The Grove - Ultrasonic Distance Sensor is an ultrasonic transducer that utilizes ultrasonic waves to measures distance. It can measure from 3cm to 350cm with the accuracy up to 2mm.  It is a perfect ultrasonic module for distance measurement, proximity sensors, and ultrasonic detectors. 

 

This module has an ultrasonic transmitter and an ultrasonic receiver so you can consider it as an ultrasonic transceiver. Familiar with sonar, when the 40KHz ultrasonic wave generated by the transmitter encounters the object, the sound wave will be emitted back, and the receiver can receive the reflected ultrasonic wave. It is only necessary to calculate the time from the transmission to the reception, and then multiply the speed of the sound in the air(340 m/s) to calculate the distance from the sensor to the object. 

Here is a simple example of how an ultrasonic sensor works to measure distance:

• Firstly, the transmitter (trig pin) sends a sound wave
• The object picks the wave up, reflecting it back to the sensor.
• The receiver (echo pin) picks it up

 

Compared with traditional ultrasonic modules HC-SR04, the Grove - Ultrasonic Distance Sensor integrates a single-chip microcomputer, and the transmitting signal and the receiving signal share one pin by time-division multiplexing, so only one I/O pin is occupied. Another difference is that HC-SR04 only supports 5v voltage, while Grove - Ultrasonic Distance Sensor supports 5v and 3.3v. As we know, the Raspberry pi I/O only supports 3.3v. Therefore, Grove - Ultrasonic Distance Sensor can be directly connected to the I/O of the Raspberry Pi, but HC-SR04 needs to use a voltage conversion circuit.