Abstract: A variable range gauge follower apparatus for measuring the diameter of work pieces comprising a pair of pivotable arms each having a contact at one end adapted to engage the surface of the work piece. Each of the arms has fixed to it for conjoint movement a segment member having an angular position Inductosyn at its circumferential edge. Associated with each Inductosyn is a magnet sensing head stationarily fixed so as to be able to sense the induced current as a function of the angular displacement of the segment. Means are provided for phase measurement of the two signals which when compared with a predetermined starting signal determines the angular change of the arms and thus the diameter of the work piece. The two arms are each mounted in a shaft journaled in a frame-like body and are coupled for conjoint rotation by a pair of meshing gears to establish an initial spacing or opening between the two arms. The gears are provided with means for their uncoupling during actual operation.