An apparatus comprises a rotatable shaft and first and second targets coupled to the rotatable shaft so as to rotate therewith, a first probe for transmitting a first transmission signal to the first target and receiving a first response signal from the first target, and a second probe for transmitting a second transmission signal to the second target and receiving a second response signal from the second target. The apparatus further comprises a processor operatively coupled to the first and second probes for determining a torsional displacement of the shaft based on the first and second response signals received by the first and second probes, respectively. The processor then determines a torque imposed on the rotatable shaft based on its torsional displacement.