Patent ID: 7591174

Claim:
A rudder angle sensor, which includes: a main drive gear interlocked with a steering shaft to reversibly rotate; a driven gear driven rotating by engaging with the main drive gear; a measuring mechanism measuring a rotation angle of the driven gear; and a calculation means calculating a rotation angle of the steering shaft based on a measured result of the measuring mechanism, said rudder angle sensor comprising: a storage means for storing a correction value to correct a rotational delay of the driven gear relative to the main drive gear caused by a backlash at a time of a reverse rotation, wherein the calculation means calculates the rotation angle of the steering shaft by correcting the measured result of the measuring mechanism based on the correction value stored in said storage means, the calculation means further comprising an interface for bringing in external data, wherein rotation angle data of the measurement shaft obtained from an encoder provided at the measurement shaft is brought into the calculation means from the interface, when the main drive gear is interlocked with the measurement shaft instead of the steering shaft, and wherein the calculation means calculates the correction value based on the rotation angle data brought in and the measured result of the measuring mechanism.