JPS61288130A - Metal body temperature measuring device - Google Patents

Abstract

PURPOSE:To measure the real temperature of a metallic plate accurately without contacting by arranging a reflector opposite the metallic body at an interval and thus constituting a resonator, and measuring the reflection factor and brightness temperature of the resonator. CONSTITUTION:The resonator 10 consists basically of a cavity part 11, a reflecting flange part 13, and a rear end wall 14. The cavity part 11 has an opening 15 facing the surface 1a of the metallic body 1, a flange part 13 is provided at the periphery of the opening 15 integrally with the cavity part 11, and many rod type projections 12, 12... are projected regularly from the surface facing the surface 1a of the flange part 13. On the other hand, the rear end wall 14 which has a resonance window 16 which communicates with the inside and outside of the cavity part 11 is provided at the rear end of the cavity part 11 and the storage chamber 17 for an antenna element 4 which include the rear end wall 14 as its front wall communicates with the cavity part 11 through the resonance window 16 behind the cavity part 11. Then, the reflection factor and brightness temperature of the resonator 10 in the specific frequency band having the center frequency as high as the resonance frequency of the resonator 10 are measured to find the real temperature of the metallic body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for measuring the temperature of a high-temperature metal body such as a heated steel plate in a continuous annealing furnace or the like in a non-contact manner.

[Prior Art] Conventionally, methods for measuring the temperature of a high-temperature metal body using a non-contact method include a radiation thermometer and an optical pyrometer, which measure the surface temperature of a metal body by measuring the thermal radiation energy of the metal body. There was a way to use etc. However, with these methods, it is not possible to accurately measure temperature if the emissivity of the metal object being measured fluctuates, so using a method that uses reference radiation,
The method used was to simultaneously measure emissivity and determine temperature.

On the other hand, the present inventors have developed a method to measure the emissivity at the same time to accurately determine the true temperature.

In #Kokai No. 58-102118 (hereinafter referred to as the prior invention), a resonator is formed by arranging a reflector facing a metal object to be measured, and a predetermined resonant frequency with the resonant frequency of this resonator as the center frequency is disclosed. We previously proposed a method to determine the true temperature of a metal body by measuring the reflectance and brightness temperature of the resonator in the frequency band. This prior invention is configured to measure the emissivity and brightness temperature in the microwave or millimeter wave band with a wavelength of 04 mm or more, but in general, the reflectance of a metal body in the microwave or millimeter wave band is extremely close to l, and the emissivity is is so small that it is difficult to accurately measure its emissivity. Therefore, in the prior invention, microwave,
In the millimeter wave band, it is possible to easily construct a resonator by providing a reflector facing the metal body, and near the resonant frequency, the reflectance decreases due to the resonance phenomenon (the emissivity can be increased). ) using
A configuration is disclosed in which the true temperature is accurately determined from the measured values of reflectance and brightness temperature.

[Problems to be Solved by the Invention] In the above-mentioned prior invention, the loss (leakage) due to diffraction between the metal body and the reflector arranged opposite to it and forming the resonator is not so small that it can be ignored. Therefore, it is not possible to accurately determine the true temperature of the target metal body from the reflectance and brightness temperature of the resonator, and if the position of the target metal body changes and the amount of leakage changes, the true temperature measurement will be significantly affected. affect.

Therefore, the present invention solves this problem and provides a method for accurately measuring the true temperature of a metal plate without contact using a resonator with a structure that can minimize loss (leakage) due to diffraction. It is intended to.

[Means for Solving the Problems] The present invention for solving the above-mentioned problems comprises constructing a resonator by arranging a reflector at a distance so as to face a metal body to be measured, and reducing the resonance of this resonator. An apparatus used in a method for determining the true temperature of a metal body by measuring the reflectance and brightness temperature of an i-resonator in a predetermined frequency band with the center frequency being the center frequency; a reflective flange portion provided around the opening of the cavity portion and having a plurality of protrusions facing the surface of the metal body and protruding toward the surface thereof; and a reflective flange portion that connects the inside and outside of the cavity portion. A rear end wall having a communicating resonant window is used as a component of a resonator.

