Abstract: In the use of a rotatable wheel and a rotation sensing device such as an incremental shaft encoder to measure the longitudinal translation of one member relative to another which extends longitudinally, for example, and wherein the wheel is supported for rotation on the longitudinally extending member by means of an inclined pivot arm supported on the one member, means are provided to automatically adjust the angular position of the stator portion of the shaft encoder to compensate for rotation of the wheel when the lateral spacing between the two relatively movable members changes, thereby eliminating a false indication of longitudinal translation.