Method and device for contactless position measurement

If outputs of a couple of Hall ICs (31, 32) constituting a throttle valve position sensor (30) are within an operating range of throttle valve position, and if a relationship between the outputs are within a predetermined error range, both the Hall ICs (31, 32) are determined to be normal. In contrast, if the outputs are equal to an upper clamp voltage or a lower clamp voltage, and if a relationship between the outputs is out of the predetermined error range, at least one of the Hall ICs is determined to be abnormal. Furthermore, if the outputs are within a failure reference voltage range, it is determined that there is an abnormality between the throttle valve position sensor and an ECU. In this way, abnormalities in the sensor (30) and abnormalities between the sensor (30) and the ECU can also be detected.