A Figure-of-Eight Flexible Pickup Coil for a Magnetostrictive Torque Sensor

A new structure of the pickup coil made on a double-layered flexible printed circuit board (PCB) is proposed for a magnetostrictive torque sensor. The pickup coil employs a pair of figure-of-eight coils in which one coil is 90deg angle rotated from the other. Each of figure-of-eight coils has 14 turn windings made of 18-mum-thick copper conductor with 100-mum/100-mum line and space. The shape of the coil is a square, and its side length is 15 mm. A torque sensor is constructed by using a shaft with a magnetostrictive sleeve made of a martensitic stainless steel. The pickup coil system was coupled to it with an airgap of 0.3 mm. The performance of the torque sensor is reported