JP5476189B2 - Metal plate temperature measuring device - Google Patents

Description

  The present invention relates to a metal plate temperature measuring device that is used in, for example, a continuous annealing facility or an alloyed hot dip galvanizing facility and measures the temperature of the metal plate in a non-contact manner.

  In continuous annealing equipment for continuously heat-treating steel sheets and galvannealed equipment for galvanizing after hot-dip plating, various types of steel sheets are continuously processed. For this reason, in order to stabilize the mechanical properties (strength, elongation, etc.) and plating properties (degree of alloying, etc.) of steel plates that differ for each product type, the steel plate temperature after the heat treatment process with heating / cooling is set to the target temperature. It is important to control accurately.

  In general, the temperature of a steel sheet continuously conveyed in these facilities is measured using a non-contact radiation thermometer. When using a radiation thermometer, it is necessary to set the emissivity of the steel sheet that is the object to be measured. However, since the emissivity of a steel sheet varies depending on various factors such as the steel sheet itself, the physical properties of the steel sheet, such as the surface properties, and the temperature of the steel sheet, it is very difficult to set the emissivity of the steel sheet in response to such variations. Have difficulty. As a result, an error is likely to occur in the measurement of the steel plate temperature, and the steel plate temperature cannot be accurately controlled to the target temperature.

  Therefore, as a measurement method that eliminates the influence of the emissivity fluctuation of the steel plate as much as possible, the number of times of alternately reflecting between the reference plate and the steel plate is radiated toward the steel plate at an angle of 1 or 2 each. A measuring method based on the knowledge that the apparent emissivity is increased by installing a thermometer has been proposed.

For example, as shown in FIG. 5, a 2000 mm × 600 mm reference plate 102 provided with a temperature control device 105 is placed in a furnace surrounded by a furnace wall so as to face the steel plate 101 to be measured. The target temperature T _{0 of the} steel plate 101 to be measured is input to the temperature control device 105, and power is supplied from the heater power source 104 to the heater 103 built in the reference plate 102 in accordance with an instruction from the temperature control device 105. Further, the temperature T ₂ of the reference plate 102 is directly measured by the contact thermometer 106. Further, the reference plate 102 is opposed to the measured steel plate 101 such that the number of times the radiant energy is alternately reflected between the reference plate 102 and the measured steel plate 101 (interval h = 125 mm) is once or twice. A radiation thermometer 107 is installed toward the steel plate 101 to be measured at an angle θ = 30 ° from the outside of the surface. In this way, the emissivity emitted from the steel plate 101 to be measured is measured by the radiation thermometer 107, and the temperature obtained by converting to the temperature of the black body that emits energy equivalent to this emissivity is the emissivity temperature T. _g . As the temperature _{T 2} of the reference plate 102 and the id temperature _{T g} match, and controls the heater 103 in a temperature controlled device 105, the steel sheet temperature based on the temperature _{T 2} of the reference plate 102 and the id temperature _{T g} This is a steel plate temperature measurement method in which the calculator 109 calculates the temperature T _{1 of the} steel plate 101 to be measured (see, for example, Patent Document 1).

JP 2008-32485 A

  However, the radiation thermometer 107 is opposed to the measured steel plate 101 of the reference plate 102 so that the number of times that the radiant energy is alternately reflected between the reference plate 102 and the measured steel plate 101 is once or twice, respectively. The point on the measured steel plate 101 for measuring the emissivity emitted from the measured steel plate 101 (hereinafter referred to as “ejectivity measurement”). Point)) is away from the center of the opposing reference plate 102. Therefore, it is apt to be affected by background radiation. That is, there is a problem that a view factor F described later tends to be smaller than 1, and a temperature measurement error of the steel sheet is likely to occur. Further, in order to bring the emissivity measurement point closer to the center of the opposing reference plate 102, the angle θ must be very small. Thus, when the angle θ is reduced, for example, the amount of movement of the emissivity measurement point due to vibration or torsion of the measured steel plate 101 that occurs when the measured steel plate 101 is cooled by spraying a gas jet during rapid quenching is reduced. The effect of background radiation increases. Therefore, there is a problem in that the amount of change in the form factor F is large and a temperature measurement error (ΔT = 16 ° C.) of the steel plate 101 to be measured is likely to occur (see FIG. 6: vibration amplitude received by the steel plate 101 to be measured = ± 20 mm).

