Temperature measuring method and apparatus

Abstract

A method of measuring a temperature of an object body in an electric furnace, based on an intensity of a radiant energy emitted from the object body, the electric furnace being provided with an electric heater operable by application of a drive voltage thereto to heat the object body, the method comprising: a radiant-energy detecting step of detecting an intensity of a radiant energy emitted from the object body; a stray-light noise eliminating step of determining as a noise an intensity of a radiant energy of a stray light which is emitted from an inner wall surface of the electric furnace toward the object body and reflected by a surface of the object body, according to a predetermined relationship between the intensity of the radiant energy of the stray light and the drive voltage applied to the electric heater and based on an actually applied value of the drive voltage, and subtracting the intensity of the radiant energy of the stray light determined as the noise, from the detected intensity of the radiant energy emitted from the object body; and a temperature calculating step of calculating a temperature of the object body, based on the intensity of the radiant energy emitted from the object body from which the noise has been removed in the stray-light noise eliminating step. Also disclosed is an apparatus for practicing the method, which may include a shielding device disposed between the furnace walls and the object body.

Description

[0001] This application is based on Japanese Patent Applications Nos. 2001-312962 and 2001-312963 both filed on Oct. 10, 2001, the contents of which are incorporated hereinto by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a method and an apparatus which permit accurate measurement of temperature of an object body even in the case where the temperature of a wall such as a furnace wall surrounding the object body is different from that of the object body. [0004] 2. Discussion of Related Art [0005] Temperature measuring methods of non-contact type are industrially useful and widely employed. To practice such non-contact type temperature measuring methods, there are known a radiation thermometer operable to effect a monochromatic temperature measurement, and a radiation thermometer operable to effect a dichroic temperature measurement. The former thermometer measures the temperature of an object body by comparing a radi...

AI Technical Summary

Benefits of technology

[0010] The present invention has been developed in view of the findings discussed above. It is a first object of the present invention to provide a method which permits highly accurate measurement of a surface temperature of an object body in a furnace. A second object of the invention is to provide an apparatus suitable for practicing the method.

Problems solved by technology

Although this thermometer permits easy measurement of the temperature of the object body, it requires determination of the emissivity of the object body, and is not suitable for measuring temperature of an object body the emissivity of which changes.

The radiation thermometers of non-contact type capable of monochromatic or dichroic temperature measurement or other non-contact type radiation thermometers may suffer from insufficient accuracy of the temperature measurement of the object body, due to a stray light noise undesirably included in the light radiated from the object body.

Thus, the detected temperature of the object body is adversely influenced by the radiant energy of the stray light.

The degree of the adverse influence on the accuracy of measurement of the temperature of the object body increases with a rise in temperature of the inner wall surfaces of the furnace surrounding the object body, since the rise in the temperature of the surroundings causes an increase in the intensity of the radiant energy emitted from the inner wall surfaces of the furnace, as the stray light noise

However, where the temperature in the furnace is relatively high, the water-cooled shielding plate cools down the object body, leading to deterioration of the temperature measurement accuracy.

This apparatus suffers from a drawback that the measurement accuracy is not sufficiently high when the temperature distribution within the furnace wall is uneven, since the temperature of the furnace wall is detected by the radiation thermometer at only one local portion of the furnace wall.

Therefore, to employ a radiant energy emitted from one local portion of the entire wall surface as a radiant energy emitted from the furnace wall as a whole leads to deterioration in the accuracy of measuring the temperature of the object body.

Images