Obtaining data from a ammeter using image-based movement tracking

Power data is obtained from a power meter that utilizes a rotatable element (e.g., a disk) by illuminating a spot on the rotatable element, capturing image information from the surface of the rotatable element, processing the image information to track movement of the rotatable element, and converting the movement information to digital power data. Movement of the rotatable element is tracked by capturing successive frames of image information and correlating common features in the image frames to determine the magnitude of movement of the common features.