Circuit arrangement for producing a digital speed signal corresponding to the angular velocity of a wheel from the half cycle duration of the sinusoidal waveform generated by the wheel

A circuit for providing a digital wheel speed signal comprising:

• a. wheel sensor means for generating a sinusoidal waveform having a frequency directly proportional to the angular velocity of a vehicle wheel;
• b. a gating circuit connected with said wheel sensor means so as to be enabled during a first half cycle duration of said sinusoidal waveform;
• c. first pulse generator means for emitting pulses at a constant frequency;
• d. a first multi-stage digital counter to which said impulses are connected via said gating circuit only so long as said gating circuit is enabled, said first counter providing an output signal that varies inversely with the angular wheel velocity;
• and
• e. control means for modifying the output signal of said first counter so as to vary in direct proportion to the angular wheel velocity comprising:
• i. a second multi-stage digital counter;
• ii. first means for supplying impulses to said second counter at a frequency that changes exponentially;
• iii. a third multi-stage digital counter;
• iv. second means for supplying impulses to said third counter at a frequency that changes exponentially;
• v. comparator means for activating said second means only when the output signals of said first and second counters are equal;
• and
• vi. means for recognizing the final stage of said second counter to deactivate said second means, whereby the output of said third counter corresponds to the difference between the final stage output of said second counter and the output of said first counter following expiration of said first half cycle duration of said sinusoidal waveform.