A novel differential-type torque sensor based on capacitive edge-effect is designed for accurately and quickly detect torque. This torque sensor consists of a mechanical body and a printed circuit board（ PCB）. Two sensing dynamic electrodes on machine body are perpendicular to two corresponding sensing static electrode on PCB

and a differential structure is came into being. The capacitances between vertical plates are measured by a capacitance/digital converter

and the conversion relationships of"torque-capacitance "can be obtained. A commercial torque and rotational speed sensor is used as standard torque meter to conduct calibration and experimental verification of the designed torque sensor. The results show that the differential capacitive torque sensor has advantages of high sensitivity

repeatability and linearity

etc

and its sensitivity is about twice that of the non-differential type

and the non-linear error is smaller.