JPS6166131A - Radiation thermometer - Google Patents

Abstract

PURPOSE:To measure the low temperature of a body accurately, by providing a signal fiber, which transmits infrared rays that are emitted from a material to be measured and converged, and a disturbance fiber in parallel, and covering both fibers by an inner cover comprising an excellent heat conducting material and an outer cover comprising a heat insulating material. CONSTITUTION:Infrared rays emitted from a material to be measured 3 are inputted to the front end of a signal fiber 6 through a light converging optical system 2. The front end of a disturbance fiber 9, which is provided in parallel with the fiber 6, is closed by a fixing jig 8. As a material for the jig 8, a non-metallic material such as quartz glass and alumina is used as a heat insulating material. The inner surface is coated by tin, lead o the like. The fibers 6 and 9 are formed into a unitary body by an inner cover 13 having excellent heat conductivity. An outer cover 14 having excellent heat insulation is provided on the outside. The light, which is transmitted by the fibers 6 and 9, are detected by a signal detector 2 and a disturbance detector 11. The signals are processed by a data processor 12, and the temperature of the material to be measured 3 is recorded by a recorder 5. Thus the effect of the disturbance is corrected, and the temperature of the low temperature body can be accurately measured.

Description

[Detailed Description of the Invention] (A) Technical field This invention uses an infrared light transmission fiber to remotely transmit
Related to radiation thermometers that measure temperature.

An object with a finite temperature emits light with a temperature-dependent spectrum and intensity. A radiation thermometer measures the temperature of an object by measuring the intensity of radiation.

Regarding black body radiation, a blank radiant is established.

C7 C, = 3.74-I x 10'' (W-m2)
(2) C2=1.439X10 (m, K
) (3). (1) gives the radiation spectrum. By integrating this with respect to λ, it is possible to obtain the radiant energy W emitted from the blackbody surface per unit area per unit time.

W-βT' (4) This is called the Stefan-Polzmann law β=, 5.55X10-
56rg-61n-'', S'·K-' (5).

Usually, temperature is measured by measuring the total energy of radiation as shown in equation (4).

The object to be measured is not actually a black body. The ratio of the radiant energy of a black body at the same temperature to that of an object is called emissivity. This is a constant between 0 and 1.

The amount appearing in the output of the detector is the product of the spectrum of the blackbody width pair in equation (1), the emissivity of the object, the transmittance of light for each wavelength in the path, and the sensitivity characteristics of the detector depending on the wavelength. It is the integral of . These functions are complex and not necessarily known.

However, if the object to be measured is fixed and the radiation path detector is fixed, there is a one-to-one relationship between the temperature of the object and the output of the detector, and the output of the detector determines the temperature of the object. can be calculated. In many cases, there is a nearly linear relationship between the logarithm of radiant energy and temperature.

(B) Background technology From the queen's radiation amount, we can determine the temperature T ('K) of an object and the wavelength λ at which the radiant energy density radiated by the object is maximum.
m is 2m T = 2898μm −K (6
).

In the case of radiation temperature measurement of a high temperature object of 200° C. to 2000° C., the radiant light is mainly visible light and near-infrared light.

Considering the relationship in equation (4), the radiation thermometer is suitable for high temperature measurement.

A radiation thermometer consists of a condensing optical system that condenses the light emitted from the object to be measured, a detector that detects the intensity of the light, an amplifier that amplifies the electrical signal generated by this, and an amplifier that amplifies the electrical signal. It consists of a linearizer that determines the temperature from the temperature, and a recorder or indicator.

This is the basic structure, but the object to be measured and the detector must be close to each other, which is inconvenient as it is.

Therefore, a device is used that uses a red fiber to transmit the radiation light from the object to be measured to the detector.

FIG. 3 is a side view of a known configuration of a radiation thermometer using an optical fiber.

The light emitted from the object to be measured 3 is condensed by the condensing optical system 2 and enters the front end of the optical fiber 1 in a concentrated manner. Optical fiber 1 is a silica glass fiber. The radiant light is transmitted through the optical fiber 1, enters the data processing device 4, and is converted into temperature.

The data processing device 4 is a device in which a detector, an amplifier, and a linearizer are provided in one case.

The value obtained as the temperature is recorded on the recorder 5.

Optical fibers are useful for measuring the temperature of certain parts of objects in complex locations or intricate shapes.

In the case of relatively high-temperature objects, the radiant energy is strong and the radiation mainly consists of visible light to near-infrared light, so it can be transmitted using a silica glass fiber. There is also less disturbance radiation emitted into the fiber.

However, in order to measure the temperature of a low-temperature object of 0 to 200 DEG C., the radiation thermometer configured as shown in FIG. 3 is insufficient.

(I) Disadvantages of the Prior Art In such a temperature range, far-infrared light with a wavelength of 8 to 12 μm occupies most of the spectrum of the emitted light. Since silica glass fiber cannot be used due to its large attenuation, an infrared fiber must be used. It is also necessary to use an infrared detector.

When targeting a low-temperature object, in addition to the change in wavelength becoming longer, the radiation intensity itself becomes weaker and the signal component decreases, as shown in equations (1) and (4), so the noise level changes. As the distance increases, it becomes important to eliminate noise.

When an infrared light transmission fiber is used, since this is a finite temperature, a black body width pair is generated depending on this temperature. Such infrared light is called disturbance. This results in noise. Since the signal component and noise level are approximately the same, the correct temperature of the object to be measured cannot be determined unless the noise is removed.

The sum of the signal component and the disturbance component appears in the output of the infrared detector.

Temperature correction is the process of removing disturbance components from the detector output, extracting signal components, and determining the correct temperature.

Japanese Patent Application Laid-Open No. 58-196430 (published on November 15, 1982) describes a radiation system in which two identical fibers are installed close to each other in parallel to detect the strength of disturbance components and calculate signal components. A thermometer is suggested.

Bundle infrared light transmission fibers with the same characteristics.

Radiant light emitted from the object to be measured is focused and made incident on one of the fibers. The other fiber has a blind plug at its front end to prevent light from entering from the front end surface.

An infrared detector is provided at the rear end of each of the two fibers.

Those with blind plugs only have disturbance components. This is estimated to be equal to the magnitude of the disturbance component in the other fiber.

Let us assume that the energy when it is transmitted through the infrared light transmission fiber and enters the detector is 11, I2. The signal component of 11 is assumed to be 5 (To). The disturbance component is written as R(TI). T, fd is the average temperature of the first fiber, and the strength of the disturbance is determined by the average temperature. To is the temperature of the object to be measured, which is the target quantity to be determined.

The disturbance component of the second fiber with a blind plug can be written as R(I2), where its average temperature is I2. Therefore, the input of each detector is L = S (To) +
R(TI) (7)I2 = R
(I2) ' (8)
becomes. To find 5(To) from these two quantities 11% 12, it is necessary to calculate T1-I2.

However, the structure of JP-A-1!158-196430 has the following drawbacks. Two infrared light transmission fibers are simply provided close to each other, and heat transfer between them is carried out through space. It's just radiation. In this case, even if there is a temperature difference between the two fibers, they will not easily reach the same temperature.

Since there is air between the two pieces of wood, heat is not easily transferred by air currents from the outside.

Air is considered to be unsuitable as an intermediate medium because of its high heat insulating properties.

Fibers are relatively cold. Object to be measured is 0 to 200
℃, the fiber will also be in this temperature range. Then, the radiation is weak and does not transfer enough heat between the two fibers.

It cannot always be said that TI ``'' T 2. Therefore, the disturbance R(Tl) added to the two-tree phino
It cannot be said that R(I2) are equal; it is not necessarily the case that (I
I-I2) does not provide a signal s (TO).

There are such drawbacks.

(1) Purpose The purpose of the present invention is to provide a radiation thermometer that can accurately measure the temperature of objects at relatively low temperatures of 0 to 200°C.

Two infrared light transmission fibers are used. One transmits signal components and disturbance components, and the other detects disturbance components.

This point is the same as the invention described above.

However, in the present invention, the structure is such that heat transfer between the two fibers is increased.

(E) Configuration The radiation thermometer of the present invention uses two fibers to detect disturbance components and perform temperature compensation.

Unlike the prior art described above, the two fibers are covered with an inner sheath made of a good thermal conductor and further covered with an outer sheath ring made of a heat insulating material. This is to facilitate heat transfer between the two fibers and to set TI=T2.

FIG. 1 shows a radiation thermometer of the present invention. FIG. 2 is a cross-sectional view of a portion of the fiber.

Among the infrared light transmission fibers, one that transmits signal light is called a signal fiber 6, and one that detects disturbance light is called a disturbance fiber 9.

At the end of each fiber 6.9 there is an infrared detector 7.1.
1 is provided.

The infrared light emitted from the object to be measured 3 is incident on the front end of the signal fiber 6 by the condensing optical system 2, and then
It is transmitted through the.

The synchrotron radiation generated within the signal fiber 6 itself also enters the infrared detector 7, so as shown in equation (7), ■+ =
s (To) + R ('r+) (9
).

The front end of the disturbance fiber 9 is closed by a fixture 8. The material for the fixing jig 8 is desirably one having an emissivity of 0.05 or less. As for the material, we use non-metallic materials such as quartz glass and alumina, which are heat insulating materials.If necessary, we use zinc, which is a low emissivity material, for the inner surface (zinc, which has an emissivity of 0).
．． 05), tin (emissivity 0.043, lead (0.05
) is preferable.

The signal fiber 6 and the disturbance fiber 9 are integrated by an inner sheath 13 having good thermal conductivity.

On the outside of the inner sheath 13, on the contrary, an outer sheath ring 14 made of plastic or the like and having excellent heat insulation properties is provided.

The inner coating 13 is a coating that tightly wraps the two fibers and makes their average temperatures T1 and T2 equal. This waste is used as a thermally conductive coating.

A metal coating is suitable for this. It is also possible to make a metal cylinder with a suitable inner diameter in advance and insert the two fibers into it. In order not to impair flexibility, the metal must be thin and the two fibers must be movable relative to each other within the inner sheath 13.

Therefore, the metal coating may be a bellows-shaped cylinder instead of a straight cylinder.

Instead of a cylinder, gold tape may be wound around the outer periphery of the two fibers.

The outer covering ring 14 is a heat-insulating covering. This can be done by extruding a material such as plastic, or by coating a resin by baking.

It is also possible to wrap a tape or the like containing glass fiber or the like to form the outer ring 14 with good heat insulation properties.

Although not shown, an outermost layer may be applied to the outer side of the outer sheath ring 14 to have the same structure as the outer sheath of an electric wire or an optical fiber. In this case, a thick coating of soft vinyl chloride resin is used.

The jacket ring 14 suppresses heat exchange between the two fibers and the external environment, thereby minimizing the influence of the external environment.

Due to the structure in which the two infrared light transmission fibers 6.9 are covered with the inner jacket 13 and the outer jacket ring 14, the two fibers 6.9 are hardly affected by external disturbances, but are affected by external disturbances. Even in this case, the two fibers are under the same thermal conditions and the temperature is kept the same. As a result, correct temperature compensation information can be obtained by the disturbance fiber 9.

Selecting a material with low emissivity for the fixing jig 8 is as follows:
This is to reduce the amount of infrared light that enters the end face of the disturbance fiber 9 from the fixture 8. Disturbance component R of disturbance fiber
(T2) and the input input from the disturbance fiber to the detector■
2 is equal to one limit, as shown in equation (8), and there is something incident on the end face from the fixing jig 8. When the temperature of the fixture is Ts, and the emissivity is ε, the component incident on the end face from the fixture 8 can be written as εQ ('r8).

l2=R(T2) 1εQ(Ts) 00
It is desirable that the second term in Equation 00 is 0. Therefore,
For the fixing jig 8, a material with low emissivity is selected.

The outputs of the signal detector 7 and disturbance detector 11 are input to a data processing device 12 . The data processing device 12 includes an amplifier,
Linearizers etc. In addition to this, a differential amplifier or the like may be provided to amplify the difference between I7.12.

The differential amplifier calculates (II-I2). this is,(
9), On to ε-00 limit, equal to s('ro). T.

Since the relationship between and S is known in advance, the temperature To of the object to be measured can be determined by linear live.

The temperature To is recorded on the recorder 5. Furthermore, a digital or analog display may be provided on the display.

As an infrared light transmission fiber, (1) Kurirum halide TgBr, KH2-5 (2) Alkali halide C8Br, C3l (3) Silver halide Ag　Br,　Ag　CA’ etc.

(Force) Effect (1) JP-A-58-1964 using two optical fibers
Unlike the invention of No. 30, the transfer of heat is not only by radiation, but rather by conduction. Because it is a relatively low-temperature object, radiation is small, and heat conduction is greater. Therefore, the average temperature of the two fibers becomes more uniform. T
It is likely to be held at 1=72. This is because the two fibers are surrounded by an inner jacket made of a good thermal conductor.

(2) Since the two fibers are wrapped in an outer jacket with excellent heat insulation properties, it is less affected by the external thermal environment.

It is difficult to get out of the T+-I2 state.

(3) Since it uses an optical fiber, it can be used to measure the temperature of objects with complex shapes or objects in crowded places.

(4) It can be used to measure the radiation temperature of objects at low temperatures of 0 to 200°C.

(5) Not affected by electromagnetic noise.

(6) Local temperature measurements can be made.

(7) Faster response speed than contact temperature measurement using thermocouples.

(g) Example Two infrared light transmission fibers each having a diameter of 1.
0 questions, a KH2-5 fiber with a length of 1 m was used. A fixing jig 8 made of quartz glass was provided at the tip of the disturbance fiber for disturbance evaluation. The two fibers are wrapped with metal tape.
Integrated by plastic coating.

A Zn5e lens was used as a condensing optical system.

A HgCdT6 detector was used as an infrared detector.

The following experiment was conducted using the radiation thermometer as described above.

A heating wire covered with plastic was used as the object to be measured. When heated between 0 and 200 degrees Celsius by applying electricity,
The temperature was measured using the following three methods.

(1) Measurement with thermocouple.

(2) Radiation temperature measurement according to the present invention.

(3) Although it is a radiation temperature measurement, the fiber is a single tree and no temperature correction is performed.

Regarding (2) and (3), in order to evaluate the influence of disturbance, the 10σ part in the middle of the infrared light transmission fiber was
It was heated to 00°C and an abnormal disturbance was forcibly applied.

The method using a thermocouple and the method of the present invention agreed within the range of error when the temperature of the object to be measured was between 0 and 200°C.

A temperature difference of 10 to 20% was observed between the thermocouple method and radiation temperature measurement without temperature correction.

It can be seen that the radiation temperature measurement device of the present invention can appropriately correct the influence of disturbance and accurately measure the temperature of a low-temperature object.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of a radiation thermometer of the present invention. FIG. 2 is a sectional view of the fiber portion in FIG. 1. FIG. 3 is a configuration diagram showing an example of a conventional radiation thermometer. 2... Condensing optical system 3... Measured object 5... Recording Total 6... Signal fiber 7... Signal Detector 8...Fixing jig 9...Disturbance fiber 11...Disturbance detector 12...Data processing device 13...Inner coating 14...Outer coating Inventor Ken Takahashi -Yoshi 1
) Noriyuki Patent applicant Sumitomo Electric Industries, Ltd. Samurai Kaiho 61-66131 (7)

Claims (3)

[Claims] (1) A condensing optical system 2 that condenses infrared light emitted from the object to be measured 3, a signal fiber 6 that transmits the condensed infrared light, and an infrared light transmitted through the signal fiber 6. A signal detector 7 that detects the intensity of external light and converts it into an electrical signal, a signal fiber 6, a disturbance fiber 9 provided parallel to the signal fiber 6, and a low emissivity fixing device attached to the front end of the disturbance fiber 9. A disturbance detector 1 that detects the intensity of the infrared light transmitted through the jig 8 and the disturbance fiber 9 and converts it into an electrical signal.
1, a data processing device 12 that amplifies the output of the signal detector 7 and the output of the disturbance detector 11, subtracts the latter value from the former, and calculates the temperature of the object to be measured 3 from this value, and a signal fiber 6. A radiation thermometer comprising: an inner sheath 13 made of a material with good thermal conductivity and covering the disturbance fiber 9; and an outer sheath 14 made of a heat insulating material covering the outside of the inner sheath 13. (2) The radiation thermometer according to claim (1), wherein the fixing jig 8 is made of quartz glass or alumina. (3) A radiation thermometer according to claim (2), which uses a fixing jig 8 whose inner surface is coated with zinc, tin, lead, or the like.