JPS6225973B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation thermometer that measures the temperature of an object by removing the influence of emissivity.

Conventional radiation thermometers include monochromatic thermometers that measure the temperature of an object based on the amount of radiant energy from the object, and two different types.
There were two-color thermometers that determined the temperature of an object from the ratio of spectral radiant energies of wavelengths. These radiation thermometers can only measure the true temperature of a black body in the case of a monochrome thermometer, and only a gray body in the case of a two-color thermometer, and the influence of emissivity cannot be removed for ordinary objects, which is a major problem. It was hot.

In view of the above points, it is an object of the present invention to provide a radiation thermometer that can measure the surface temperature of an ordinary object while eliminating the influence of emissivity.

The principle of this invention will be explained with reference to FIG. In the figure, 1 indicates an object to be measured with temperature T and emissivity ε, and 2
is set at a predetermined distance l from the object to be measured 1, and is the temperature at which radiant energy is emitted to the object to be measured 1.
A comparative hot plate with Tc and emissivity εc, 3 detects the radiant energy emitted by the object to be measured 1 itself through the opening 2a of the comparative hot plate 2, and the radiant energy of the comparative hot plate 2 reflected from the object to be measured 1. It is a radiation detector.

When the wavelength λ and the temperature T, the spectral radiant energy luminance emitted from the black body is L(λ, T), and the object to be measured 1
When the distance between and the comparison hot plate 2 is l, the radiation detector 3
If the output signal of is e(l), then the following equation holds true when the distance l ₁ is assumed that the emissivity εc of the comparison hot plate 2 is sufficiently close to 1.

e(l ₁ )=ε・L(λ,T)+εc(1−ε)L(λ,Tc)・f(l ₁ )...(1) The first term on the right side of equation (1) is the object to be measured. The contribution of the radiant energy emitted by 1 itself, the second term is the radiant energy εcL (λ, Tc) emitted from the comparative hot plate 2
is the contribution of the radiation energy reflected by the object to be measured and incident on the radiation detector 3, and f(l ₁ ) is the contribution of the radiation energy from the comparison hot plate 2 reflected by the object to be measured 1 and incident on the radiation detector 3. This is a shape factor indicating the incidence rate.

Next, if the distance between the object to be measured 1 and the comparison hot plate 2 is _l2 , then the following equation holds true.

e(l ₂ )=ε・L(λ,T)+εc(1−ε)L(λ,Tc)・f(l ₂ )...(2) Subtracting equation (2) from equation (1) gives e (l ₁ )−e(l ₂ )=εc(1−ε)・L(λ,Tc)・{f(l ₁ )−f(l ₂ ) ……(3) Therefore, 1−ε =e(l ₁ )−e(l ₂ )/εc·L(λ, Tc)·{f(l ₁ )−f(l ₂ )} (4). On this right-hand side, e(l ₁ ) - e(l ₂ ) is a measurable quantity, and εc, L(λ, Tc) are known quantities, so f(l ₁ ) - f(l ₂ ) is a measurable quantity. If it's on,
Emissivity ε can be found from equation (4). The obtained emissivity ε is (1)
By substituting into the equation or equation (2), the temperature T of the object to be measured 1 can be found at all times.

Note that the shape factor f(l) is a quantity that depends only on the geometrical shapes of the object to be measured 1 and the comparison hot plate 2, and their mutual positional relationship, so it may be determined in advance by measurement.

