Abstract: A two wire transducer and associated circuit processes an output voltage of the transducer to produce a first signal proportional to the position of a non-contacting movable core and to produce a second signal proportional to the temperature of operation of the transducer. The associated circuit includes an excitation source or current driver which provides a fixed frequency sinusoidal constant current across the transducer coil; and first and second demodulator circuits respectively extract position and temperature signals from the voltage developed across the coil of the transducer device. Thus, both temperature and position information are provided by a single device over a single pair of leads.

Abstract: A two-wire linear transducer comprised of a high permeability finite length core that is positioned with respect to a continuously wound variable pitch coil. The cores is displaced from the initial stroke position at one end of the coil to the opposite end thereof to produce an output signal which varies with displacement. The coil is energized by a constant alternating current source and has a winding configuration that produces an alternating output voltage. The imaginary component of the alternating output voltage varies linearly and continously in amplitude in proportion to the movement of the ferrite core from its initial stroke position to its end stroke position.

Abstract: The limited angle rotary force motor includes an inner pole member having multiple permanent magnets disposed on the exterior thereof and a longitudinal bore in which a rotor shaft is journaled for rotation. An annular low inertia coil assembly is positioned in spaced relation around the permanent magnets by sets of spoke-like arms extending from the rotor shaft through transverse openings in the inner pole means. An annular ferritic stainless steel outer pole sleeve is located in spaced relation around the coil assembly to complete the magnetic circuit and withstand hydraulic system pressure to which the motor components are exposed. The outer pole piece is part of the casing or housing for the servovalve.

Abstract: A small, light-weight direct drive servovalve includes a force motor with a stationary magnet structure and a moving coil with the moving coil coupled to a valve spool by means of a lever mechanism which is pivotally mounted on a pivot hub and which amplifies the actuating force exerted on the valve spool. The moving coil is suspended from the pivot hub by dual convoluted spring diaphragms and through the lever mechanism imparts a linear, reciprocating movement to the valve spool. A tandem valve spool and sleeve assembly is employed and provides for two separated hydraulic systems in a common housing. A fuel metering system for a gas turbine engine utilizing such a direct drive servovalve is provided.

Abstract: A pulse width modulator digital servo system combines a digital feedback signal, which is developed in response to a time based signal directly indicative of a positional physical parameter of a servo actuator, and a digital command signal, which is indicative of a desired position of the servo actuator, to produce a digital resultant signal. A pulse width modulator produces a control signal output that is pulse width modulated in accordance with the digital value of the resultant signal to control operation of the servo actuator to achieve the positional relationship commanded. The pulse width modulated control signal is balanced when the combined resultant signal has a predetermined or constant value and is unbalanced in respective directions depending on whether the combined resultant signal is larger or smaller than such predetermined value.