[Function] In the present invention, the reflector is formed by a flange having a plurality of protrusions.

Therefore, due to the presence of the protrusion, loss (leakage) due to diffraction between the metal body and the reflective plate as in the prior invention.
Thereby, the true temperature can be measured accurately. This point will also be clarified by the examples described later.

[Specific examples of the invention] The present invention will be explained in more detail below.

First, prior to a detailed explanation of the present invention, a method for measuring the temperature of a metal body according to the prior invention will be explained with reference to FIG. l is the metal object to be measured.

Reference numeral 1a indicates a surface portion thereof, and reference numeral 2 indicates a metal reflection plate of an arbitrary shape such as a copper concave mirror, which is arranged opposite to the metal body surface 1a and forms a resonator 3 with the metal body 1. here,
The resonator 3 refers to a system in which radio waves of a certain frequency resonate within the space between the reflector 2 and the metal surface 1a, and 4 is an antenna element disposed approximately in the center of the reflector 2. 5 is a coaxial line connected to the antenna element 4.

Coaxial! The other end of i5 is connected to a common terminal of the changeover switch 6. One terminal 62 of the changeover switch 6 is
As shown in FIG. 7, it is connected to a resonator reflectance measuring device 7 that measures the average reflectance ρ of the resonator 3 in a constant frequency bandwidth B with the resonant frequency fO of the resonator 3 as the center frequency, and a changeover switch 6 The other terminal 63 of is connected to a high-sensitivity receiver (radiometer) 8 that measures the brightness temperature TA of the resonator 3.
It is connected to the. The output of the radiometer 8 and the output of the reflectance measuring device 7 are input to a temperature calculation circuit 9, and an output corresponding to the temperature of the metal body 1 is obtained.

Let P be the average reflectance of a constant bandwidth B with the resonant frequency fo of the resonator as the center frequency, and let the average emissivity be the average emissivity.

The brightness temperature of the bandwidth B of the resonator is TA, the average emissivity in the bandwidth B of the reflector and metal body that make up the resonator is ε, respectively, and εt1 is the temperature of the reflector and the metal body Tm, Tt,
Then, from the relationships of the following equations (1) to (3), the temperature Tt of the metal body is finally expressed by equation (4). Note that equations (2) to (4) hold true when the loss of the resonator due to diffraction is negligibly small.

ey l-P -=-(1'12=
E' Taiju and ----- (2) TA = Mo □ 1 + No - τ ----- (3) Here, the temperature of the reflector T
m is actually measured using a thermocouple or the like. However, in reality, it is kept at a constant temperature by water cooling. ε/εt can be set so that 8/2t<t by changing the material and shape of the reflector, or can be set in advance so that 8/2t<t.
Measure the value (ratio) of

The temperature calculation circuit 9 calculates the brightness temperature T of the resonator according to equation (4).
The temperature Tt of the target metal plate is determined from A and the average reflectance e. The average reflectance e is measured as follows. That is, when the switches 61 and 62 are connected, the microwave (or millimeter wave oscillator 71)
A microwave (or millimeter wave) with a constant bandwidth centered around the resonant frequency fO is applied to the resonator 3 through the waveguide 75, and the reflected wave from the resonator 3 is detected through the directional coupler 72. The average value ■2 of the detected output output from the detector 73 is measured by a signal processing circuit 74 such as an integrator. When 61 to 63 of the switch 6 are connected, the By short-circuiting the waveguide 75 at the 1,76 point, a state of reflectance = 1 (P = 1) is formed, and the 0 reflectance measurement circuit 77 that measures the detection output V1 at that time, calculates this V, . Average reflectance p (=Vz/Vt) is calculated from vz.

The brightness temperature TA is measured by the radiometer 8 when the switches 61 to 63 are connected. A radiometer is a minute noise power measurement device in the microwave or millimeter wave band. In the microwave or millimeter wave band with a wavelength of 0.4 mm or more, the noise power P emitted from an object with a brightness temperature TA is calculated by the following formula % Formula % where k is Portzmann's constant and B is the measurement frequency bandwidth of the radiometer.

