BAT is an Ultrasonic Sensor Distance Measuring module (RoHS). It can detect objects within an area and measure the distance between BAT and objects. Ultrasonic sensors send a 40KHz high frequency sound and detect the signal reflected back from nearby objects. BAT then output a plus which can express the range. Features Ranging distance: 2cm - 500 cm Power supply: 5VDC. Effectual angle: 15 degree Resolution: 0.2cm There are 4 pins out of the module: VCC Trig Echo and GND. So it's a very easy interface for controller to use it for ranging. The all process is : pull the Trig pin to high level for more than 10us impulse the module start ranging ; finish ranging If you find an object in front Echo pin will be high level and based on the different distance it will take the different duration of high level. So we can calculate the distance easily: Distance = ((Duration of high level) (Sonic: 340m/s))/2