuring portion 11 is provided for measuring the discharge time T of a counter electromotive force which is generated on the primary side 4a of an ignition coil 4 for the spark plug 6 upon discharge of the spark plug 6. A predetermined relationship between the inter-electrode gap A of the spark plug 6 and the discharge time T is stored in a ROM 10 in advance. Based on the measurement of the discharge time T and the relationship, a computing part 12 computes the inter-electrode gapΔof the spark plug 6, with the computation result displayed on a determination display part 13.
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