Abstract: An apparatus is disclosed for measuring one or more parameters of a variable physical structure, at least one of the parameters being fluid level, position, velocity or acceleration. The apparatus includes an electromagnetic sensing element comprising at least two electrically conductive members that are electrically insulated from one another. A distributed capacitance and a distributed inductance are each formed along a length of the sensing element. The inductive reactance is at least ten percent of the capacitive reactance, thereby allowing the capacitance to be distributed, rather than acting as a “lump capacitance”. The distributed capacitance enables shaping of the electric and magnetic fields around the electromagnetic sensing element so that disturbance by nearby electromagnetic fields, conductors, and dielectrics is minimized. When the apparatus is configured as a fluid level sensor, the capacitance is affected by the permittivity and the level of the measured fluid.

Abstract: A method and apparatus are disclosed for monitoring a linear position, such as the distance between a sensing element and a movable object, and/or related parameters, such as displacement, direction, speed, velocity, and/or acceleration. The method utilizes a sensing element and an electrically conductive portion of the movable object, or a conductive target coupled to the movable object. The apparatus includes at least one sensing element formed by a section of a coupled slow-wave structure. The sensing element is connected to an RF or microwave generator, and an electronic circuit that converts at least one electromagnetic parameter of the section of the coupled slow-wave structure into a position reading. Electric and magnetic fields excited in the sensing element are split so that most of the electric energy is concentrated inside of the sensing element, while most of the magnetic energy is concentrated outside of the sensing element.

Abstract: Inductive position sensors and circuit configurations are disclosed for the measurement of linear, rotary, or curved position along a motion axis. The simplified sensor structures combine one or two parts of a movable core element with a simple planar substrate having first and second inductances connected in series. Movement of the core element in parallel to the planar substrate causing the impedance of at least one of the inductances to change. Simple circuit configurations are taught by which the impedance change is converted into a useful output signal that indicates position along the motion axis.

Abstract: A capacitive fluid level sensor is disclosed that operates without the use of a float, wherein sensing electrodes are spaced to form a measured capacitance that changes in accordance with a changing fluid level, the electrodes forming a sensing element, and being electrically insulated from the measured fluid. The sensing element is fabricated such that it can be attached to the outside of a dielectric wall of a vessel, or embedded within a dielectric material. An interdigital comb configuration of sensing element is also disclosed in which depressions or gaps are formed into a dielectric material that is present between the fingers of the comb.

Abstract: A magnetostrictive system is shown wherein there is included a wave guide but no return wire. The wave guide is folded and acts as the completed wire (whether solid or hollow) for conducting current for the current input pulse.