JPS59226835A - Radiation thermometer - Google Patents

Abstract

PURPOSE:To reduce an error in a measured temperature even if the emissivity of a body to be measured varies by finding the presence range of a real temperature from the transmission wavelength of an in-use filter and set emissivity, and regarding the mean value of the upper and lower limit values of the range as the measured temperature. CONSTITUTION:The output signal of a detector 31 is sent to a signal separating means 52 through an amplifier 51. The signal separating means 52 finds the spectral radiation brightness values L1 and L2 of light transmitted through a filter 211 and light transmitted through a filter 212, and outputs separately the signals corresponding to L1 and L2. An operation means 60 receives said signals corresponding to L1 and L2 from the signal separating means 52 and calculates the measured temperature of the body to be measured on specific operation basis. Namely, the presence range of the real temperature is found from the transmission wavelengths lambda1 and lambda2 of the filters in use and the set emissivity values lambda1 and lambda2, and the upper-limit value and lower-limit values of the range is regarded as the measured temperature. Thus, an error in the measured temperature is reduced even if the emissivity of the measured body varies.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention allows light emitted from an object to be measured to pass through a plurality of types of filters having different wavelengths (wavelength C or less at which the transmittance reaches a maximum value, defined as a transmission wavelength). This relates to a radiation thermometer that determines the temperature of an object to be measured based on transmitted light.

Radiation thermometers have the advantage of being able to measure the temperature of an object to be measured without contact, and are therefore used to measure the temperature of heated steel.

First, the principle of such a radiation thermometer will be explained.

The spectral radiance Lλ,T emitted by the object is the temperature T of the object.
Transmission wavelength λ of a filter through which the emitted light from one object is transmitted
and the emissivity ε of the object, which is given by the following formula using Wien's formula and Blank's formula.

Here, C1:1.19096XjO[W-m]C2:
0.014388 [m-K] The transmission wavelength of the filter through which the emitted light from the object is transmitted is λ1. λ2, transmission wavelength λl, emissivity of the object at λ2 is 6. , ε2, the spectral radiance Ll, L2 at each transmission wavelength λl, λ2 and emissivity a++'2 becomes C. Dividing equation (2) by equation (3) gives the following equation, and calculating the temperature T from this equation gives the following equation. This formula is a formula for determining the temperature by measuring the spectral radiance 14 + L2.

In general, it is difficult to determine the emissivity 81□ε2 because it changes not only depending on the wavelength and temperature but also depending on the surface oxides, deposits, etc. of the object.

From this, the emissivity εI+'2 is the transmission wavelength λ1. λ2
Assume that ε is 82 without changing. K like this
Then, equation (5) becomes as follows.

The principle formula for a two-color thermometer that measures temperature using light of two different wavelengths is (6)2.

Next, an example of a conventional configuration of a radiation thermometer to which such a principle is applied is shown in FIG. Here, in the radiation thermometer,
The case of a two-color thermometer is shown.

In FIG. 1, 10 is a light focusing section, 20 is a filter wheel, 30 is a detection section, and 40 is a calculation section.

In the light focusing section 10, the light emitted from the object to be measured is focused by the objective lens 11.

Filters 211 and 212 with different transmission wavelengths of 2 and λ2 are attached to the filter wheel 20 and rotated by a motor 22. Depending on the rotational position of the filter wheel 20, the light focused by the objective lens 11 is transmitted through filters 211 and 212.

In the detection unit 30, 31 is a detector, and the filter 2
Detects the light that has passed through 1, converts it into an electrical signal, and outputs it. 52 is an automatic gain amplifier (hereinafter referred to as AGc amplifier)
The detector amplifies the electrical signal from the moon. A signal separator 33 separates a signal corresponding to the light transmitted through the filter 211 and a signal corresponding to the light transmitted through the filter 212 into electrical signals v1 and v2.

These electric signals vl and v2 are sent to the calculation section 4o.

