Ultraminiature Angular Position Sensor Based on the Beta-Voltaic Principle

This paper introduces a new type of angular position sensor that features very high sensitivity and ultraminiature size, by comparison with other angular position sensors of the same dimensions. The sensor is based on the beta-voltaic principle. It consists of a radioactive β-particle source and a silicon p-n junction (acting as a detector). Both the source and the detector are semicircular in shape. If the source is positioned fully above the p-n junction, maximum dc voltage is obtained from the junction. As the angular position of the source is varied, the junction's output voltage drops in magnitude. The sensor measures 8 mm (diameter) × 0.7 mm (thickness). It can measure angular position as well as angular velocity. This new sensor will be ideal in applications such as digital cameras, smart tablets and cell phones, microrobotics, and so forth.