US Patent 10160276 Contactless sensing of a fluid-immersed electric motor

A method and system for measuring rotor position or velocity in an electric motor disposed in hydraulic fluid. The system comprises a contactless position sensor that measures electric motor rotor via magnetic, optical, or other means through a diaphragm that is permeable to the sensing means but impervious to the hydraulic fluid. An electronic sensor is positioned outside the operating fluid, whereas the motor is located in the fluid volume.