US Patent 8957674 Pump with rotor position measurement system

A pump comprising an electrical motor drive (2) and a pump engine (3), the pump engine having a stator portion (32) and an axially and rotatably movable rotor portion (30) mounted in the stator portion. The electrical motor drive comprises a rotor (6) with a permanent magnet (20), a stator (4) with a magnetic circuit (10) and one or more coils, and a position sensor (8) comprising at least one magnetic field detector (24a, 24b) positioned in the proximity of the rotor permanent magnet and configured to detect both rotational and axial movement of the rotor.