IGNITION TIMING MEASURING APPARATUS

摘要

Apparatus for measuring the ignition timing of an internal combustion engine of the type having a pulse generator for indicating when the flywheel is in a predetermined position subsequent to top dead center and in which a pulse of predetermined amplitude is initiated by a signal from one spark plug and is terminated by a signal derived from the pulse generator. Correction is made for the reference angle between the top dead center position of the piston and the occurrence of the signal from the pulse generator by algebraically adding to the pulses a DC correction which is adjusted to conform with the knows: reference angle. The adjusted pulses are applied to a meter to indicate the amount of ignition advance or retard. A second meter indicates the amount of the correction voltage. The apparatus also has novel calibrating means for applying to the timing device two spaced voltage pulses spaced apart by the distance of a half cycle of a periodically varying commercial voltage of known frequency. A second periodically varying voltage is derived from the first periodically varying voltage by a frequency divider so that there is a definite frequency relationship between the two voltages. The width of a half cycle of the first voltage pulse thus has a predetermined angular relationship to the half cycle of the second voltage. The apparatus is calibrated by adjusting the apparatus so that the angular relationship displayed on the reference angle meter corresponds to the angular relationship between the two frequencies.