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AssigneeRosemount Inc.
InventorJames S. Johnston
Estimating the term…
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.
Displacement sensing apparatus, comprising a light conducting member incorporating a fluorescent substance;
Apparatus for measuring a parameter, comprising an elongate light conducting member incorporating a fluorescent substance, an interface at which light conducted along the member can be received from the member, a radiation source capable of irradiating up to a predetermined maximum length of the member to cause fluorescence of said substance contained in said length, light generated by said fluorescence being conducted along said member to the interface, occluding means located between the source and the member to cause a partial length only of the member to be irradiated by the source, said partial length corresponding to the parameter to be measured, and receiving means responsive to the intensity of light generated by the fluorescence and received from the member at the interface to provide an indication of the length of the member being irradiated and hence of the parameter to be measured, wherein the light conducting member is arranged so as, when irradiated, to fluoresce at two different light wavelengths at which there are substantially different attenuation coefficients for light conducted along the member, said receiving means being responsive to the respective intensities of light at the two wavelengths received from the member at the interface to provide said indication in a form which is independent of the intensity of the radiation source.
Apparatus for measuring the attenuation of light transmitted between two points, comprising a first length of light conducting member incorporating a fluorescent substance at least at one location along said first length, a second length of light conducting material incorporating a fluorescent substance at least at one location along said second length, means establishing a two directional light path between the said locations in said first and second lengths, respective sources of radiation to irradiate said locations in said first and second lengths causing fluorescence of said substance, light generated by said fluorescence being conducted from each said location, both along said light path towards and beyond the other said location, and in the reverse direction along the respective length of light conducting member away from the other said location, a respective receiving means for each said length of light conducting member and responsive to the intensities of light conducted along the respective said lengths both directly from said location in the respective said length and from said location in the other said length, means modulating the light generated by said fluorescence at each of said locations so that the intensities from the two locations can be separately detected at each said receiving means, and attenuation measuring means responsive to the detected intensities of light from each of said locations as received at each of said receiving means to provide an indication of variations in the attenuation of the light along said light path between said two locations.
Dependencies are inferred from the claim text.