JPH06241906A - Radiation thermometric method and apparatus for matter in furnace - Google Patents

Abstract

PURPOSE:To obtain the temp. of a matter not affected by stray light noise by detecting the heat radiation from the matter on the basis of two wavelengths and connecting the characteristic function of a detection signal to black-body temp. with a correction factor changing corresponding to temp. and solving the expression equations of them. CONSTITUTION:The radiant light of matter itself to be measured and the reflected light from a furnace wall are incident on a radiation thermometer from the matter to be measured in a heating furnace and, when radiation is detected within respective wavelength regions lambda1, lambda2, respective sensor outputs m1, m2 are represented by formulae I, II [wherein epsilon1 and epsilon2 are emissivities in the wavelength regions lambda1, lambda2, Ts and Tw are the temp. of the matter and that of the furnace wall and f1 (Ts) and f2 (Tw) are sensor outputs within the wavelength regions lambda1, lambda2 where black bodies with temps. Ts, Tw are measured]. When C (T) is set to a correction factor changing corresponding to temp. and represented by C(T)=f1(T)/f2(T) and the formulae I, II are deformed, formulae III, IV, V are formed. Therefore, the temp. of the matter is calculated according to formula Ts=f<(-1)>(m). Herein, C (Ts) and C (Tw) are calculated by calculating approximate values of Ts and Tw at the time of C (T)=1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation temperature measuring method and radiation for an in-furnace object capable of highly accurately measuring the temperature of an object to be measured which has been heated in a furnace without being affected by stray light noise. Regarding temperature measuring device.

[0002]

2. Description of the Related Art A radiation thermometer is widely used as a temperature measuring means for measuring the temperature of a heating object processed in various heating furnaces from outside the furnace because it can measure the surface temperature of the object to be measured in a non-contact state. ing. However, in this radiant temperature measuring method, an unknown radiant light generated from the surrounding environment such as a furnace wall is reflected on the surface of the object to be measured, and a phenomenon occurs that disturbs the temperature measuring accuracy as a stray light noise component.

As a means for removing the effect of stray light noise which causes such a measurement error, a shield plate is used to remove an unknown stray light noise component and to correct a known stray light noise component generated from the shield plate. Radiation temperature measuring methods and devices as main components have been proposed (for example, JP-A-56-163428, JP-A-62-282231, JP-A2-138836, and JP-A-2-296121). etc). However, in the case of this method or apparatus, the condition inside the furnace is disturbed due to the installation of a foreign material such as a shielding plate, and it cannot be applied to a furnace such as a hot stove. In addition, when the contribution rate of stray light noise generated from the shield plate fluctuates, a new measurement error occurs.

In order to solve such a problem, JP-A-3-287025 discloses three types of spectral radiation of thermal radiation from an object to be measured, which have different wavelengths, polarizations, or measurement angles. Independently representing the relationship between the three equations that detect the luminance signal and represent these signals by the sum of the radiance signal component and the stray light noise component emitted by the measured object and the three emissivities corresponding to the radiance signal There is proposed a temperature measuring method and apparatus for obtaining the measured object temperature, the three spectral emissivities, and the ambient representative temperature by solving these two equations. According to this correction calculation method, it is possible to eliminate the influence of stray light noise without using a shield plate, but there is a problem that the device configuration, calculation means, etc. become complicated.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art by combining detection means for detecting the radiation of heat from an object to be measured as two different wavelengths and computing means corresponding to each detection signal. The purpose is to eliminate the influence of stray light noise components without using auxiliary means such as a shielding plate. To provide a device.

[0006]

In order to achieve the above-mentioned object, a radiation temperature measuring method for an in-furnace object according to the present invention detects thermal radiation from an object to be measured at two different wavelengths, and measures it against a black body temperature. The characteristic functions f ₁ (T) and f ₂ (T) of each detection signal are calculated by using a correction coefficient C (T) that changes with temperature, C (T).
We set f ₁ (T) = f ₂ (T), and using this relationship, we can express two detection signals by summing the signal component emitted by the measured object and the stray light noise component from the inside of the furnace. Solving with C (T) = 1, the assumed temperature Ts of the measured object and stray light noise component,
The correction coefficient C (T
s), C (Tw) are calculated, and the obtained calculated value is used to solve the expression of the detection signal to obtain the temperature of the measured object from which the influence of stray light noise is removed. To do.