The configuration shown in FIG. 6 shows a Dicki-biased radiometer, in which the noise power radiated from the resonator and the noise power of a predetermined magnitude output from the comparison noise power generator 82 (83 is an attenuator ) are switched by a switch 81 at a constant frequency based on a synchronous oscillator 88. The noise power that has passed through switch 81 is amplified by amplifier 84 and local oscillator 91 . The frequency of the signal is converted by a mixer 85 and detected by a detector 86 . A synchronous detector 87 synchronously detects the signal output from the detector 86, and is controlled by the synchronous oscillator 88. 89 is an integrator that integrates the output signal of the synchronous detector 87, and 90 is a brightness temperature calculation circuit that calculates the brightness temperature TA of the resonator 3 based on the signal output from the integrator 89.

By the way, when the loss due to diffraction of the resonator is small enough to be ignored, the above formulas (1) to (4) hold true.
On the other hand, is there a loss due to diffraction? is not negligible, equations (1) to (4) become ε=l P
−−−CQε= et+shi+已 −(
7) −n=Et Tt + 100; −+22i−−−−(
8) (Here, 800 indicates thermal radiation that enters the resonator from outside the resonator and affects the measurement.) If the range is large, always P and T) <If not known, the average reflection If the true temperature Tt cannot be determined accurately from the rate e and the brightness temperature TA, and if the position of the target metal body changes and the amount of loss (281) changes, 2.
TX fluctuates, greatly affecting true temperature measurement.

Therefore, in the present invention, the resonator 10 is constructed as follows, in contrast to the resonator 3 of the prior invention, in order to reliably prevent leakage.

That is, the resonator 10 has, as shown in FIG. t51A to FIG. 2, an empty Iri portion 11, a reflective flange portion 13 having a protrusion 12, and a rear end wall 14 as basic components.

The cross section of the cavity 11 is rectangular or circular as shown in the figure. The cavity 11 has an opening 15 facing the surface 1a of the metal body 1, and a rectangular (illustrated example) or circular reflective flange 13 is provided around the opening 15.
1, and furthermore, a large number of rod-shaped projections 12.about.12 are regularly provided protruding from the surface opposite to the surface 1a of the reflective flange portion 13.

On the other hand, at the rear end of the cavity 11, there is a rear end wall 1 having a circular (illustrated example) or rectangular resonance window 16 that communicates the inside and outside of the cavity.
4 are provided. Roughly at the rear of the cavity 11, a storage chamber 17 for the antenna element 4 is provided with the rear end wall 14 as a front wall, and communicates with the inside of the cavity 11 via a resonance window 16.

Here, the shape of the protrusion 12 may be a square bar as in the above example, or a circular line, but its cross-sectional dimensions, length, and interval between protrusions are preferably determined as follows.

(a) Due to the resonant frequency fO of the resonator, π/2 in β standing 1
Determine fLl so that Here β=2π/in o
=2πfo/c (input 0: resonance wavelength, c=3X10
Layer/S).

(b) For the distance d between the target metal body and the resonator, lx
2 is also determined so that lx≧d.

(C) Determine fLz when βΦ becomes π2 out of 3.

In this way, the spacing between the bar-like protrusions is determined by the frequency used. Therefore, the density of protrusions is determined by the frequency. As for the number of protrusions, increasing the number of stages (columns) is more effective in reducing loss.

It should be noted that conical or anti-spherical protrusions are difficult to manufacture and are less effective in preventing leakage.

On the other hand, the cross section (aXb) and length L of the cavity 11 are determined by the resonance frequency fo used for measurement. The resonance window 16 may have any suitable shape such as a circular window, a rectangular hole, a slit hole, etc. The size of this window is determined by the size of the waveguide that transmits the microwave (or millimeter wave) to which the cavity 11 connects at the time of resonance. Generally, it is selected to match the tube section (in this case, the 17 antenna element storage chamber section), but it is selected under the condition that the reflectance of the resonator is the smallest for the frequency band measured by the radiometer. It is preferable to do so.

