Patent ID: 7559260

Claim:
A rotational angle detecting device comprising: a detecting section for outputting a signal in accordance with a rotational angle of a rotary element; an angle detecting means for detecting a rotational angle of the rotary element based upon the signal outputted from the detecting section; an abnormality detecting means for detecting abnormality of an output system of the detecting section based upon the signal outputted from the detecting section; and a power supplying means for supplying power to the detecting section, wherein: a power supplying means performs supply and interruption of the power to the detecting section; and the abnormality detecting means compares a reference signal outputted from the detecting section when the power supplying means performs supply and interruption of the power in a case where no abnormality occurs in the output system of the detecting section with a signal outputted from detecting section when the power supplying means performs supply and interruption of the power, thereby detecting abnormality of the output system of the detecting section, wherein: the rotary element includes a steering shaft for a vehicle; and the power supplying means performs supply and interruption of the power to the detecting section by a predetermined time after a vehicular ignition switch turns on whereby the abnormality detecting means detects abnormality of the output system of the detecting section.