A new thin pickup coil for magnetic head type torque sensors

A new thin pickup head is proposed for magnetic-head-type torque sensors. The new pickup head consists of a stacked pair of figure eight coils, in which one of the coils is rotated in the coil plane by 90° from the other. The applied torque can be detected from the difference in self-inductances of a pair of the figure eight coils faced to the shaft through an air gap in a manner such that each figure eight coil sees the permeability of the shaft along either 45° or -45° from the axis. Unlike conventional pickup heads of 3-D structure, the proposed pickup head is thin, making it easy to build the torque sensor on a shaft. Experimental results using a magnetic yoke backing the pickup head show good linearity with small hysteresis