  An object of the present invention is to provide a metal plate temperature measuring device that is less susceptible to background radiation caused by vibration and twist of the metal plate to be measured and can reduce temperature measurement errors.

ここに、ｄは前記参照板の前記被測定金属板に対向する面の内側から前記被測定金属板に向けて設置した前記放射温度計の測定口径、ｈは前記参照板と前記被測定金属板との間隙、Ｔ_１は前記金属板温度、Ｔ_３は前記測定口径ｄに対応した前記参照板内の測定孔の温度、ΔＴは許容できる温度測定誤差、θは前記参照板の前記被測定金属板に対向する面と前記放射温度計とのなす角度である。 In order to achieve this object, the invention according to claim 1 of the present invention provides:
A reference plate provided with a temperature control device is installed opposite to the metal plate to be measured, and the temperature of the reference plate (hereinafter referred to as “reference plate temperature”) T ₂ is a thermometer different from the radiation thermometer described later. In addition to direct measurement, a radiation thermometer is installed toward the metal plate to be measured at an angle at which the radiant energy is alternately reflected between the reference plate and the metal plate to be measured once or twice. Te, the measured id emitted from the measured metal plate at the radiation thermometer, a temperature obtained by converting the temperature of a black body that emits the id equivalent energy and id temperature T _g The approximate value T ₁ ′ of T ₁ (hereinafter referred to as “metal plate temperature”) T ₁ is calculated by the following equation (1), and this approximate value T ₁ ′ is calculated as the metal plate temperature T _1. In the metal plate temperature measuring device provided with the metal plate temperature calculation circuit, the reference plate Temperature measurements of the metal plate, wherein the said radiation thermometer toward the measured metal plate at an angle satisfying the following formula (2) from the inner surface facing to a measured metal plate θ is located apparatus.
T ₁ ′ = F [T _g + K (T _g −T ₂ )] (1)
Here, K is a correction coefficient based on estimated values of emissivities of the reference plate and the metal plate to be measured, which are obtained from separate measurements or literature values, and F is the reference plate and the metal plate to be measured. Is a form factor based on each geometrical shape and the positional relationship between the two.

Here, d is a measurement aperture of the radiation thermometer installed from the inside of the surface of the reference plate facing the metal plate to be measured toward the metal plate to be measured, and h is the reference plate and the metal plate to be measured. , T ₁ is the temperature of the metal plate, T ₃ is the temperature of the measurement hole in the reference plate corresponding to the measurement diameter d, ΔT is an allowable temperature measurement error , θ is the metal to be measured of the reference plate It is an angle formed between the surface facing the plate and the radiation thermometer .

ここに、ｄは前記参照板の前記被測定金属板に対向する面の内側から前記被測定金属板に向けて設置した前記放射温度計の測定口径、ｈは前記参照板と前記被測定金属板との間隙、θは前記参照板の前記被測定金属板に対向する面と前記放射温度計とのなす角度である。 The invention according to claim 2 of the present invention is
A reference plate provided with a temperature control device is installed opposite to the metal plate to be measured, and the temperature of the reference plate (hereinafter referred to as “reference plate temperature”) T ₂ is a thermometer different from the radiation thermometer described later. In addition to direct measurement, a radiation thermometer is installed toward the metal plate to be measured at an angle at which the radiant energy is alternately reflected between the reference plate and the metal plate to be measured once or twice. Te, the measured id emitted from the measured metal plate at the radiation thermometer, a temperature obtained by converting the temperature of a black body that emits the id equivalent energy and id temperature T _g The approximate value T ₁ ′ of T ₁ (hereinafter referred to as “metal plate temperature”) T ₁ is calculated by the following equation (1), and this approximate value T ₁ ′ is calculated as the metal plate temperature T _1. In the metal plate temperature measuring device provided with the metal plate temperature calculation circuit, the reference plate Temperature measurements of the metal plate, wherein the said radiation thermometer toward the measured metal plate at an angle satisfying the following formula (3) from the inner surface facing to a measured metal plate θ is located apparatus.
T ₁ ′ = F [T _g + K (T _g −T ₂ )] (1)
Here, K is a correction coefficient based on estimated values of emissivities of the reference plate and the metal plate to be measured, which are obtained from separate measurements or literature values, and F is the reference plate and the metal plate to be measured. Is a form factor based on each geometrical shape and the positional relationship between the two.

Here, d is a measurement aperture of the radiation thermometer installed from the inside of the surface of the reference plate facing the metal plate to be measured toward the metal plate to be measured, and h is the reference plate and the metal plate to be measured. , Θ is an angle formed between the surface of the reference plate facing the metal plate to be measured and the radiation thermometer.

According to the present invention, the radiation thermometer is arranged from the inside of the surface of the reference plate facing the metal plate to be measured toward the metal plate to be measured at an angle θ that satisfies the above formula (2) or formula (3). Therefore, it is possible to bring the emissivity measurement point closer to the center of the opposing reference plate, and it is possible to make it less susceptible to the influence of background radiation due to the vibration and torsion of the metal plate to be measured. It is possible to realize a metal plate temperature measuring device that easily approximates the coefficient F to 1 and can reduce temperature measurement errors.

It is a plate direction cross section and control flow figure for demonstrating schematic structure of the temperature measuring apparatus of the steel plate which concerns on one Embodiment. It is explanatory drawing for demonstrating the temperature measurement error of the steel plate when a vibration generate | occur | produces in the steel plate in the temperature measuring apparatus of the steel plate. It is explanatory drawing for demonstrating the temperature measurement error (in the case of angle (theta) = 20 degrees and 30 degrees) of a steel plate when the vibration as shown in FIG. 2 generate | occur | produces in a steel plate compared with a prior art example. FIG. 5 is an explanatory diagram for explaining the influence of the relationship between the measurement diameter d, the gap h, and the angle θ on the temperature measurement error of the steel plate in the steel plate temperature measurement device. It is a sheet passing direction cross section and control flow figure for demonstrating schematic structure of the temperature measuring apparatus of the conventional steel plate. It is explanatory drawing for demonstrating the temperature measurement error of the steel plate when a vibration generate | occur | produces in the steel plate in the temperature measuring apparatus of the steel plate.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view and a control flow diagram for explaining a schematic configuration of a temperature measuring apparatus for a steel plate according to an embodiment.

In FIG. 1, a 2000 mm × 600 mm reference plate 2 equipped with a temperature control device 5 is placed in a furnace surrounded by a furnace wall so as to face the steel plate 1 to be measured. The target temperature T _{0 of the} steel plate 1 to be measured is input to the temperature control device 5, and power is supplied from the heater power supply 4 to the heater 3 built in the reference plate 2 in accordance with an instruction from the temperature control device 5. Further, the temperature T ₂ of the reference plate 2 is directly measured by the contact thermometer 6. Furthermore, the reference plate 2 is opposed to the measured steel plate 1 so that the number of times the radiant energy is alternately reflected between the reference plate 2 and the measured steel plate 1 (interval h = 125 mm) is once or twice, respectively. The radiation thermometer 7 is installed toward the steel plate 1 to be measured at a predetermined angle θ = 30 ° from the inside of the surface to be measured.

  By installing the radiation thermometer 7 in this way, it is possible to bring the emissivity measurement point closer to the center of the opposing reference plate 2 and the influence of background radiation caused by vibration and twist of the steel plate 1 to be measured. The form factor F approaches 1.

  The measurement principle of the present invention will be described in detail below.

ここに、Ｆ_１２、Ｆ_１３はそれぞれ、鋼板１から参照板２および測定孔、Ｆ_２１、Ｆ_３１はそれぞれ、参照板２および測定孔から鋼板１の形態係数で、それぞれの幾何学的形状および位置関係より求まる値である。上式より参照板２および測定孔の射度Ｇを消去して、鋼板１の射度Ｇ_１を求めると、下記式が得られる。

ここで、Ｆ_２１は１にほぼ等しい場合は、Ｆ_２１＝１とおくことにより簡略化される。また、測定孔は鋼板１の面積に比べ非常に小さい場合、Ｆ_１３＜＜１、ε_３は１に等しいとはいえないものの、１に近いので、１−ε_３＜＜１、したがって上式は下記式に簡略化できる。

鋼板１の射度Ｇ_１とこれと等価なエネルギーを放射する黒体の温度（以下、「射度温度」という）Ｔ_ｇとの間には、Ｇ_１＝σＴ_ｇ ^４の関係があるので、上式より下記式が導かれ、射度温度Ｔ_ｇが算出できることとなる。

The emissivity of the steel plate 1 and the reference plate 2 that are two finite parallel plates and the measurement hole arranged inside the surface of the reference plate 2 is expressed by the following equation when background radiation from the surroundings is ignored. .

Here, F ₁₂ and F ₁₃ are the steel plate 1 to the reference plate 2 and the measurement hole, respectively, and F ₂₁ and F ₃₁ are the shape factors of the reference plate 2 and the measurement hole to the steel plate 1, respectively. This value is obtained from the positional relationship. Clear the id G reference plate 2 and the measurement hole from the above equation, when determining the id G ₁ of the steel plate 1, the following equation is obtained.

Here, when F ₂₁ is substantially equal to 1, it is simplified by setting F ₂₁ = 1. Further, when the measurement hole is very small compared to the area of the steel plate 1, F ₁₃ << 1, ε ₃ is not equal to 1, but is close to 1, so 1-ε ₃ << 1, and thus the above formula Can be simplified to:

Since there is a relationship of G ₁ = σT _g ⁴ between the emissivity G _{1 of the} steel sheet 1 and the temperature T _g of the black body that emits energy equivalent to this (hereinafter referred to as “ejectivity temperature”), formula above equation is led, id temperature T _g is can be calculated.

  Based on the above formula, the following temperature measurement error ΔT will be described in detail.

ただし、

ここで、Ｆは鋼板１と参照板２との幾何学的関係により変動する形態係数であり、１に近づくように設定されている。また、Ｋは、鋼板１および参照板２の放射率ε_１、ε_２のみの関数からなる補正係数である。このため、補正係数Ｋ自体は、鋼板１および参照板２の放射率変動の影響を受けることになるが、参照板２の温度を射度温度Ｔ_ｇに近づくように制御するので、補正係数Ｋによる誤差が除外され高精度の鋼板温度の測定が可能となる。 F ₁₃ can be expressed as a function of θ and d / h, and when the width and length of the reference plate 2 are sufficiently larger than h and d and the temperatures of the steel plate 1 and the reference plate 2 are substantially equal, ε ₁ In the range of ≧ 0.2 and ε ₂ ≧ 0.2, the temperature measurement error ΔT can be approximated by the following equation.

However,

Here, F is a form factor that varies depending on the geometric relationship between the steel plate 1 and the reference plate 2, and is set to approach 1. K is a correction coefficient composed of a function of only the emissivities ε ₁ and ε ₂ of the steel plate 1 and the reference plate 2. Therefore, the correction coefficient K itself, since it will be affected by emissivity variations of the steel sheet 1 and the reference plate 2 is controlled so as to approach the temperature of the reference plate 2 to Id temperature T _g, the correction factor K The error due to the above is excluded, and the steel plate temperature can be measured with high accuracy.

When the approximate value T ₁ ′ calculated by the approximate expression (1) is regarded as the temperature T _{1 of the} steel plate 1 to be measured, the temperature measurement error ΔT is accompanied (details will be described later). However, in the case of the present invention, the emissivity emitted from the steel plate 1 to be measured is measured by the radiation thermometer 7, and the temperature obtained by converting to the temperature of a black body that radiates energy equivalent to this emissivity is obtained. a degree temperature T _g, the id temperature T _g and such that the temperature T ₂ of the reference plate 2 match (i.e., the target temperature T ₀ or the approximate value of the temperature T ₂ is measured steel plate 1 reference plate T ₁ to approach ') controls the heater 3 in a temperature controlled device 5, the above approximate expression with id temperature T _g and the reference plate within the steel sheet temperature calculator 9 based on the temperature T ₂ of 2 (1), An approximate value T ₁ ′ of the temperature T ₁ of the steel plate 1 to be measured is calculated, and the steel plate 1 to be measured of the reference plate 2 is a temperature measuring device for the steel plate 1 that regards this approximate value T ₁ ′ as the temperature T ₁ of the steel plate 1 A radiation thermometer 7 is arranged from the inside of the surface facing 1 toward the steel sheet 1 to be measured at a predetermined angle θ. Since it is configured to be, it is possible to reduce the above-described temperature measurement error [Delta] T (the details of which will be described later). Therefore, even when the steel plate 1 to be measured is subjected to vibration or torsion, a steel plate temperature measuring device that is less affected by background radiation due to vibration or torsion of the steel plate 1 to be measured and can reduce temperature measurement errors is realized. (Refer to FIG. 2: Vibration amplitude received by the steel plate 1 to be measured = ± 20 mm). As shown in FIG. 2, the temperature measurement error ΔT is 3 ° C., which is about 1/5 of the temperature measurement error ΔT = 16 ° C. in the conventional example (see FIG. 6). The contact-type thermometer 6 for measuring the temperature of the reference plate 2, a plurality placed on reference plate 2, it is desirable that the reference plate temperature T ₂ by averaging the measured values of the contact thermometer 6.

  FIG. 3 is an explanatory diagram for explaining the temperature measurement error (when the angle θ = 20 °, 30 °) of the steel plate 1 when vibration as shown in FIG. 2 occurs in the steel plate 1 in comparison with the conventional example. It is. In the case of the embodiment (invention example) of the present invention, it can be seen that the temperature measurement error of the steel sheet 1 is further reduced when the angle θ changes from 30 ° to 20 °. However, in the case of the conventional example, the reduction effect is not recognized so much. In the case of the conventional example, even if the angle θ is larger than 30 ° or smaller than 20 °, the temperature measurement error of the steel plate 1 is caused by the influence of the background radiation caused by the vibration and torsion of the steel plate 1 to be measured. Reduction cannot be expected.

さらに、上式を変形すると、下記式（２）となる。

例えば、被測定鋼板１の温度範囲が２００℃〜６００℃、測定孔温度が５０℃〜１００℃、許容できる温度測定誤差ΔＴが１℃以下(例えば、放射温度計７の測定温度の再現性と同等と設定する)とすると、上記式（２）は下式（３）で表わすことができる。

ただし、Ｔ_１−Ｔ_３が大きいほどθの範囲は小さくなるため、Ｔ_１−Ｔ_３が最大となる条件を選択した。上例の場合、Ｔ_１＝６００℃、Ｔ_３＝５０℃である。 FIG. 4 shows the metal plate temperature T ₁ , the temperature T ₃ of the measurement hole in the reference plate 2 corresponding to the measurement diameter d, the measurement diameter d, and the gap h when the steel plate 1 is stationary in this embodiment. It is explanatory drawing for demonstrating the influence which the relationship of angle (theta) has on temperature measurement error (DELTA) T of the steel plate. As shown in FIG. 4, the temperature measurement error ΔT of the steel sheet 1 becomes smaller as the line A → the line B → the line C → the line D → the line E. At this time, the relationship between the metal plate temperature T ₁ , the temperature T ₃ of the measurement hole in the reference plate 2 corresponding to the measurement diameter d, the measurement diameter d, the gap h, and the angle θ gives an acceptable temperature measurement error ΔT of the steel sheet 1. The influence is shown by the following equation in which the above equation (4) is modified and θ is expressed as a function of T ₁ , T ₃ , ΔT, and d / h.

Furthermore, when the above equation is modified, the following equation (2) is obtained.

For example, the temperature range of the steel plate 1 to be measured is 200 ° C. to 600 ° C., the measurement hole temperature is 50 ° C. to 100 ° C., and the allowable temperature measurement error ΔT is 1 ° C. or less (for example, the reproducibility of the measurement temperature of the radiation thermometer 7 Assuming that they are equivalent), the above equation (2) can be expressed by the following equation (3).

However, since the range of θ becomes smaller as T ₁ -T ₃ becomes larger, a condition that maximizes T ₁ -T ₃ was selected. In the case of the above example, T ₁ = 600 ° C. and T ₃ = 50 ° C.

  Therefore, if the measurement diameter d and the gap h are set so as to satisfy the above-described formula (3), the temperature measurement error ΔT of the steel plate 1 when the steel plate 1 is stationary is 1 ° C. or less. Incidentally, in the case of the example of the measurement aperture d = 30 mm, the gap h = 125 mm, the angle θ = 20 °, and 30 ° described in the present embodiment, the temperature measurement error ΔT of the steel plate 1 when the steel plate 1 is stationary. Is 1 ° C. or lower.

  Thus, if the technical idea of the present invention is adopted, the temperature measurement error of the steel plate 1 when the steel plate 1 shown in FIG. 4 is stationary and the steel plate when the steel plate 1 shown in FIG. It can be seen that the temperature measurement error can be realized by adding the temperature measurement errors of 1 and is less susceptible to the background radiation caused by the vibration of the steel plate 1 to be measured, and can reduce the temperature measurement error. Although the example in which the steel plate 1 to be measured has been described has been described, the present invention is not limited to this. For example, the technical idea of the present invention can be applied even when the steel plate 1 to be measured is twisted.

  In the present embodiment, the steel plate is used as the metal plate to be measured. However, the present invention is not limited to this and can be widely applied to the metal plate.

1: Steel plate 2: Reference plate 3: Heater
4: Heater power supply 5: Temperature controller 6: Contact thermometer 7: Radiation thermometer 9: Steel plate temperature calculator

Claims (2)

A reference plate provided with a temperature control device is installed opposite to the metal plate to be measured, and the temperature of the reference plate (hereinafter referred to as “reference plate temperature”) T ₂ is a thermometer different from the radiation thermometer described later. In addition to direct measurement, a radiation thermometer is installed toward the metal plate to be measured at an angle at which the radiant energy is alternately reflected between the reference plate and the metal plate to be measured once or twice. Te, the measured id emitted from the measured metal plate at the radiation thermometer, a temperature obtained by converting the temperature of a black body that emits the id equivalent energy and id temperature T _g The approximate value T ₁ ′ of T ₁ (hereinafter referred to as “metal plate temperature”) T ₁ is calculated by the following equation (1), and this approximate value T ₁ ′ is calculated as the metal plate temperature T _1. In the metal plate temperature measuring device provided with the metal plate temperature calculation circuit, the reference plate Temperature measurements of the metal plate, wherein the said radiation thermometer toward the measured metal plate at an angle satisfying the following formula (2) from the inner surface facing to a measured metal plate θ is located apparatus.
T ₁ ′ = F [T _g + K (T _g −T ₂ )] (1)
Here, K is a correction coefficient based on estimated values of emissivities of the reference plate and the metal plate to be measured, which are obtained from separate measurements or literature values, and F is the reference plate and the metal plate to be measured. Is a form factor based on each geometrical shape and the positional relationship between the two.

Here, d is a measurement aperture of the radiation thermometer installed from the inside of the surface of the reference plate facing the metal plate to be measured toward the metal plate to be measured, and h is the reference plate and the metal plate to be measured. , T ₁ is the temperature of the metal plate, T ₃ is the temperature of the measurement hole in the reference plate corresponding to the measurement diameter d, ΔT is an allowable temperature measurement error , θ is the metal to be measured of the reference plate It is an angle formed between the surface facing the plate and the radiation thermometer . A reference plate provided with a temperature control device is installed opposite to the metal plate to be measured, and the temperature of the reference plate (hereinafter referred to as “reference plate temperature”) T ₂ is a thermometer different from the radiation thermometer described later. In addition to direct measurement, a radiation thermometer is installed toward the metal plate to be measured at an angle at which the radiant energy is alternately reflected between the reference plate and the metal plate to be measured once or twice. Te, the measured id emitted from the measured metal plate at the radiation thermometer, a temperature obtained by converting the temperature of a black body that emits the id equivalent energy and id temperature T _g The approximate value T ₁ ′ of T ₁ (hereinafter referred to as “metal plate temperature”) T ₁ is calculated by the following equation (1), and this approximate value T ₁ ′ is calculated as the metal plate temperature T _1. In the metal plate temperature measuring device provided with the metal plate temperature calculation circuit, the reference plate Temperature measurements of the metal plate, wherein the said radiation thermometer toward the measured metal plate at an angle satisfying the following formula (3) from the inner surface facing to a measured metal plate θ is located apparatus.
T ₁ ′ = F [T _g + K (T _g −T ₂ )] (1)
Here, K is a correction coefficient based on estimated values of emissivities of the reference plate and the metal plate to be measured, which are obtained from separate measurements or literature values, and F is the reference plate and the metal plate to be measured. Is a form factor based on each geometrical shape and the positional relationship between the two.

Here, d is a measurement aperture of the radiation thermometer installed from the inside of the surface of the reference plate facing the metal plate to be measured toward the metal plate to be measured, and h is the reference plate and the metal plate to be measured. , Θ is an angle formed between the surface of the reference plate facing the metal plate to be measured and the radiation thermometer.

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