[Rickertsen2]

To clear things up, the HAL effect sensors have NOTHING TO DO WITH ACCELERATION, OR HEADING. They are a type of sensor that detects the presence of ferrous materias. They are designed to be mounted up against(but not touching) the teeth of a gear in a gearbox or other assembly. They will output 1 pulse for each gear tooth that goes by them. If for example you were to connect them to your drivetrain, you could count the number of pulses they output to figure out how far your robot had traveled. It is also possible to use them to determine the speed at which your robot (or some subassembly) is moving.