Duty Factor Analyser

by R. Behrens Applications of this duty factor meter include adjusting and setting up ignition systems, switch mode power supplies, PD modulators, and sensor signal converters. The circuit itself requires no adjustment, and has a duty factor resolution of 1%, or 1° in terms of the dwell angle. The duty factor range is 1% to 99% in the frequency range from 1.5 Hz to 10 kHz. The analyser is fed from 12 V and consumes only 50 mA, so that it can be readily used in a car. The measuring principle is 6 SUPPLEMENT 4 . ............. DUTY FACTOR ANALYSER straightforward. A PLL, ICs , is used to multiply the input signal by a factor 100 and to clock counter ICs-1C7, whose BCD outputs are applied to dis- play drivers IC2-ICS . The carry output of IC7 is fed back to the phase comparator in the PLL. The counter state is only latched and displayed upon the falling edge of the input signal. Since the counter always counts up to 100 (leading edge of the input signal); the output state that exists...