The Distance Sensor uses two ultrasonic sensors to detect the distance between current position and object. In most situation, the availability of ultrasonic allow it provided quick and accurate result.
 
Working Principle
The Distance sensor use the ultrasonic to measure the distance between the sensor and object. When the sensor emit a wave of ultrasonic wave, it will start passing thought the air until it hit the object, then rebound and back to the receiver. The sound wave travel in the air is approximately 340meter per second, with it, use the interval time between sent and received can calculate the distance.