JPS5940250B2 - How to measure temperature and emissivity simultaneously - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simultaneously measuring the temperature and emissivity of an object to be measured, such as a steel plate.

Radiation thermometers are suitable for measuring the temperature of cold-rolled or hot-rolled steel sheets because they can be measured without contact, but the biggest weaknesses of radiation thermometers are emissivity and backlight noise.

The latter backlight noise is a big problem, especially when measuring the temperature of objects inside the reactor, and the solution to this problem is shielding. There are several possible ways to do this, from simple shielding with a cover to the use of specular reflection. To solve the former problem of emissivity, dichroic thermometers and other methods have been considered, but the present inventor measures emissivity and temperature simultaneously, thereby making accurate radiation temperature measurement possible. developed a method. However, in this method, the parameter α of the calculation formula used to calculate the temperature and emissivity is a constant. For example, after setting the parameter α to suit each object to be measured, such as a cold-rolled steel plate or a hot-rolled steel plate, Use it for each line. However, in this case, if the target of use changes, it is necessary to reconfigure the settings, which is extremely troublesome. The present invention aims to improve these points, to enable automatic correction of the parameter α, and to enable the above-mentioned radiation thermometer for simultaneous measurement of temperature and emissivity to be used immediately anywhere.

Next, this will be explained in detail. First, the principle of the aforementioned temperature and emissivity simultaneous measurement method will be explained. As shown in FIG. 1a, a cavity 2 is placed at a distance above the temperature-measuring object 1, and a radiation thermometer 3 is placed above it. The cavity 2 is a cylindrical body whose inner surface is a highly reflective mirror surface and whose both ends are open. Further, as shown in FIG. 1B, cavity 4 is placed in place of cavity 2, with other conditions being the same. This cavity 4 is a bottomed cylindrical body with an open side facing the temperature measurement object 1 and a closed side facing the radiation thermometer 3. The inner surface is a highly reflective mirror surface, and the closed end surface has a radiant In line with the thermometer 3, a hole L5 is opened. Now, if the surface temperature of the object 1 is T and the emissivity is ε, then the energy E4 incident on the radiation thermometer 3 in the case of Figure 1a is only the radiation energy that directly reaches the radiation thermometer 3 from the object 1. Therefore, it is not affected by cavity 2. Therefore, the following formula holds true. E1=ε
・Eb(T)・・・・・・・・・・・・・・・(Here, Ebm is the radiant energy of a black body at temperature T.

On the other hand, in FIG. 1B, the radiation from the object 1 is reflected multiple times in the cavity as shown, and a portion of the multiple reflected emissivity also enters the radiation thermometer 3 through the small hole 5. Therefore, the incident energy E2 becomes large, and the apparent emissivity ε of the object 1 increases.
has increased. This increased emissivity is expressed as g(ε)
Then, the following formula holds true. E2=g(ε)・Eb(T
) ・・・・・・・・・・・・・・・(2) If the functional form of emissivity g(ε) is known, ε, T can be obtained from equations (1) and (2).
It is possible to obtain

This is the emissivity g(ε), but in order to find this functional form, the following assumptions are made: (1) The temperature of the cavity surface is sufficiently low compared to the surface temperature of the object 1, and the Radiant energy is negligible. (4) The effective reflectance γa at the lower end opening surface of the cavity is uniquely determined by the shape and dimensions of the cavity, and the reflectance of the inner surface.
0Ii) The energy re-radiated from the cavity to the object surface is reflected back into the cavity at a ratio of (1-ε)·p.

p is a constant that does not depend on ε. Under the above assumptions,
The radiant energy E2 is calculated as follows. Therefore, it can be seen that the emissivity g(ε) is expressed as (α+1)·ε/(ε+α).

Here, α is a constant setting parameter expressed by the following formula. By setting the parameter α, E2/
Assuming that E1=G, the emissivity ε becomes, and if the emissivity ε is known, the blackbody radiant energy Eb(1) can be found from the equation below, which is a modification of the equation α1).

Once Eb(?1r) is determined, the temperature T can be easily determined using Planck's equation. As a device for performing such measurements, a rotating sector 6 is placed between the cavity 2 and the radiation thermometer 3 as shown in FIG. 2b, and this rotating sector is connected to a rotating shaft 7 as shown in FIG. 2a. It consists of two fan-shaped parts 6a and 6b arranged symmetrically with a central angle of 90 degrees,
Arc-shaped grooves 6c and 6d centered on the shaft 7 may be provided in the fan-shaped portion. In this way, the upper open end of the cavity 2 is alternately covered with the fan-shaped portions 6a and 6b of the sector 6 and the blank area between them, and is then left open, as shown in FIG.
, b can be obtained alternately. However, in this radiation thermometer, it is necessary to obtain the parameter α in advance from off-line experimental results, but this method lacks flexibility or quick response.

