Abstract: A detector for detecting a characteristic and a speed of a vehicle includes a first magnetic field sensor. The first magnetic field sensor includes a magnetically variable resistor that changes resistance in response to being exposed to a magnetic field. A bias is applied to the magnetically variable resistor and a change in the resistance thereof in response to an applied magnetic field is detected by an amplifier. The amplifier generates a first analog signal indicative of changes in the resistance of the magnetically variable resistor. A differentiating circuit differentiates the first analog signal and produces a first output that changes binary state in response to detecting a predetermined change in the differentiated first analog signal. A counter accumulates values at a predetermined rate and a microprocessor stores values of the counter corresponding to each change in the binary state of the first output of the differentiating circuit.

Abstract: A detector for detecting a characteristic and a speed of a vehicle includes a first magnetic field sensor for generating a first analog signal indicative of changes in magnetic field strength adjacent the first sensor in response to the vehicle passing. A differentiating circuit differentiates the first analog signal and produces a first output that changes binary state in response to detecting a predetermined change in the differentiated first analog signal. A counter accumulates values at a predetermined rate and a microprocessor stores values of the counter corresponding to each change in the binary state of the first output of the differentiating circuit. The microprocessor converts the stored counter values into a first time series profile corresponding to changes in the first output of the differentiating circuit and accumulates and stores a count of a characteristic of the passing vehicle based on the first time series profile.