Plural wavelength fiber optic liquid level sensor for multiple liquids
First Claim
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1. A system for measuring the thickness of layers of immiscible layers of different liquids in a container, comprising:
- a light source for generating light at respective wavelength bands at which the respective liquids are highly absorptive;
an optical fiber having one end into which the light from said light source is injected, and a sensing length of fiber extending into said container and through said layers of liquids, said sensing length of fiber characterized in that it comprises a core clad by a cladding layer of a material and thickness selected to provide significant evanescent wave loss of said absorptive wavelength band light when immersed in said respective liquid which is highly absorptive at said wavelength band and;
means for determining the light loss from the sensing fiber due to evanescent wave loss and processing said light loss to determine the thickness level of each respective liquid in said container.
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Abstract
A fiber optic liquid level sensor for measuring the level of multiple immiscible liquids in a container (20). An end of an optical fiber (24) is immersed in the liquids in the container (20). Light is injected into the other end of the fiber. The ratio of transmitted to the reflected light is dependent on the evanescent mode losses to the liquids in the container. The levels of the liquids are derived from the losses, since the absorption per unit length of the fiber is different for each liquid. The relative amounts of liquids in the container are obtained from the amount of absorption.
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Citations
10 Claims
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1. A system for measuring the thickness of layers of immiscible layers of different liquids in a container, comprising:
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a light source for generating light at respective wavelength bands at which the respective liquids are highly absorptive; an optical fiber having one end into which the light from said light source is injected, and a sensing length of fiber extending into said container and through said layers of liquids, said sensing length of fiber characterized in that it comprises a core clad by a cladding layer of a material and thickness selected to provide significant evanescent wave loss of said absorptive wavelength band light when immersed in said respective liquid which is highly absorptive at said wavelength band and; means for determining the light loss from the sensing fiber due to evanescent wave loss and processing said light loss to determine the thickness level of each respective liquid in said container. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for measuring the thickness of immiscible layers of different liquids in a container, characterized by a sequence of the following steps:
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disposing a sensing length of an optical fiber into the liquid container so that it extends through said layers of liquids, said sensing length of fiber characterized in that it comprises a core clad by a cladding layer of a material and thickness selected to provide significant evanescent wave loss when immersed in a particular one of said liquids at a wavelength band at which the respective liquid is highly absorptive; injecting light at said respective absorptive wavelength bands into one end of said optical fiber; and determining the light loss from the sensing fiber due to evanescent wave loss and processing said light loss to determine the thickness level of each respective liquid in said container. - View Dependent Claims (10)
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Specification