Flow sensor

摘要

A transmitter transmits an ultrasonic wave. A receiver receives the ultrasonic wave from the transmitter. An output signal of the receiver is amplified. A phase comparator outputs a voltage corresponding to the phase difference based on a high frequency signal generated by a high frequency signal oscillator and an output signal of a high frequency signal amplifier. A low frequency amplifier amplifies the output voltage of the phase comparator. A comparator compares the output signal of the low frequency amplifier with a reference voltage and outputs a pulse indicating the comparison result. A frequency divider divides the output pulse. A decoder decodes the output signal of the frequency divider for turning on light emission sections of a flow indicator in green in order.