Vision Science : Photons to Phenomenology

Apparatus for measuring the ignition timing of a multi-cylinder internal combustion engine of the type having a pulse generator for indicating when the flywheel is in a predetermined position with respect to top dead center and in which an input signal is obtained from one particular spark plug and employed to initiate a counting operation employing a series of pulses which have a definite frequency relationship to the speed of the engine. The counting operation is started at the time that the pulse from the selected plug is received and is terminated when the reference signal is received from the pulse generator. Provision is made for compensating for different reference angles between the top dead center position and the position at which the pulse generator produces a pulse. This is done by presetting a counter in accordance with the reference angle.