Fiber optic refractometer
OwnerCharles F. Cole, Jr.inventor
Life of this patent
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Abstract
A fiber optic refractometer is disclosed for use in on-line measurement of the refractive index of a process fluid. The refractometer does not require light to pass through the process fluid and is hence unaffected by the presence of light diffusing particulate matter in the process fluid. A particular application for which the refractometer is well-suited is the on-line measurement of the hydrogenation state of edible oils (which correlates with refractive index) during the partial hydrogenation process.
Claims18
A method for measuring the refractive index of a fluid, comprising the steps of:
- a) radiating light at a known wavelength .lambda..sub.R into an optical waveguide having a refractive index n.sub.co and measuring the optical power transmitted therethrough, wherein the value of n.sub.co is known at wavelength .lambda..sub.R as a function of temperature, and further wherein at least part of the wave guide is in contact with a fluid whose refractive index is to be measured;
- b) varying the temperature of the fluid and fluid contacted waveguide section until the transmitted optical power through the waveguide reaches a minimum, at which point the refractive indices of the waveguide and fluid are deemed to be equal;
- c) measuring the temperature T.sub.min at which the transmitted optical power minimum occurs;
- and,
- d) determining the refractive index of the fluid at wavelength .lambda..sub.R and temperature T.sub.min from the known value of n.sub.co at T.sub.min.
A refractometer for measuring the refractive index of a fluid, comprising:
- an optical waveguide with a refractive index whose value is known as a function of temperature;
- a cell for containing a sample of a fluid with a section of the waveguide in contact with the fluid within the cell;
- means for radiating light into the waveguide and means for sensing the optical power transmitted therethrough;
- means for sensing and regulating the temperature of the fluid within the cell;
- and
- means for automatically varying the temperature of the fluid within the cell in accordance with the sensed optical power until the optical power transmitted through the waveguide reaches a minimum at a temperature T.sub.min at which point the refractive index of the fluid and the refractive index of the waveguide are deemed to be equal.
An apparatus for measuring the hydrogenation state of an oil where the value of the oil's refractive index as a function of its hydrogenation state and temperature is known, comprising:
- an optical waveguide with a refractive index whose value at wavelength .lambda..sub.R is known as a function of temperature;
- a cell for containing a sample of an oil with a section of the waveguide in contact with the oil within the cell;
- means for radiating light of wavelength .lambda..sub.R into the waveguide and means for sensing the optical power transmitted therethrough;
- means for sensing and regulating the temperature of the oil within the cell;
- means for automatically varying the temperature of the oil within the cell in accordance with the sensed optical power until the optical power transmitted through the fiber reaches a minimum at a temperature T.sub.min at which point the refractive index of the oil and the refractive index of the waveguide are deemed to be equal;
- means for calculating the refractive index of the oil at temperature T.sub.2 from the known waveguide refractive index at T.sub.min whose value is known as a function of temperature;
- and
- means for calculating the hydrogenation state of the oil from the calculated refractive index of the oil at T.sub.2 and the known dependence of the oil's refractive index on hydrogenation state and temperature.
Dependencies are inferred from the claim text.