Patent ID: 7564741

Claim:
A downhole measurement-while-drilling pulser actuator comprising a servo-valve movable between an open position which permits mud flow through a servo-orifice and a restricted position which restricts mud flow through the servo-orifice, the servo-valve powered to the open position and powered to the dosed position by a reversible electric motor, and further comprising a servo-controller for controlling the powering of the servo-valve by the electric motor wherein the servo-controller senses the position of a servo-poppet with respect to a servo-orifice, the servo-poppet and servo-orifice being components of the servo-valve, wherein the servo-controller senses the position of the servo-poppet by sensing whether movement of the servo-poppet is impeded, and wherein the servo-controller counts the number of rotations of the motor until the servo-poppet is impeded and compares the number of rotations to an expected number of rotations to determine the position of the servo-poppet with respect to the servo-orifice.