Abstract: A sensor system comprises a marginal oscillator. A tank circuit comprises inductive and capacitive elements including a probe arranged to generate an electromagnetic field in a sensing region. A non-linear drive circuit drives oscillation of the tank circuit by supplying a differential signal pair of complementary signals across the tank circuit, sustaining the oscillation on the basis of at least one of the complementary signals. A detection circuit detects a characteristic of the oscillation of the tank circuit that is dependent on the electromagnetic properties of the contents of the sensing region and to derive a signal representing the at least one characteristic. The differential signaling provides numerous advantages, including improved accuracy and signal-to-noise.

Abstract: Fluid sensor and method comprising: an oscillator having operating characteristics. Permittivity sensing element coupled to the oscillator and arranged to alter the operating characteristics of the oscillator in response to changes in permittivity presented to the permittivity sensing element. Reference element comprising an electrical impedance having a real and imaginary component controllably coupled to both the oscillator and the permittivity sensing element and arranged to alter the operating characteristics of the oscillator. Method of measuring the composition of a fuel comprising the steps of: measuring a real permittivity of the fuel. Measuring an imaginary permittivity of the fuel. Determining a proportion of biodiesel in the fuel based on the measured real permittivity. Determining a proportion of unrefined oil in the fuel based on the measured imaginary permittivity.

Abstract: A sensor arrangement for a rotatable element comprises two coils capable of being driven by oscillatory drive signals to generate electromagnetic fields. The coils are in different positions overlying a cylindrical portion of the rotatable element that has a target feature configured to interact with the generated electromagnetic fields when the target feature is aligned with the coils. Alignment between the target feature and the coils occurs at angular positions of the rotatable element that are offset for respective coils. Thus, by detecting a characteristic of the signals developed across the coils allowing derivation of an angular velocity signal representative of angular velocity. Also, the degree of interaction between the target feature and the electromagnetic fields varies with the axial position of the rotatable element, differentially between the coils, allowing derivation of an axial position signal representative of the axial position of the rotatable element.

Abstract: A cavity resonator system for measuring EM properties of the contents of a pipe portion comprises a primary resonator and a secondary resonator each with the same configuration comprising a conductive casing that defines a cavity and has openings for receiving a pipe portion, insulator material disposed inside the cavity, and antennae for generating and detecting a resonant EM field inside the cavity. In addition, the secondary resonator comprises at least one conductive screening ring that extends around the location occupied by a pipe portion for screening the interior of the ring from the field generated inside the cavity of the secondary resonator. By combining measures of parameters of the field from both resonators, the system may be used to generate a measure representative of EM properties of the contents of the pipe portion that is compensated for variation in the EM properties of the insulator material.

Abstract: A sensor system comprises a marginal oscillator. A tank circuit comprises inductive and capacitive elements including a probe arranged to generate an electromagnetic field in a sensing region. A non-linear drive circuit drives oscillation of the tank circuit by supplying a differential signal pair of complementary signals across the tank circuit, sustaining the oscillation on the basis of at least one of the complementary signals. A detection circuit detects a characteristic of the oscillation of the tank circuit that is dependent on the electromagnetic properties of the contents of the sensing region and to derive a signal representing the at least one characteristic. The differential signaling provides numerous advantages, including improved accuracy and signal-to-noise.

Abstract: A cavity resonator system for measuring EM properties of the contents of a pipe portion comprises a primary resonator and a secondary resonator each with the same configuration comprising a conductive casing that defines a cavity and has openings for receiving a pipe portion, insulator material disposed inside the cavity, and antennae for generating and detecting a resonant EM field inside the cavity. In addition, the secondary resonator comprises at least one conductive screening ring that extends around the location occupied by a pipe portion for screening the interior of the ring from the field generated inside the cavity of the secondary resonator. By combining measures of parameters of the field from both resonators, the system may be used to generate a measure representative of EM properties of the contents of the pipe portion that is compensated for variation in the EM properties of the insulator material.

