Ultrasonic Sensor Module HC-SR04 provides 2cm ? 400cm non-contact measurement function, the ranging accuracy can reach to 3mm. The modules includes ultrasonic transmitters, receiver and control circuit.
Ultrasonic sensor module is a device which can measure the distance of an object by sending ultrasonic wave and then capturing the reflected wave and converting it into an electrical wave signal. The waves travel faster than the speed of audible sound wave.
It has two main components: the transmitter (which emits the sound using piezoelectric crystals) and the receiver (which encounters the sound after it has travelled to and from the target object).