A reluctance-Hall Effect based linear digital angle sensor

A new angle sensor based on a combination of a reluctance technique and Hall-Effect principle is presented in this paper. The proposed sensor provides a linear, digital output proportional to the angle being sensed. The sensor consists of two identical ring shaped sheets, in parallel, and a permanent magnet, placed between the rings. This unit rotates in unison with the target. Two fixed Hall-Effect sensor ICs, which are 180° apart, are kept in the air gap between the rings. An analysis shows that the flux density seen by these fixed Hall-Effect ICs vary as a third order polynomial function of the angle being sensed. A new signal conditioning method that provides a linear digital output from the proposed sensor is presented. A prototype angle sensor and signal conditioning unit have been built and tested. Output of the prototype unit was linear across 0 - 110° and worst-case error was less than 1.2%. The proposed sensor is suitable for automotive and industrial applications, especially where center of the target is not easily accessible to employ the conventional magnetic sensors directly.