Encoder, the mounting method of the encoder, the torque limiting mechanism, the driving device and a robot device

The encoder is fixed to the rotating shaft to rotate about a predetermined axis, a first rotating portion having a first pattern, is disposed in the non-rotating portion, a first detector for detecting a first pattern, around a predetermined axis rotating fixed to an output shaft for outputting at least a portion of the rotation of the rotary shaft, the second rotating portion having a second pattern, are arranged in non-rotary part, and a second detector for detecting a second pattern, and a reference unit for positioning the first detector and the second detector in the common position reference.