US Patent 10227860 Axial generator measurement tool

A measurement tool includes a rotor to rotate about a longitudinal axis, an axial gap generator having a stator assembly adjacent to the rotor, and a movable support structure to which the stator assembly is mounted. The axial gap generator generates a voltage signal as a function of a gap spacing between the stator assembly and the rotor, where the gap spacing is parallel to the longitudinal axis. The movable support structure moves the stator assembly parallel to the longitudinal axis based at least in part on a physical property of an environment about the movable support structure.