Patent ID: 6054927
Filing Date: 2000-04-25
Classification: G01S,G01V

Abstract:
A sensor module comprising:a sensor operative to sense a condition of a monitored zone and provide a sensor signal having an electrical characteristic which varies as a function of the sensed condition;a first circuit operative to perform a first transfer function operation on the sensor signal and provide a first signal having a characteristic that varies as a function of the sensor signal;a second circuit operative to perform a second transfer function operation on the sensor signal and provide a second signal having a characteristic that varies as a function of the sensor signal;a comparator operative to compare the first and second signals and provide a comparator output signal having a characteristic that varies between at least two conditions as a function of the first and second signals; anda third circuit operative to determine an indication of the number of transitions between the at least two conditions of the comparator output signal, said third circuit operative to determine a change in the condition of monitored zone indicative of the presence or absence of an object within the monitored zone based on the indication of the number of transitions between the at least two conditions of the comparator output signal.