This ultrasonic sensor module can be used for measuring distance, object sensors, motion sensors, etc. The high sensitive module can be used with a micro-controller to integrate with motion circuits to make robotic projects and other distance, position & motion-sensitive products. The module sends eight 40Khz square wave pulses and automatically detects whether it receives the returning signal. If there is a signal returning, a high-level pulse is sent on the echo pin. The length of this pulse is the time it took the signal from first triggering to the return echo. Ultrasonic Ranging Module HC-SR04 provides 2cm-400cm non-contact distance sensing capabilities, Ranging accuracy up to 3mm.