JPH0579920A - Dichromic radiation temperature measuring method and dichromic radiation thermometer - Google Patents

Abstract

PURPOSE:To prevent the occurrence of measurement errors by setting the fluctuation ranges of emissivities to physically and actually acceptable specific limit ranges. CONSTITUTION:A radiometer detector makes spectral diffraction with two interference filters transmitting the light in different wavelength bands, for example, and it detects two spectral radiation intensity signals with two detectors. An arithmetic processing device calculates the temperature of a measured object with these signals and various parameters inputted from an input section in advance, and it outputs the calculated result. Relations between the first and second spectral emissivities epsilon1, epsilon2 in different wavelength bands are set as shown in equations, where epsilon1min is the minimum set value of the first spectral emissivity, epsilon1max is the maximum set value, epsilonmin<=epsilon1max, and R is a constant (emissivity ratio). When the temperature of the object is measured from two corresponding spectral radiation intensity signals, no abnormal emissivity value is erroneously determined even if noise is mixed in the spectral radiation intensity signals, and the temperature can be measured with less error.

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 technique for measuring the temperature of an object in a non-contact manner in a process such as the steel industry or in an experimental research field in a university or the like.

[0002]

2. Description of the Related Art Since a radiation thermometer can measure the temperature of an object in a non-contact manner, it is used in a wide range of industrial and academic research as a means for measuring the temperature of a high-temperature object, a high-speed moving object and the like. However, the most commonly used monochromatic radiation thermometer has a problem that the temperature measurement error due to the difference between the emissivity set value and the true emissivity of the object becomes large when applied to an object whose emissivity fluctuates. ..

On the other hand, a two-color radiation thermometer, which attempts to measure the temperature of an object by assuming a proportional relationship between spectral emissivities in two different wavelength bands, is widely used as an alternative means of a monochromatic thermometer, The temperature of the object is obtained by applying a simple proportional relationship ε ₂ = R · ε ₁ (1) between the first spectral emissivity ε ₁ and the second spectral emissivity ε ₂ .

However, according to this method, when noise is mixed in the spectral radiance signal during measurement of an object having a low emissivity such as aluminum, or when the signal drifts during measurement near the lower limit of the measurement temperature range, this method is actually used. In some cases, an extremely low emissivity value is calculated, resulting in an abnormally large temperature measurement error.On the contrary, when an abnormally high emissivity value is calculated, a large temperature measurement error occurs. It may happen. Further, when the two true emissivities deviate from the relationship expressed by the equation (1) like the object to be measured that is encountered in the actual industrial process, a large measurement error often occurs. Yes, it is a serious problem.

This is a problem that occurs because the first and second emissivities are not subject to the physically or practically permissible limiting range, and is a serious problem in measurement in industrial processes and the like. ing.

[0006]

SUMMARY OF THE INVENTION The present invention provides a two-color radiation temperature measuring method which does not cause the above-mentioned measurement error by setting a limit range in which the emissivity is physically or practically recognized. And a two-color radiation thermometer.

[0007]

According to the present invention, for two spectral emissivities in different wavelength bands, the relational expression between the first spectral emissivity ε ₁ and the second spectral emissivity ε ₂ is ε _2. = R · ε _1min 0 ≦ ε ₁ <ε _1min ε ₂ = R · ε ₁ ε _1min ≦ ε ₁ <ε _1max ε ₂ = R · ε _1max ε _1max ≦ ε ₁ ≦ 1 where ε _1min : the first spectrum The minimum set value of emissivity ε _1max : the maximum set value of the first spectral emissivity R: As a constant (emissivity ratio), the temperature of the object is measured from two corresponding spectral radiance signals. Color radiation thermometry.

The invention further provides a dichroic radiometer detector for detecting the spectral radiance in two different spectral bands, the spectral radiance signals transmitted by the radiometer detector and their corresponding spectral radiances. The relational expression between the rates is ε ₂ = R ・ ε _1min 0 ≦ ε ₁ <ε _1min ε ₂ = R ・ ε ₁ ε _1min ≦ ε ₁ <ε _1max ε ₂ = R ・ ε _1max ε _1max ≦ ε ₁ ≦ 1 where , Ε _1min : minimum set value of the first spectral emissivity ε _1max : maximum set value of the first spectral emissivity ε _1min <ε _1max , an arithmetic processing unit for calculating the temperature of the object, and the radiometer detector _And a means for inputting the coefficients R, ε _{1m in} , ε _1max representing the relational expression of the first term and the means for outputting the temperature value obtained by the calculation. It is a two-color radiation thermometer.

