GB1532786A - Apparatus for measuring the ignition timing of internal combustion engines - Google Patents

Abstract

1532786 Measuring ignition timing REGIE NATIONALE DES USINES RENAULT 8 Dec 1975 [10 Dec 1974] 50310/75 Heading GIU [Also in Division H3] In an ignition timing system of the type in which sparking plug pulses from a pick-up 111, Fig. 2 attached to the plug lead of a cylinder under examination, and top-dead centre pulses from a pick-up 101, alternately turn on and off a bistable trigger 21, to produce a pulse train whose markspace ratio, which is displayed on a meter 24, represents the timing of the sparking plug pulses with respect to top-dead centre, in order to compensate for variations in the level of background noise in the signal from the top-dead centre pick-up 101 resulting from variations in engine speed and irregularities in flywheels, the signal from the pickup is transmitted to the trigger via a coupling capacitor 108, a lead 13, a variable attenuator 15 in the form of a variable potential divider 105, T6, and a threshold circuit 16, 17, the variable attenuator being controlled by the average dc level of the signal from the pick-up, this being extracted by an amplifier 18 and a lowpass filter 19. Thus, in effect the signals from the pick-up 101 are so attenuated that their background noise is maintained constant, and then only those peaks that extend above the noise are transmitted to the trigger 21 by the threshold circuit 16, 17.