Rosemount Engineering Company Limited

Rosemount Inc.

Fisher-rosemount Ltd.

Rosemont Engineering Company Limited

James S Johnston

Melvyn S White

Ken Rendle

David W Pownall

Trevor Howard Neve

Christopher R Wright

Mark J Torres

Mike Lamdin

Dennis George Cope

Leslie Holland

A sensor (1) for sensing the displacement of a body (12) comprises a deformable strip (2) enclosed in a chamber 3. The strip is constrained under longitudinal and transverse constraint such that end portions (9, 10) of the strip are parallel to a direction of movement of the body, the strip being locally deformed in the form of an S-bend. A magnet operable between the strip and the body varies the location of the S-bend along the length of the strip according to the position of the body. Optical or electronic sensors are provided for indicating the sensed position. The sensor may be used for sensing liquid levels or displacement of moving bodies such as valve elements particularly in hazardous environments including aircraft.

Displacement sensor

In a method of analyzing a spectrally modulated light signal received from an interferometric transducer the value of an optical path difference associated with a parameter to be remotely sensed is encoded as a characteristic frequency of spectral modulation in the received light. The intensity of the received light is measured at a number of wavelengths within a selected range of wavelengths to obtain data defining a measured spectrum. Reference data is generated to represent a theoretical spectrum corresponding to a nominal optical path difference, the reference data being generated for a greater range of wavelengths than the selected range of wavelengths of the measured spectrum. The measured spectrum is correlated with successive portions of the reference data to identify a portion of the reference data exhibiting correlation with the measured spectrum, and an output signal is then generated which is representative of the location of the correlating portion within the wavelength range of the reference data. The method provides improved resolution for remote sensing of parameters such as pressure.

Method of decoding a spectrally modulated light signal

Displacement measurement apparatus (1) shown in FIG. 1 measures the position of a reading means (4) relative to a coded track (2) which carries a sequence of code elements (5). The track is encoded with a binary sequence such that reading a binary word at any position along the track uniquely identifies its position. The binary word is remotely sensed by a decoding means (18) via a fibre optic link (12). Position information is encoded optically by the reading means using an interferometer to frequency modulate the transmitted light and the decoding means has a second interferometer to analyse received light and produce an electrical output representing the binary word.

Displacement measurement apparatus with dual wedge interferometers

The invention relates to a deployable probe for measuring fluid pressures such as pitot and/or static pressure. The probe comprises an outer tubular casing, a probe member telescopically extendible from within the outer casing, spring means urging the probe member to extend longitudinally from an undeployed position which is wholly contained within the outer casing, a latch retaining the probe member in the undeployed position and releasable to deploy the probe, and extendible communicating means interconnecting the probe member and the outer tubular casing for supplying pressure indications from the probe member when the probe is deployed.

Deployable probe

Air data measurement apparatus for use on an aircraft, comprises a housing (1) open at both ends (2, 3) and divided into two chambers (8, 9) by a transverse wall (7). The leading end chamber (8) contains a total pressure sensor (11) and the trailing end chamber (9) contains a total temperature sensor assembly (15) whereby the apparatus functions to measure total temperature and pressure at a common point on an aircraft.

Air data measurement apparatus

An optical displacement sensor has an optically detectable coded track movable relative to a mask. The track is illuminated by light conducted by an optical fibre from a remote light source and the image of the track is focussed by a mirror on to the aperture of a second fibre. The mirror is mechanically movable to scan the image of the code over the fibre end to produce light pulses in the fiber which can be decoded at a remote receiver. The mirror is actuated electrically by electric energy from a photo-voltaic cell illuminated by light from a third fiber. Bits in the coded track are only partially opaque but the mask is fully opaque so the edges of the mask can be recognized by the receiver as the mirror is scanned.

Optical displacement transducer

A displacement sensor employs a light conducting member containing a fluorescent material. A source of irradiating light is movable relative to the light conducting member along a track. The irradiating light produces fluorescence within the member at a corresponding position. Light from the fluorescent point is conducted in both directions along the member and can thus be collected at one end for feeding to a photo detector. By monitoring variations in the intensity of light at the detector, the distance of the fluorescent point from the end of the member can be measured, and thus movement of the source along the track monitored. Additional embodiments enable dependency on the intensity of the irradiating light source and on losses between the light conducting member and the photo detector, to be mathematically eliminated. Further embodiments measure the attenuation between two fluorescent points in a length of fibre, and can be used to sense any physical parameter that can be arranged to affect this attenuation, such as stress, bending or temperature.

Light attenuation sensing apparatus for measuring physical parameters

Position measuring apparatus

A resistance thermometer element having a thin layer of platinum metal on an insulating substrate is formed by magnetron sputtering in a gaseous atmosphere containing at least 10% by volume of oxygen. Any balance gas has less than 10% by volume of argon, krypton and xenon. The atmosphere may have up to 100% oxygen with any balance gas being inert to platinum. Air can be used. A planar magnetron may be used.

Method of producing a resistance element for a resistance thermometer

A differential pressure sensor has a sensing diaphragm mounted in a body. The curvature of the diaphragm is representative of differential pressure across the diaphragm. Monochromatic light is direct from a source at the diaphragm to set up interference fringes which have varying spacings representative of the curvature, in the manner of Newton's rings. The fringes and their spacings are monitored and a computer calculates therefrom the curvature of the diaphragm and thence the pressure difference.

Differential pressure sensing apparatus

A differential pressure transducer of the diaphragm displacement type uses optical techniques to measure disphragm displacement. White light from a source is conducted by optical fibres to the transducer and interference is produced between light reflected at a thickened region of the diaphragm and a partially reflecting end face of the light conductor which is lapped flat and parallel to the diaphragm surface. The interfering reflected light is conducted back to a prism where it is dispersed onto photo-arrays. The wavelengths of dark fringes in the spectrum are measured to determine the displacement of the diaphragm. Measurements can be made on both sides of the diaphragm and used to eliminate dependence on reflective index.

Differential pressure measuring apparatus

A differential pressure transducer is a body with a pair of opposed sensing chambers bounded by diaphragms and associated surfaces of the body. The surfaces have conducting layers and form capacitors with the metal diaphragms. The chambers are connected together and fitted with a fixed mass of oil. A signal generating circuit produces electrical signals representing the values of the two sensing capacitors which are fed to a computer to calculate the differential pressure independent of temperature.

A solid state sensor element is a flat device having a film resistance thermometer on one face and a pair of spaced apart conductors on the other. The element is used for measuring selected properties of a material or the surrounding atmosphere and normally the spaced conductors are covered by a coating of a material which is electrically responsive to variations in a selected parameter of the ambient atmosphere.

Solid state sensor element

A catalytic gas detector is formed as a sandwich and comprises two flat printed film resistance thermometer sensors back-to-back with a layer of thermally insulating material between them. A coating of a suitable catalytic substance covers an exposed flat face of one of the two sensors.

Catalytic gas detector

An electric circuit includes three matched resistance thermometer sensors and is responsive to changes in rate of heat loss from at least one of them. The sensors are connected in a series-parallel arrangement to form one arm of a bridge circuit. An amplifier detects imbalance in the bridge and controls current flowing in the bridge to restore balance. Twice as much current flows in one sensor than in the other two, so that the one is maintained hotter. Environmental changes effecting a change in the rate of heat loss from the one sensor are detected as a change in current flowing in the bridge.

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Bognor Regis, United Kingdom

James S Johnston