Abstract: An alternator produces current that has an average component and a ripple component. The alternator testing apparatus produces one voltage representative of the magnitude of the peak-to-peak amplitude of the ripple component and a second voltage representative of the sum of the average component and the peak-to-peak amplitude of the ripple component. A series of comparators each have their signal inputs coupled to receive the first voltage and their control inputs coupled to a divider network which is in turn coupled to receive the second voltage. Indicators are coupled to the comparators.

Abstract: There is disclosed a transducer to sense the vacuum in the intake manifold of an engine or other chamber. The electrical signal it produces is converted into digital signals for operating a liquid crystal display. The output of the transducer is also coupled to a driver which is operable in one mode to produce energizing currents on all of its outputs corresponding to the amplitude of the electrical signal. The driver is coupled to LEDs which are thus illuminated. The driver is also operated in a second mode so that only one of the outputs is energized and in that mode the driver receives only the AC component of the transducer output.