Further, the radiation temperature measuring apparatus for in-furnace objects according to the present invention includes a radiation thermometer having a detection mechanism for separately detecting thermal radiation from an object to be measured at two different wavelengths, and each of the radiation thermometers. An arithmetic unit for obtaining the temperature of the object to be measured from the signal by the radiation thermometry method.

[0008]

The operation mechanism according to the present invention can be described as follows. As shown in FIG. 2, when the surface temperature of the measured object 2 inside the heating furnace 1 is to be measured by the radiation thermometer 3 installed outside the furnace, the surface of the measured object is indicated by two types of arrows. The radiant light of the measured object itself and the reflected light of the furnace wall both enter the radiation thermometer 3. When energy is detected in these two wavelength ranges λ ₁ and λ ₂ , the sensor outputs m ₁ and m ₂ in each wavelength range are approximately expressed by the following equations (1) and (2).
It is represented by.

M ₁ = ε ₁ · f ₁ (Ts) + (1−ε ₁ ) f ₁ (Tw) (1) m ₂ = ε ₂ · f ₂ (Ts) + (1−ε ₂ ) f ₂ (Tw) (2) In the equations (1) and (2), ε ₁ is the emissivity in the wavelength range λ ₁ , ε ₂ is the emissivity in the wavelength range λ ₂ , and Ts
Is the temperature of the object to be measured, Tw is the furnace wall temperature, f ₁ (Ts) is the sensor output in the wavelength range λ ₁ when measuring a black body at temperature Ts, and f ₁ (Tw) is a black body at temperature Tw Sensor output in the wavelength range λ ₁ at the time, f ₂ (Ts) is the sensor output in the wavelength range λ ₂ when measuring a black body at the temperature Ts, and f ₂ (Tw) is when the black body at the temperature Tw is measured Is the sensor output in the wavelength range λ ₂ .

In the above equations (1) and (2),
The term represents the emitted light from the measured object itself, and the second term represents the reflected light from the furnace wall. Here, the output characteristic function f at each wavelength is
The relationship of the following equation (3) is obtained between ₁ (T) and f ₂ (T). _{f 1 (T) = 1 /} C (T) · f 2 (T) = f (T) ... (3)

However, C (T) is a correction coefficient which changes with temperature and is a value showing the relationship of the following equation (4). C (T) = f ₁ (T) / f ₂ (T) (4)

Therefore, the equations (1) and (2) can be rewritten into the following equations (5) and (6) using the relation of the equation (4). m ₁ = ε ₁ · f (Ts) + (1−ε ₁ ) f (Tw) (5) m ₂ = ε ₂ · C (Ts) f (Ts) + (1−ε ₂ ) C (Tw) f (Tw)… (6)

Equation (5) is represented by (1-ε ₁ ) and equation (6) is represented by (1-
When divided by ε ₂ ) C (Tw), the following equations (7) and (8) are obtained.

When the equation (8) is subtracted from the equation (7) and summarized, the following equation (9) is obtained.

Therefore, ε ₁ , ε ₂ , C (Ts), C
If (Tw) is known, then from the measured values m ₁ and m ₂ , the above (9)
The right side of the equation can be obtained as the calculated value m. In this case, f (T) is a calibration curve obtained from the black body furnace test, and therefore the true temperature of the object to be measured is obtained by the following equation (10). Ts = f ^(-f) (m) (10)

However, since C (Ts) and C (Tw) are actually unknown, the temperature of the object to be measured cannot be calculated. In the present invention, the approximate C (Ts) and C (T
w) is calculated and the temperature of the object to be measured is calculated. In the relationship of the equation (9), assuming that C (T) = 1, m = m
^* A is calculated to determine the Ts ^* from equation (10). As Ts = Ts ^* , f (Tw ^* ) =
Calculate m ^** and obtain Tw ^{* in the same} manner as in equation (10). Cs (Ts) and C (T) where Ts = Ts ^* and Tw = Tw ^*
w) is calculated, and Ts is calculated from the relationship of equations (9) and (10).

In the above-mentioned arithmetic mechanism, the relation of the output characteristic function at each wavelength is related by using the correction coefficient C (T) determined by each function, so that the detection wavelength can be freely selected and the stray light noise contribution can be made. Even if the rate fluctuates, it will be affected only by the difference in change in each wavelength, and thus it will be less susceptible to measurement errors due to the contribution rate fluctuation. Therefore, the temperature of the object to be measured heated in the furnace can be smoothly radiatively measured as an accurate temperature without the influence of stray light noise.

