Non-contact torque measurement on a rotating shaft incorporating a mechanical resonator

A contactless method of torque measurement on a rotating shaft has been developed. A triple-beam metallic resonating tuning fork mounted on a stiff torsion bar in-line with the shaft is used. An inductive drive and capacitive pick-up link with a simple phase lock loop provide the frequency output at about 4.5 kHz. Tests have been performed for static torque up to 13 Nm with sensitivity 60 Hz/Nm and for rotational torque up to 4.5 Nm with sensitivity 55 Hz/Nm (rotational speeds up to 150 rev/min). The design methodology, construction and initial results are discussed, and further developments are outlined.