[0009]

[Function] Spectral radiance (L ₁ , L ₂ ) in different wavelength bands (center wavelengths λ ₁ , λ ₂ ) of thermal radiation from an object
Is detected. The spectral blackbody radiance is represented by the Wien equation L _b (λ, T) = K · exp (−C ₂ / λ · T) (2) where K is a constant C ₂ : a second constant of radiation (= 14, 388 (μm · K)) λ: Detection wavelength (μm) T: When expressed in temperature (K), (L ₁ , L ₂ ) is L ₁ = ε ₁₀ · K ₁ · exp (-C ₂ / λ ₁ · T ₀ ) ... (3) L ₂ = ε ₂₀ · K ₂ · exp (-C ₂ / λ ₂ · T ₀ ) ... (4)

However, ε ₁₀ and ε ₂₀ : true spectral emissivity T ₀ : true temperature The assumed temperature of the object is T when the true temperature and the emissivity are unknown.
Then, similarly to the equations (3) and (4), L ₁ = ε ₁ · K ₁ · exp (-C ₂ / λ ₁ · T) ... (5) L ₂ = ε ₂ · K ₂ · exp (-C ₂ / λ ₂ · T) (6) holds.

However, ε ₁ , ε ₂ : apparent spectral emissivity T ₀ : assumed temperature When the equations (3) to (6) are rearranged, the apparent emissivity and the true emissivity when the assumed temperature T is changed. The relationship of emissivity is calculated as the following equation.

Ε ₂ = ε ₂₀ · (ε ₁ / ε ₁₀ ) ... (7) FIG. 1 shows that when the true emissivity (ε ₁₀ , ε ₂₀ ) changes,
It is a group of curves showing the relationship between the apparent emissivities (ε ₁ , ε ₂ ) expressed by the equation (7).

It is assumed that certain measured values (L ₁ , L ₂ ) are obtained, and the true emissivity at that time is marked with a circle in FIG. At this time, the assumed temperature T is the true temperature T. If they are equal to (5), (6)
The apparent emissivity calculated by the formula is equal to the true emissivity,
If the assumed temperature is lower than the true temperature, the apparent emissivity moves to the upper right along the curve, and if the assumed temperature is higher than the true temperature, the apparent emissivity moves to the lower left toward the curve. Reach the origin (0,0) (T = ∞).

Now, the relational expression of the equation (1) used in the conventional two-color radiation thermometry is shown together with the curve group showing the relation between the apparent emissivities shown in FIG. It is FIG. Similar to the above, certain measured values (L ₁ , L ₂ ) are obtained, and the true emissivity at that time is represented by the ● mark in FIG. 2 and is the two-color radiation thermometry method represented by the formula (1). Suppose that the assumption of is satisfied. At this time, the assumed temperature T is the true temperature T. The apparent emissivity obtained by the equations (5) and (6) is equal to the true emissivity and can be obtained as a solution to satisfy the equation (1). This is the principle of conventional two-color radiation thermometry.

If, while measuring the signal from the object having the true emissivity represented by the mark ●, L ₁ is measured 32% lower due to the inclusion of some noise such as electrical and optical, then Apparent emissivity of moves to the point indicated by ▲. Therefore, the solution obtained by the conventional two-color method is ▲
The point marked with ■ is the intersection of the curve corresponding to the formula (7) passing through the mark and the straight line represented by the principle formula (1). The emissivity at the points marked with ■ in the figure is much smaller than the true emissivity point ● and gives a value that is so small that it cannot actually occur, so the obtained temperature value must be extremely higher than the true temperature. Absent.

On the contrary, even when noise is mixed in the spectral radiance signal when the true emissivity is high, an emissivity value that is unrealistically high and a temperature considerably lower than the true temperature are obtained. The value may be obtained.

As described above, the emissivity value which cannot be actually obtained (for example, 0.003 or 0.999, which is abnormally too low or too high), and thus a temperature measurement value including a large error is obtained. The reason is that the conventional two-color temperature measuring method occurs simply because the mathematical principle formula (1) is used, and it does not consider the fluctuation range of the emissivity observed in the actual object. caused by.

In the method of the present invention, such a measurement error can be eliminated by setting the limit value recognized in the actual object in the variation range of the emissivity. That is, for example, it is considered to measure a cold rolled steel sheet in a continuous annealing furnace which is one of steel processes. Since the steel sheet is oxidized in the furnace, the emissivity is about 0.2 to 0.85.
Ε ₂ = R · 0.20 0 ≦ ε ₁ <0.20 ε ₂ = R · ε ₁ 0.20 ≦ ε ₁ <0.85 ε ₂ = R · 0.85 0.85 ≦ If ε ₁ ≦ 1 is measured, the drawbacks of the conventional method can be eliminated. Of course, the emissivity ratio R may be adjusted to an optimum value according to the measurement target, as in the conventional method.

In this way, even if noise is mixed in the spectral radiance signal, as described above, the emissivity value that is abnormally too low or too high will not be erroneously stopped.
It is possible to measure with less temperature measurement error. An example under the same conditions as those shown in FIG. 2 will be shown using FIG.

When measuring a signal from an object having a true emissivity represented by a mark ●, L ₁ is measured 32% lower because noise such as electric or optical is mixed therein. Apparent emissivity of moves to the point indicated by ▲. Now, if the first set values ε _1min and ε _{1max of the emissivity} are 0.35 and 0.8, respectively, since the lower limit value of the emissivity is set in the method of the present invention, the solution of the emissivity is determined. Is obtained as a point indicated by a circle, and therefore, it is possible to measure with a remarkably small error as compared with the conventional method.