The present invention attempts to improve this point. As expressed by the above equation (5), the parameter α includes an unknown number p, etc., and a theoretical solution is difficult. However (5)
As is clear from the equations, the amount of radiant energy from the cavity to the object 1 reflected from the object to the cavity is determined, and the component a related to the cavity is a constant value determined by the cavity, and is variable. is the component p related to the object. Since the component p is related to reflection from the object to the cavity, it should be affected by the surface properties of the object. Therefore, the relationship between the surface roughness of the object and the parameters was determined, and the results are shown in Figures 3 and 3. As shown in Figure 4, a very good correlation was obtained. Here, FIG. 3 shows the roughness by the average inclination angle θa, and FIG. 4 shows the roughness by the root mean square roughness RMS. In addition, in Fig. 3, P1 is a stainless steel mirror surface, and P1 is a stainless steel mirror surface.
2 shows the measured values for an aluminum mirror surface, P3 a silicon steel plate, P4 a cold-rolled steel plate, and P5 a shotplast roughened aluminum plate.

Here, the average inclination angle θa means that when the surface of an object is uneven as shown in Fig. 5, the coordinate axis X,
If the coordinate axis Z is the thickness direction, the inclination angle is θ, and L is the desired range of consideration in the X direction, it is expressed as 1UU.

Further, the double mean roughness RMS is expressed by the following equation, where Zm is the center level of the surface of the wavy object. In addition to this, roughness display parameters include average roughness and Ra as specified by JIS.
There are various values such as maximum height R[Tlaxl, ten-point average roughness Rz, etc., but it is of course best to use one with a high degree of correlation.

Additionally, a stylus type is commonly used to measure Z, θ, etc.
It is possible to project a laser beam, measure the scattered light intensity distribution centered on the specular reflection direction, and determine the average tilt angle θa from the peak value and half-width of the distribution. FIG. 6 is an example of the relationship between the roughness average inclination angle θa and the half width H measured on the surface of a steel plate. Furthermore, a method of measuring the surface profile itself using an optical method as shown in FIG. 5 has recently been developed, and by using this method, it is possible to determine any roughness parameter without contact.

A roughness meter, especially an optical roughness meter capable of non-contact measurement, is attached to the radiation thermometer, and the radiation energies El and E2 are measured by the detection element of the radiation thermometer, and the roughness meter measures the radiation energies El and E2. Roughness Q
Find SUND or RMS, and from this figure 3 or 4
By determining the parameter α using the graph in the figure, emissivity ε using the parameter α and equation (6), and temperature T using equation (7), the surface temperature of any unknown object can be determined. Can be measured accurately. Of course, temperature measurement and roughness measurement may be performed at separate locations. As explained in detail above, according to the present invention, the surface temperature of a high-temperature object whose emissivity and surface texture are unknown can be measured extremely accurately using a radiation thermometer, and it can be used as a temperature measuring means in the iron industry and other fields. Extremely effective.

[Brief explanation of the drawing]

Figures 1A and b are schematic cross-sectional views explaining the principle of the simultaneous temperature and emissivity measurement method, Figures 2A and b are schematic plan views and side views showing specific examples of Figure 1, and Figures 3 and 3 are FIG. 4 is a graph showing an actual measurement example, FIG. 5 is an explanatory diagram of roughness, and FIG. 6 is an explanatory diagram showing the relationship between roughness average inclination angle θa and half width H. In the drawing, 1 is a temperature measured object, 2 and 4 are cavities, 3 is a radiation thermometer, and 6 is a rotating sector.

Claims (1)

[Claims] 1 A cavity with a high reflectance mirror surface on the inner surface is provided at intervals above the object to be measured, and the radiant energy E_1, E_2 from the object that simply passes through the cavity and that passes through the cavity with multiple reflections is measured. In the method of measuring the temperature and emissivity of the object, the surface roughness of the object is measured, and the temperature T is determined from the radiant energy based on the roughness.
and the calculation formula for emissivity ε=(α+1−αG)
/G and Eb(T)=E_1/s (here G=E_2
/E_1, Eb(T) is the radiant energy of a blackbody at temperature T)
1. A method for simultaneously measuring temperature and emissivity, characterized in that correct temperature and emissivity are determined by correcting parameter α.