Abstract: A sensor arrangement for a rotatable element comprises two coils capable of being driven by oscillatory drive signals to generate electromagnetic fields. The coils are in different positions overlying a cylindrical portion of the rotatable element that has a target feature configured to interact with the generated electromagnetic fields when the target feature is aligned with the coils. Alignment between the target feature and the coils occurs at angular positions of the rotatable element that are offset for respective coils. Thus, by detecting a characteristic of the signals developed across the coils allowing derivation of an angular velocity signal representative of angular velocity. Also, the degree of interaction between the target feature and the electromagnetic fields varies with the axial position of the rotatable element, differentially between the coils, allowing derivation of an axial position signal representative of the axial position of the rotatable element.

Abstract: Target sensor comprising: sensor probe having a resonance frequency that changes as the separation of the sensor probe and a target changes. Oscillator arranged to apply a radio frequency (RF) signal to the sensor probe, the oscillator having: control circuitry configured to regulate the frequency of the RF signal applied to the sensor probe to below the resonance frequency of the sensor probe. Detector arranged to detect an electrical characteristic of the oscillator that varies with the impedance of the sensor probe indicating an interaction of the sensor probe with the target.

Abstract: An electromagnetic field sensor assembly for blade tip clearance measurement in a gas turbine engine is disclosed that includes a ceramic sensor body, a multi-layered wire coil wound about a distal end portion of the sensor body for producing an electromagnetic field, a ceramic well enclosing the sensor body and the coil, and a metallic housing surrounding the well and having an open distal end.

Abstract: A target or rotor blade clearance measurement device is disclosed for indicating an interaction of a measurement probe with a target or rotor blade. In a preferred embodiment, the measurement device comprises a measurement probe containing a coil, a frequency source arranged to apply an input alternating signal to the measurement probe, and a frequency regulator arranged to regulate the input alternating signal at a frequency below the resonance frequency of the measurement probe. A detector is arranged to detect an output signal from the measurement probe at a frequency of the frequency source which varies in amplitude with an admittance and resonance frequency of the measurement probe. A circuit is arranged to scale the amplitude of the output signal detected by the detector according to the amplitude of the input signal provided by the frequency source.

Abstract: An electromagnetic field sensor assembly for blade tip clearance measurement in a gas turbine engine is disclosed that includes a ceramic sensor body, a multi-layered wire coil wound about a distal end portion of the sensor body for producing an electromagnetic field, a ceramic well enclosing the sensor body and the coil, and a metallic housing surrounding the well and having an open distal end.

Abstract: Permittivity sensor and method comprising: an oscillator (L,40) having operating characteristics (F,V); permittivity sensing element (30) coupled to the oscillator and arranged to alter the operating characteristics of the oscillator in response to changes in permittivity presented to the permittivity sensing element; a reference element (110) switchably (220) coupled to both the oscillator and the permittivity sensing element and arranged to alter the operating characteristics of the oscillator. Method of measuring the composition of a fuel comprising the steps of: measuring a real permittivity of the fuel; measuring an imaginary permittivity of the fuel; determining a proportion of biodiesel in the fuel based on the measured real permittivity. Determining a proportion of unrefined oil in the fuel based on the measured imaginary permittivity.

Abstract: An electromagnetic field sensor assembly for blade tip clearance measurement in a gas turbine engine is disclosed that includes a ceramic sensor body, a multi-layered wire coil wound about a distal end portion of the sensor body for producing an electromagnetic field, a ceramic well enclosing the sensor body and the coil, and a metallic housing surrounding the well and having an open distal end.

Abstract: An electromagnetic field sensor assembly for blade tip clearance measurement in a gas turbine engine is disclosed that includes a ceramic sensor body, a multi-layered wire coil wound about a distal end portion of the sensor body for producing an electromagnetic field, a ceramic well enclosing the sensor body and the coil, and a metallic housing surrounding the well and having an open distal end.

Abstract: Position sensor (10?) and method for measuring the position of an object comprising, a sensing element and an oscillator (30) coupled to the sensing element such that an electromagnetic field is emitted from the sensing element. An output, arranged to provide a signal, varies in dependence upon a change in an electrical property of the oscillator (30). Change in object position relative to the sensing element alters the electrical property of the oscillator (30). Sensing element comprises at least one discontinuity arranged to perturb the signal at a predetermined object position. Alternatively, there is a temperature compensator in proximity to the sensing element and arranged to compensate the signal for changes in temperature.