[0021]

EXAMPLE FIG. 4 shows a structural example of a temperature measuring device according to the method of the present invention. The radiometer detector 1 detects two spectral radiance signals at different wavelengths, which are transmitted to the processor 2. The arithmetic processing unit calculates the temperature of the object by using two spectral radiance signals and various parameters input from the input unit 3 such as a keyboard in advance, and outputs the calculation result from the output unit 4. Radiometer detector 1
Can be easily configured by using, for example, two interference filters that transmit light of different wavelength bands to perform spectral analysis and use two detectors for detecting the transmitted light.

FIG. 5 is a diagram showing the relationship between two emissivities when applied to the temperature measurement of a surface-treated steel sheet. The relationship between the spectral emissivities at the wavelengths of 2.2 μm and 1.6 μm can be regarded as a proportional relationship of approximately 1.0 in the range of the emissivity at the wavelength of 2.2 μm from 0.13 to 0.7. Therefore, assuming that the spectral emissivities at the wavelengths of 2.2 μm and 1.6 μm are ε ₁ and ε ₂ , respectively, ε ₂ = 0.35 0 ≦ ε ₁ <0.35 ε ₂ = ε ₁ 0.35 ≦ ε By expressing ₁ <0.80 ε ₂ = 0.80 0.80 ≤ ε ₁ ≤ 1, it was possible to perform temperature measurement with a small measurement error due to a noise signal or the like.

[0023]

According to the present invention, the emissivity variation range of the object to be measured is limited to a realistic range for calculation, and temperature measurement with a small error becomes possible. When measuring the radiation temperature in an industrial process or the like in which a noise signal is mixed with an electrical or optical detection signal, by using the method and apparatus according to the present invention, it is unrealistically too low or too high. It is possible to prevent an error in obtaining the emissivity value and the economic effect is great.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between apparent emissivities.

FIG. 2 is a diagram showing a method of obtaining a solution of a conventional two-color radiation thermometry.

FIG. 3 is a diagram showing how to obtain a solution by the method of the present invention.

FIG. 4 is a diagram showing a configuration example of a temperature measuring device according to the present invention.

FIG. 5 is a diagram showing an example of a relationship between spectral emissivities according to the present invention.

[Explanation of symbols]

 1 Radiometer detector 2 Arithmetic processing unit 3 Parameter input section for arithmetic 4 Output section of arithmetic result etc.

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[Procedure amendment]

[Submission date] September 12, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

However, ε ₁ , ε ₂ : apparent spectral emissivity T : assumed temperature When the formulas (3) to (6) are rearranged, the apparent emissivity and the true radiation when the assumed temperature T is changed. The relationship between the rates is calculated as the following equation.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Ε₂ = Ε₂₀・(Ε₁ / Ε_Ten) ^λ1^{/ Λ}2 (7) Figure 1 shows the true emissivity (ε_Ten, Ε₂₀) Changes,
Apparent emissivity (ε₁ , Ε₂ )Among
It is a group of curves showing the relationship.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

If L ₁ is measured 32% lower due to the inclusion of some noise such as electrical or optical during measurement of a signal from an object having a true emissivity represented by a ● mark, then Apparent emissivity of moves to the point indicated by ▲. Now, the first set values of emissivity ε _1min , ε
_1max is assumed to be a 0.35,0.8 each
Since the lower limit value of the emissivity is set in the method of the present invention, the solution of the emissivity is obtained as a point indicated by a circle, and therefore, the measurement with a remarkably small error is possible as compared with the conventional method. Become.

Claims (2)

[Claims] 1. A first spectral emissivity ε ₁ and a second spectral emissivity ε for two spectral emissivities in different wavelength bands.
The relational expression between ₂ is ε ₂ = R · ε _1min 0 ≦ ε ₁ <ε _1min ε ₂ = R · ε ₁ ε _1min ≦ ε ₁ <ε _1max ε ₂ = R · ε _1max ε _1max ≦ ε ₁ ≦ 1 Where ε _{1min is} the minimum set value of the first spectral emissivity, ε _{1max is} the maximum set value of the first spectral emissivity, R is a constant (emissivity ratio), and the temperature of the object is calculated from the corresponding two spectral radiance signals. A two-color radiation thermometer characterized by measuring. 2. A dichroic radiometer detector for detecting spectral radiance in two different spectral bands, and between the spectral radiance signals transmitted from the radiometer detector and their corresponding spectral emissivity. The relational expression is ε ₂ = R ・ ε _1min 0 ≦ ε ₁ <ε _1min ε ₂ = R ・ ε ₁ ε _1min ≦ ε ₁ <ε _1max ε ₂ = R ・ ε _1max ε _1max ≦ ε ₁ ≦ 1 where ε _1min : Minimum setting value of the first spectral emissivity ε _1max : Maximum setting value of the first spectral emissivity ε _1min <ε _1max , an arithmetic processing unit for calculating the temperature of the object, and a black body of the radiometer detector A two-color system comprising means for inputting a furnace calibration curve and coefficients R, ε _1min , ε _1max representing the relational expression of the first term, and means for outputting a temperature value obtained by calculation. Radiation thermometer.