Torque sensor

Abstract

An excitation AC signal biased by a predetermined DC voltage is applied to a coil to allow a DC voltage component in a coil output signal to contain failure information about disconnection, partial disconnection, or the like of the coil. The DC voltage component contained in the coil output signal is detected, and the detected DC voltage is provided as an offset voltage for a failure diagnosis. Further, to check a peak level of the excitation AC voltage, a DC voltage corresponding to the peak level may be contained in the offset voltage. A differential amplifier circuit for obtaining a difference between a coil detection output AC voltage component and a reference AC voltage component outputs an obtained differential signal offset by the offset voltage. Accordingly, the differential signal containing the offset voltage as the failure information is transmitted to a circuit for torque measurement as a torque detection signal via a single output line. The circuit for torque measurement provides the torque detection data based on the transmitted differential signal and at the same time extracts the offset voltage to use it for the failure diagnosis.