Generation of zero-level fluctuation and its reduction in the magnetic head type torque sensor with L-R bridge configuration

A theory is presented to describe the behavior of extrinsic zero-level fluctuations (ZLFs) for the magnetic-head-type torque sensor with L-R bridge configuration. A method for suppressing the extrinsic ZLF is derived from the theory. The method is demonstrated using an as-ground carbon steel (S45C in JIS) shaft of 12-mm diameter. It is found that the relationship between unbalances in the magnetic pickup and the generation of the external ZLF is well described by the theory. By combining the method for suppressing the extrinsic ZLF and surface processing of the shaft to reduce inhomogeneities, torque sensors for various control applications can be realized