Reference numeral 34 denotes a synchronizing signal generator, which is arranged close to the filter wheel 2° and transmits light through the filters 21. , H2 is sent to the signal separator 35.

In the calculation unit 40, the electric signal v1 is zero clamped 41
sent to. Further, the electric signal (2) is sent to a zero clamp 41 and a comparison amplifier 42. The zero clamp 41 outputs a signal when a signal corresponding to a temperature above a certain temperature is sent. The output signal of the zero clamp 41 is sent to the amplifier 4
3 and becomes the output signal of the thermometer. Comparison amplifier 4
2 is given the electrical signal V2 and the output vo of the reference voltage source 44. Then, the output of the comparison amplifier 42 is the AGC
is applied to the amplifier 52, which causes the electric signal V to be
The gain of the AGC amplifier 42 is adjusted so that 1 becomes a constant value vo.

The electrical signals V, V2 of such a radiation thermometer are given by the following equations.

Vl=L(λl+T) RvlG IJt
(7) v2=L(λ21 T ) Rv
2 G +'2 (8) Dividing equation (7) by equation (8), If the output signal of the thermometer is vx, vx is the electric signal v1
Since it is proportional to V, :KVl (tl, where K is a constant.Also, since the electric signal v2 is controlled to the output vo of the reference voltage source 44 so that it always has a constant value, , vo-Kv2, and from this equation we get ■0all ■2.Substituting equation 01 into equation 01 gives us, and substituting equation (9) into this equation gives us. In formula 02, R,...
/Rv2*Ll+ /IJ2 and vO are values specific to the thermometer and can be considered constants. Also, L(λ,
, T)/L(λ2.T) corresponds to equation (4).

If output signal ■8 is obtained on such a radiation temperature side,
Ll/L2 in equation (4) is obtained. However, the emissivity ε! , ε2 are difficult to obtain. For this reason,
Assuming that the emissivities 61 and 62 are equal, the measured temperature of the object to be measured is determined using equation (6) in which εl and 62 are eliminated.

The calculation for determining the measured temperature will be explained below.

As the filters 211 and 212, the transmission wavelength is λ0.75 x 10= [m:], λ2 ==0.85
Using X To-' [m:], set the emissivity of the object to be measured to εl20, 7, ε2==0.8, and change the temperature of the object to be measured from 1000 [K] to 1600 [K]. ``It
As the temperature is changed, the error between the true temperature of the object to be measured and the temperature measured by the radiation thermometer becomes as shown in the graph of FIG.

In the graph of FIG. 2, the horizontal axis represents the true temperature T, and the vertical axis represents the error temperature and error rate. In the graph of FIG. 2, the solid line is the error temperature between the true temperature and the temperature measured by the radiation thermometer, and the broken line is the ratio of the error temperature to the true temperature (hereinafter referred to as error rate).

As is clear from the graph in Figure 2, the emissivity is 6° and 62°.
If there is a slight difference of 0.1 between the two, the temperature of the object to be measured will be 1600 (I(':)), and the error in the measured temperature will be about 140 [W] (error rate of about 9%).

For this reason, there has been a problem in that large errors occur in the measured temperature due to fluctuations in the emissivity of the object to be measured.

The present invention has been made in order to eliminate the above-mentioned problems, and it is an object of the present invention to provide a radiation thermometer in which the error in the measured temperature is small even if the emissivity of the object to be measured changes. purpose.

FIG. 3 is a diagram showing the configuration of an embodiment of the radiation thermometer according to the present invention, and here the case of a two-color thermometer is shown. In FIG. 3, the same parts as in FIG. 1 are given the same reference numerals.

In FIG. 3, 50 is a detection section, and 60 is a calculation means.

