A device for a valve actuator directed to measuring torque through linear displacement of a driving member is provided. The device comprises a valve actuator that includes an actuator motor and a driving member having a first end and a second end. A screw is coupled to the driving member and positioned between the first end and the second end. A gear configured to engage against the screw is positioned adjacent to the driving member. A spring element having a known constant is coupled to the second end of the driving member. The device further includes a linear potentiometer or a microswitch, and a method for measuring torque using the provided linear potentiometer or microswitch.

A strain-gauge-type torque detection part (20) of a strain wave gearing (1) comprises a first torque detection part (20A) and a second torque detection part (20B), which output detection signals of two independent systems. The first and second torque detection parts (20A, 20B) are provided with multiple sets of strain gauges (11) attached to a diaphragm (3c) of an externally toothed gear (3), at predetermined angular intervals around a central axis. A first detection signal (22A) from the first torque detection part (20A) and a second detection signal (22B) from the second torque detection part (20B) are combined after a gain adjustment and a combined signal (23C) is generated. Transmitted torque can be calculated on the basis of the first detection signal (23A), the second detection signal (23B), and the combined signal (23C). Three-system output, resulting from adding high-accuracy output (24C) to detection outputs (24A, 24B) of two independent systems, is obtained from a torque detection device (10).