The size of the window is determined to obtain a resonance peak suitable for temperature measurement with respect to the cavity size. The resonant frequency in the case of temperature measurement is determined by the size of the resonator. Therefore, when the plate vibrates, it changes. In that case, a voltage control filter is inserted into the radiometer to detect changes in the resonant frequency, and the reception band of the radiometer is controlled by the voltage control filter so that the brightness temperature at the resonant frequency is always measured.

Note that it is desirable that the flange portion 13 and the cavity portion have a double-wall water-cooled structure so as not to be affected by heat from the metal body.

Further, in the present invention, the flange portion may have a concave mirror shape similar to the conventional example.Furthermore, a surrounding plate 18 is provided around the outer periphery of the flange portion 13, and the protrusion 12.
It is effective to prevent leakage from between the two.

[Example] Next, examples will be shown.

An example will be shown in which the temperature of a metal plate was measured without contact using the resonator structure of the present invention.

The resonator structure of the present invention had the following shape and dimensions.

■Flange part with protrusions/protrusion shape diagonal column φ Number of protrusions = 50/Dimensions: ! ; Lx = 44 layers, 1z = 24 layers.

View 1 = 40m layer・Distance between resonator and target metal plate j@: d=20mm・Flange size: 328m×284×Resonance window・Window shape: Circular hole・Window frame: 53 layers φ・Thickness :3I1ml ・Window position: Hole in the center of the cavity cross section ■Cavity section ・Cross-sectional dimensions: A128mm x b64mm L90
Baking soda, resonance frequency: 1.7 GHz A radiometer with the following specifications was used.

Center frequency: 1.7 GHz Medium frequency range: 20 MHz Power amplification factor: 80 dB Dicki modulation: 1 kHz Figure 4 shows a metal plate (steel plate) using the resonator structure of the present invention.
The results of measuring the temperature are shown.

The loss P due to diffraction is minute (0,001xF, or less), and from the reflectance P and brightness temperature TA of the resonator, (1) ~
It was possible to accurately measure the temperature of the object using the relationship in equation (4) (accuracy within ±8).

On the other hand, when the resonator is configured with a cavity having a flat flange as shown in Fig. 3, the loss due to diffraction and 8 ('2'' + 0.87) are measured at a distance of 20 am. Therefore, it was not possible to accurately measure the temperature of the object using the relationships of equations (1) to (4) (Fig. 5).

[Effects of the Invention] As described above, according to the present invention, since the protrusion is provided on the flange portion, loss (leakage) can be reliably prevented and the true temperature can be determined accurately.

[Brief explanation of drawings]

FIG. 1A is a longitudinal sectional view of a resonator according to the present invention, FIG. 1B is a front view of the resonator, FIG. 2 is a schematic perspective view, and FIG. 3 is a longitudinal sectional view showing a comparative example of the resonator. 4 and 5 show phase 58 temperature measurement accuracy by the device of the present invention and the comparative example device.
6 is a block diagram of the prior invention, and FIG. 7 is an explanatory diagram of the reflectance of the resonator. 1°00. Metal body 7, reflectance measuring device 8
,,,,Radiometer 10. , , resonator 11
, , , cavity 12. ,,Protrusion 13 ,,,
, flange portion 14. , , Resonance window Fig. 1A Fig. 1B Fig. 2 Fig. 5 Gold side body temperature L (K)

Claims (1)

[Claims] (1) A resonator is constructed by arranging a reflector at a distance to face the metal object to be measured, and the reflectance and brightness of the resonator in a predetermined frequency band with the resonant frequency of the resonator as the center frequency. An apparatus used in a method for determining the true temperature of a metal body by measuring temperature, comprising: a cavity opening facing the surface of the metal body; and a cavity provided around the opening of the cavity, A reflective flange portion having a plurality of protrusions facing the body surface and protruding toward the surface side, and a rear end wall having a resonant window communicating the inside and outside of the cavity portion are used as constituent elements of the resonator. A metal body temperature measuring device featuring: