VEHICLE VELOCITY MEASURING SYSTEM EMPLOYING ADJUSTABLE WIDTH PULSE GENERATING SYSTEM

摘要

The speed of a vehicle is measured by an AC tachogenerator whose signals are converted to a train of double frequency pulses of constant amplitude and duration which are averaged to provide a measure of the speed. The pulse duration is adjustable to allow for variations in the diameter of the wheel associated with the tachogenerator. As shown Fig. 1, a vehicle 18 carries and AC tachogenerator 10 (12) on each of two axles 16, 14. The AC output triggers a multi-vibrator 48, 72 respectively at the zero levels, the pulse width being adjustable. The AC signals are also fed through frequency to analog converters 24, 26 and the larger output opens a gate 54 or 56 to enable the higher velocity to be measured. Thus the pulse train output from multivibrator 48 or 72, whichever represents the higher velocity, is fed through its opened gate 54 or 56, and the trailing edge of each pulse triggers a generator 90 of precision length pulses. The combined pulse trains are fed to a chopper 100 to produce pulses of constant amplitude and duration which are averaged to measure the speed.