in a magnetic torsion meter for measuring the torque exerted on a rotating assembly , the rotating assembly includes first and second sections of a rotating shaft brought together by a torsion shaft . the torsion meter includes an exterior u - shaped fixed magnetic circuit . a continuous source of magnetic excitation creates a flux through the circuit and gaps of the first and second rotors . the first and second rotors each include an annular disk made of a non - magnetic material . the disks each include two concentric coils of ferromagnetic pins . the pins of the first rotor face the pins of the second rotor while defining two measuring gaps . the relative angular position of pins on both sides of the measuring gap is such that the reluctances are equal when no torque is applied but vary inversely when a nonzero torque is applied . the torsion meter includes at least two magnetic induction sensors housed in one of the smooth gaps of the u - shaped magnetic circuit . the sensors measure magnetic flux and output results to a treatment circuit , which produces a signal proportional to the angle of torsion .