The output signal of the detector 31 is amplified by an amplifier 51 and sent to a signal separation means 52. The signal separation means 52 determines the spectral radiances Ll and L2 of the light transmitted through the filter 211 and the light transmitted through the filter 212, respectively, and separates and outputs signals according to these spectral radiances L1 and L2. . The synchronization signal generator 34 is connected to the filter wheel 20
A signal corresponding to the filters 217 and 212 disposed close to and used for transmitting light is sent to the signal separation means 52.

The calculation means 60 receives the spectral radiance L from the signal separation means 52.
1 and L2, and calculates the measured temperature of the object to be measured according to a predetermined calculation method.

In the radiation thermometer having such a configuration, the temperature of the DLL constant object is determined as follows.

With the radiation thermometer shown in Figure 3, the measurable temperature range is 100
0 to 1600 (K)], and the emissivity of the object to be measured is 0.
．． It is set in the range of 4 to 1.0. In addition, the detection unit 5
Based on the spectral characteristics of 0.0, the transmission wavelength of the filter 21 that can be used is 0.7 x 10 ~+, ox 1a [m
].

Based on these conditions, the filter to be used 211゜21
The transmission wavelength of 2 is λ1 == 0.75 x 10 [
rr+], λ220, 85×10 [m], and the spectral radiance is calculated from equation (1) and graphed when the emissivity is set to 1.0 and 0.4 at each transmission wavelength. If you do this, it will look like Figure 4.

In the graph of FIG. 4, the spectral radiance L is plotted on the vertical axis and the temperature T is plotted on the horizontal axis. Each transmission wavelength λ1. Curves a to d are determined by the combination of λ2 and emissivity of 1.0.4.

Now, for the light transmitted through the filter with wavelength λ1 = 0.75 x 10 [rnJ, the spectral radiance I4 =
7 x 10'[W/mr/m') is measured, and the wavelength λ
The spectral radiance L2-2×108 [W
/sr/m ] is measured. Two transmission wavelengths λ7. Emissivity ε1 of the object to be measured with respect to λ2. ε2
is unknown.

In the graph of Figure 4, the spectral radiance L□ and graph b
Let the temperature found from the intersection with TL□ be TL□.

Since the temperature Tt is the temperature obtained when the emissivity is 1 at the wavelength λ1, it provides a lower limit.

Let T be the temperature determined from the intersection of the spectral radiance L1 and the graph 27d. The temperature T is within the wavelength
Since ul is the temperature obtained when the emissivity is the lowest, 0.4, an upper limit is given.

Similarly, the temperature Tt2 determined from the intersection of the spectral radiance L2 and the graph C provides a lower limit. Further, the temperature T 2 determined from the intersection of the spectral radiance L2 and the graph a provides an upper limit.

2 Temperature range given by temperatures Tu1 and T4 and temperature TXI
Since the true temperature T exists in the common range of the temperature ranges given by 2 and Tt2, TL1≦T≦T112. That is, the range is as shown by the diagonal line in the graph.

Although the true temperature T is between TLl and Tu2 and cannot be determined, the average value of the upper and lower limits of the common range is output as the measured temperature.

In the case of the range shown in the figure, the measured temperature Tm is as follows.

In the graph of Figure 4, T4 = +21s[K'), T
Since u2 = 1285 [K'), TrIN#
You can get 1250 [K'1 power. At this time, the maximum error temperature is ±35'c.

This error temperature is /J compared to the temperature error of -85 [υ] at 1250 [K] in the graph of Figure 2.
It's 1 smaller.

The arithmetic operations for determining the measured temperature as described above are shown in a 70-chart as shown in FIG.

The calculations shown in the flowchart of FIG. 5 are performed by the calculation means 60.

A case in which such a radiation thermometer is used to measure the temperature of steel heated in air will be described.

A sufficient oxide film is formed on the surface of the steel material, and the emissivity is about 0.8.

For this reason, the measurement temperature range is 1000~+6o.
o[:ni:], the emissivity of the object to be measured is 0.7 to 0.9,
The wave-i of the filter to be used is λl == o, 7sx 1
Let a (m), λ2=o, asx +o [m].