By the way, when the specularity of the object to be measured 1 changes, the shape factor f(l) changes with respect to the distance l as shown in FIG. 2. In other words, as the specularity increases, it shifts to the right. In other words, in the case of a metal such as a steel plate with strong specularity, as shown in the curve shown in FIG. It becomes 1. Therefore, when the comparison heating plate 2 is brought close to the object to be measured 1, the output when the change in the output signal of the radiation detector 3 becomes zero is e', and by removing the comparison heating plate 2, etc. If the output of the radiation detector 3 in the absence of that influence is set to e ₀ , then the following equation holds true.

e′=ε・L(λ,T) +εc・(1−ε)・L(λ,Tc) ……(5) e ₀ =ε・L(λ,T) ……(6) From this, e′ −e ₀ = εc・(1−ε)・L(λ, Tc) ……(7) Therefore, 1−ε=e′−e ₀ /εc・L(λ, Tc) ……(8) Become. In this equation (8), since the right side is a measurable or known quantity, the emissivity ε can be found, and by substituting this into equation (6), the temperature T of the object to be measured can be found.

In addition, in order to be able to ignore the influence of the comparative heating plate 2, the distance l between the comparative heating plate and the object to be measured should be set sufficiently large, the comparative heating plate should be deviated laterally from the measuring optical axis, or the comparative heating plate should be deviated from the measuring optical axis. Either method may be used, such as by placing the plate facing upward or by placing a lid on the comparative heating plate.

FIG. 3 is a configuration explanatory diagram showing a more specific embodiment of the present invention. In the figure, the object to be measured 1
On the other hand, the comparison heating plate 2 can be moved obliquely at a certain angle θ, and the radiation detector 3 can be moved from the object to be measured 1 through the aperture 2a located off the center of the comparison heating plate 2. It has become possible to detect the radiant energy of Further, the distance l between the comparative hot plate 2 and the object to be measured 1 can be changed by a drive mechanism (not shown), and if necessary, it can be moved to the side in the B direction to eliminate the influence of this. . Further, a heater H is provided on the comparative heat plate 2, and its temperature Tc is detected by a temperature detector D such as a thermocouple.
is detected, and the temperature controller 4 controls the heater H to control its temperature. Then, the position signal of the comparative heat plate 2, the temperature signal Tc, and the output signal e(l) of the radiation detector 3 are inputted to a calculation unit 5 such as a microcomputer, and the temperature T of the object to be measured 1 as described above is Control of the movement of the comparison hot plate 2 for measuring the temperature and calculation processing are performed, and output signals T, ε, etc. can be taken out from the output terminal 6. Note that all the processing of the temperature control section 4 may be performed by the calculation section 5.

As described above, the present invention is a radiation temperature sensor that performs arithmetic processing based on the change in the output signal of the radiation detector when the comparative heat plate is moved, and measures the emissivity and temperature of the object to be measured. It is a total.

Therefore, the influence of the emissivity of the object to be measured can be removed to measure the correct temperature, and even if the emissivity fluctuates, corrections can be made automatically, so it is suitable for always on-line measurements. The temperature of a moving object can also be easily measured. In addition, in the case of metal plates with strong specularity such as steel plates, the distance between the object to be measured and the comparison hot plate can be made sufficiently large, so when measuring running steel plates, etc., fluctuations such as vertical vibrations of the object to be measured can be avoided. Measurements can be made safely even when In addition, since it is not an equilibrium method in which the temperature of the comparison hot plate is matched with the temperature of the object to be measured, high-speed response is possible. Also, any type of radiation detector may be used,
It has excellent effects such as being able to output emissivity and temperature simultaneously.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the principle of this invention, Figure 2 is
FIG. 3, a relational diagram for explaining the operation, is a configuration explanatory diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Measurement object, 2...Comparison hot plate, 3...Radiation detector, 5...Calculating section.

Claims (1)

[Claims] 1. A comparative heating plate that emits radiant energy to an object to be measured, a radiation detector that detects radiant energy emitted by the object to be measured itself and radiant energy of the comparative heating plate reflected from the object to be measured, and Calculate the emissivity of the object to be measured from the difference between the output of the radiation detector when the hot plate is brought close to the object to be measured and the output of the radiation detector when there is no influence from the comparative hot plate, and use this emissivity. A radiation thermometer characterized by comprising a calculation section that measures the temperature of an object to be measured.