This library was created to work with the HC-SR04 Ultrasonic sensor. It features timing, metric conversion (centimeter and inch) and standard deviation methods. Some ideas were gleaned from a library created by ITead studio at iteadstudio.com. Look at the code and examples to understand how the library works. The standerd deviation code can be removed from the compilation resulting in a significant savings of resources. To do this comment the #define COMPILE_STD_DEV definition in the header file. mailto://carl.nobile@gmail.com