Based on these conditions, for each case where the emissivity of the object to be measured is 0.7 and 0.9, the filter wavelength gold λ
I=Q, 75 x 1G [m), λ2 = o,
Spectral radiance [when asxlo [rr+]
4, I4 is calculated using equation (1) and graphed as shown in FIG.

In the graph of FIG. 6, the spectral radiance L is shown in the vertical direction 1h11, and the temperature T is shown in the horizontal direction 111+. Each wavelength λl.

By the combination of λ2 and emissivity of 0.9 and 0.7],
Curves from e to h are required.

When the true temperature is 1/,00 [K], the emissivity ε is −ez=0
．． 9, from the graph in Figure 6, the spectral radiance u -, Ll = 2, 80 x 109
(W/sr/m”], L2=6.14X109CN
~shi/sram”].

When a radiation thermometer measures the spectral radiance of the sun as described above, the common range of upper and lower limits of temperature determined in the same way as described above is +600 < T < 1.
It becomes 635. If the center of this range is the indicated temperature TM, then TM
21617.5 (K).At this time, the error temperature is L617.5-1600: 17.s[t:'3.

On the other hand, when the true temperature is 1600 [K], ε1=62=0.7
Then, using the graph in FIG. 6, the common range for the upper and lower limits of temperature is 1565 < T < 1600, and the indicated temperature is 7. := 1582.5 [K:)
becomes. At this time, the error temperature is 1582.5-1/, 00 nee 17.5 [υ]. Therefore, the error rate of the measured temperature is ±1.1 [%].

Similarly, using the graph in Figure 6, we can determine that the true temperature is +o
If oo[Kl, the error rate of d1 moisture stability is ±0.
It becomes 9 [%].

As shown in the graph in Figure 6, if the emissivity range is small (emissivity 0.7 to 0.9), the fourth
The error rate is smaller than the measured temperature calculated from the graph in the figure (emissivity 0.4 to 1.0).

According to the radiation thermometer having such a configuration, the transmission wavelength λ1 of the filter used is λ1. λ2 and the set emissivity εl.

The range in which the true temperature exists is determined from the odor, and the average value of the upper and lower limits of this range is taken as the measured temperature. From this,
Even if the emissivity of the object to be measured varies, it is possible to eliminate errors that occur in the measured temperature.

In the embodiment, the radiation thermometer is a two-color thermometer, but the radiation thermometer 1 may be a multicolor thermometer that uses light of a plurality of different wavelengths.

As explained above, according to the present invention, it is possible to provide a radiation thermometer with a small error in constant temperature even if the emissivity of the object to be measured changes.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a conventional configuration example of a radiation thermometer, Figure 2 is a graph showing the temperature characteristics of the radiation temperature "1" error in Figure 1, and Figure 3 is a radiation thermometer according to the present invention. A diagram showing the configuration of one embodiment, Figures 4 and 6 are graphs showing the relationship between the spectral radiance of synchrotron radiation and the gain, and Figure 5 is a graph showing the temperature measured by the radiation thermometer in Figure 3. It is a flowchart of calculation. H, 21, 212...filter, 60... calculation means.

Claims (2)

[Claims] (1) In a radiation thermometer that allows light emitted from an object to be measured to pass through a plurality of filters having different transmission wavelengths, and determines the temperature of the object to be measured based on the light that has passed through each filter, the object to be measured has the following steps: Set a predetermined emissivity range for the object,
For the light transmitted through each filter, find the range in which the temperature of the object to be measured exists from the predetermined calculation formula within the set emissivity range, take the common range of each temperature range, and set the upper limit of this common range to A radiation thermometer characterized by comprising a calculation means for determining the average value of the lower limit values as the measured temperature of an object to be measured. (2) The radiation thermometer according to claim 1, wherein Wien's formula and Blank's formula are used in the calculation formula.