US 5,348,396 AGranted

Method and apparatus for optical temperature measurement

AssigneeThe United States of America as represented by the United States Department of Energy

InventorsPatrick E. O'Rourke, Ronald R. Livingston, William S. Prather

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Abstract

A temperature probe and a method for using said probe for temperature measurements based on changes in light absorption by the probe. The probe comprises a first and a second optical fiber that carry light to and from the probe, and a temperature sensor material, the absorbance of which changes with temperature, through which the light is directed. Light is directed through the first optical fiber, passes through the temperature sensor material, and is transmitted by a second optical fiber from the material to a detector. Temperature-dependent and temperature-independent factors are derived from measurements of the transmitted light intensity. For each sensor material, the temperature T is a function of the ratio, R, of these factors. The temperature function f(R) is found by applying standard data analysis techniques to plots of T versus R at a series of known temperatures. For a sensor having a known temperature function f(R) and known characteristic and temperature-dependent factors, the temperature can be computed from a measurement of R. Suitable sensor materials include neodymium-doped boresilicate glass, accurate to .+-.0.5.degree. C. over an operating temperature range of about -196.degree. C. to 400.degree. C.; and a mixture of D.sub.2 O and H.sub.2 O, accurate to .+-.0.1.degree. C. over an operating range of about 5.degree. C. to 90.degree. C.

Claims20

Dependent claims

A method for measuring temperature, said method for use with a source of light, a detector, and a temperature sensor having at least one isobestic wavelength, said sensor absorbing light in a temperature-dependent manner within a characteristic wavelength range, said method comprising the steps of:

transmitting light from said light source through said temperature sensor to said detector;
measuring the intensity I.sub.b of light transmitted through said sensor at a first wavelength, said first wavelength being outside said characteristic wavelength range;
measuring the intensity I.sub.I of light transmitted through said sensor at said isobestic wavelength;
measuring the intensity I.sub.A of light transmitted through said sensor at an analytic wavelength, said analytic wavelength being within said characteristic wavelength range;
computing the quantities A.sub.I =-ln (I.sub.I /I.sub.b) and A.sub.A =-ln (I.sub.A /I.sub.b);
computing the ratio R.sub.AI =A.sub.A /A.sub.I ;
and
computing said temperature, whereby said temperature may be determined from a function of said ratio, said function formed by
(a) while maintaining said sensor at a known temperature, measuring said intensity I.sub.b, measuring said intensity I.sub.I, and measuring said intensity I.sub.A,
(b) computing said quantities A.sub.I and A.sub.A from said measurement at said known temperature.
(c) computing said ratio R.sub.AI,
(d) repeating steps (a) through (c) with said sensor maintained at different known temperatures to produce a plurality of temperature measurements and a plurality of ratio measurements, and
(e) obtaining said function by correlating said pluralities of temperature and ratio measurements.

10 more elements

A temperature probe for use with a source of light and a detector, said probe comprising:

a temperature sensor having
a substantially optically-transparent housing, and
a mixture of D.sub.2 O and H.sub.2 O contained within said housing,
said sensor transmitting at least a portion of the light incident thereon in relation to the temperature of said sensor, said transmitted light having a characteristic factor and a temperature-dependent factor, the ratio of said temperature-dependent factor to said characteristic factor being a known function of temperature;
first means for transmitting light from said source to said temperature sensor;
and
second means for transmitting light from said temperature sensor to said detector.

4 more elements

A method for measuring temperature in a region, said method comprising the steps of:

transmitting light through a temperature sensor located in said region, said sensor absorbing a portion of said light in relation to the temperature of said sensor;
measuring the intensity of said light transmitted through said temperature sensor, said transmitted light having a characteristic factor and a temperature-dependent factor, the ratio of said temperature-dependent factor to said characteristic factor being a known function of temperature, said function found by
(a) measuring the intensity of light transmitted through said sensor at a known temperature,
(b) computing said characteristic factor and said temperature-dependent factor from said measurement,
(c) computing the ratio of said temperature-dependent factor to said characteristic factor,
(d) repeating steps (a) through (c) with said sensor maintained at different known temperatures to produce a plurality of temperature measurements and a plurality of ratio measurements, and
(e) obtaining said function by correlating said pluralities of temperature and ratio measurements;
computing said temperature-dependent factor;
computing said characteristic factor;
computing said ratio of said temperature-dependent factor to said characteristic factor;
and
computing said temperature using said ratio and said function.

9 more elements

Dependencies are inferred from the claim text.