Further, according to the radiation thermometer according to the present invention, auxiliary means such as a shielding plate and a stray light noise source temperature measuring device are not required, and the measurement operation can be performed using one radiation thermometer. You can Therefore, the structure of the apparatus is simplified, and the scope of application is not restricted by the type and method of the furnace.

[0019]

EXAMPLES The present invention will be specifically described below based on examples.

FIG. 1 is an explanatory view showing a measuring system of a radiation thermometer according to the present invention. A chopper 6 is installed between the condenser lenses 4 and 5 inside the radiation thermometer 3, and the radiant light incident from the object to be measured is split into two light beams by the semi-transparent mirror 7 and then placed on each front surface. Interference filter 8, 9
Are incident on the detection elements 10 and 11 as light having different wavelengths. Reference numeral 12 is an eyepiece lens. Each detection element 10, 11
The radiation of different wavelengths detected by the
Is converted into a detection signal and is sent to the arithmetic unit 14 to be corrected by the arithmetic mechanism described above to the temperature of the measured object from which the influence of stray light noise has been removed, and finally displayed and recorded on the output unit 15.

Using the above-mentioned radiation thermometer, as detection wavelength regions, λ ₁ : 3.38 to 3.52 μm, λ ₂ : 3.25 to 3.
Two regions of 85 μm were selected to measure the temperature of four kinds of resin-coated metal materials which were heat-treated in the heating furnace. The heating condition is that the temperature of the measured object is 200 to 300.
C. and the furnace wall temperature were set in the range of 300 to 400.degree. The emissivity (ε ₁ , ε ₂ ) and temperature measurement error at each temperature obtained are shown in Tables 1 and 2. The temperature measurement error is the emissivity ε
₁ = 0.59, shown as a temperature difference at constant conditions of epsilon ₂ = 0.44.

From the results of Tables 1 and 2, it was confirmed that the temperature measurement error due to the influence of the furnace wall temperature was within 2 ° C., and the error factor associated with stray light noise was effectively removed. The error that occurs as an absolute value is due to the effect of emissivity and is independent of the furnace wall temperature.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

As described above, according to the present invention, the radiation temperature measuring method for an in-reactor object capable of removing the influence of the stray light noise component without using auxiliary means and always performing accurate temperature measurement, and this radiation measuring method. It is possible to provide a radiation thermometer having a simple structure that is effective for the temperature method. Therefore, it is extremely useful when applied to temperature control of various furnace operations.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a measuring system of a radiation thermometer according to the present invention.

FIG. 2 is an explanatory diagram showing an incident state at the time of performing radiation temperature measurement of an in-furnace object.

[Explanation of symbols]

 1 heating furnace 2 object to be measured 3 radiation thermometer 4 condenser lens 5 condenser lens 6 chopper 7 semi-transparent mirror 8 interference filter 9 interference filter 10 detector element 11 detector element 12 eyepiece lens 13 preamplifier 14 arithmetic unit 15 output device

Claims (2)

[Claims] 1. A correction coefficient C that detects thermal radiation from an object to be measured at two different wavelengths and changes the characteristic functions f ₁ (T) and f ₂ (T) of each detection signal with respect to the black body temperature depending on the temperature.
Using (T), C (T) · f ₁ (T) = f ₂ (T),
By using this relationship, each detected signal is solved by setting two equations expressed as the sum of the signal component emitted by the measured object and the stray light noise component from the inside of the furnace as C (T) = 1, and the measured object And the assumed temperatures Ts and Tw of the stray light noise component are calculated, the correction coefficients C (Ts) and C (Tw) corresponding to the respective temperatures are calculated, and the expression of the detection signal is calculated using the obtained calculated values. A radiation temperature measuring method of the temperature in a furnace, which is characterized by obtaining the temperature of an object to be measured by removing the influence of stray light noise by solving. 2. The temperature of the object to be measured by the method according to claim 1, from a radiation thermometer of a detection mechanism for separately detecting thermal radiation from the object to be measured at two different wavelengths, and detection signals of the radiation thermometer. Radiation temperature measuring device for in-furnace objects consisting of a computing device for determining