Patent ID: 8671773

Claim:
An electronic flow meter comprising: magnetic sensors that magnetically detect a rotational frequency of a rotator rotating according to a flow rate of a fluid and output first and second signals, respectively according to the rotational frequency of the rotator as detected; drivers that drive the magnetic sensors, respectively; a first comparator that samples the first signal outputted by the magnetic sensor on the basis of a sampling signal; a second comparator that samples the second signal outputted by the other magnetic sensor on the basis of the sampling signal; a two-phase encoder that determines whether the rotator is rotating in a normal direction or a reverse direction on the basis of the first and second signals sampled by the first and second comparators, respectively and causes a counter to count up or to count down according to the normal or the reverse direction as determined, thereby outputs an event count signal; and a rotational speed timer that works out the rotational frequency of the rotator from the event count signal outputted by the two-phase encoder, and sets frequencies of the respective sampling signals of the first and second comparators at a time when the rotational frequency of the rotator is measured next time, and respective drive periods of the drivers in accordance with the rotational frequency of the rotator as calculated.