JPS62153720A - Method and apparatus for measuring temperature using radiometer - Google Patents

Abstract

PURPOSE:To accurately measure temp. without receiving the effect of emissivity, by measuring the output of a radiometer in such a state that the magnitude of an antenna signal is made equal to that of a reference signal. CONSTITUTION:A reference antenna 31 is directed to a reference body 32 with emissivity of 1 and a noise signal Trec is outputted toward a circulator 33 from a signal processing part 36 through a second attenuator 34. The output signal of a radiometer 1 is directly inputted to the signal processing part 36 and further inputted to the signal processing part 36 through a lock-in amplifier 14. This signal processing part 36 controls the second attenuator 34 on the basis of the signal directly inputted from the radiometer 1 and calculates the temp. T0 of an object to be measured 20 on the basis of the signal inputted from the lock-in amplifier 14.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a temperature measurement method and a temperature measurement device using a radiometer. [Prior Art] Methods for measuring the temperature of an object can be roughly divided into contact It is divided into type and non-contact type. Contact measurement methods include methods that use thermocouples, resistance temperature detectors, etc., and although they have excellent measurement accuracy, they have the problem that they are not suitable for continuous temperature measurement or online temperature measurement.

On the other hand, a method using a radiometer is widely known as a non-contact measurement method, and is suitable for online temperature measurement such as measuring the temperature of a moving steel plate. There is a problem in that accurate measurement results cannot be obtained if the value fluctuates or is unknown.

For example, the conventional device shown in FIG. 4 will be explained.

In Figure 4, the radiometer (1) is a so-called day:
It is a radiometer called a type N.

Inside, from the input side to the output side, there are a first RF amplifier (2), a filter (3), and a second RF amplifier (4).
, a square law detector (5), and a video amplifier (6) are sequentially connected in series.

The input terminal of the radiometer (1) is connected to the output terminal (tOC) of the changeover switch αO. Changeover switch α
The first input terminal (IOA) of q is connected to the measurement antenna ui, and the second input terminal (l0B) is connected to the reference noise source (2).
is connected to the first and second input terminals (IOA
) and (IOB) are performed based on clock pulses generated by a clock pulse generator (to). This clock pulse generator (
6) applies the same clock pulse to the lock-in amplifier α, and the output signal from the radiometer (1) is input to the lock-in amplifier α.

Next, the measurement antenna αM is directed toward the measurement target,
The temperature measuring method of the conventional apparatus will be described in the case where the temperature of the measuring object is To and the emissivity is C.

If the radiant energy per unit wavelength emitted by the measurement object (1) is Eλ, then in the microwave region, from the Rayleigh-Jeans equation.

The relationship n expressed by Eλ=λ·8To (Kλ is a constant) holds true, and the antenna temperature of the measuring antenna - (brightness temperature in radiation temperature measurement)% In other words, when the antenna signal is TA.

TA=tT.

The relationship expressed by is established.

n reference noise source obtained from the reference noise source (2),
In other words, if the reference signal is 'rs, selector switch α
By driving 0 with the clock pulse generator α■,
The antenna signal TA and the base signal Ts are alternately input to the radiometer (1). These input signals are the first. After high frequency amplification by the second RF amplifier (2+ (4)), detection by a square law detector (5), low frequency amplification by a video amplifier (6), and output.

When there is a difference between the antenna signal TA and the reference signal Ts (!:), the frequency component of the clock pulse appears at the output of the video amplifier (6), so when this n is synchronously detected by the lock-in amplifier, the antenna signal TA An output V is obtained that is proportional to the difference between
holds true. However, G is the gain of the radiometer (1),
TOI represents the equivalent noise signal (temperature) for the sum of the internal noise of the measurement system and the output offset.

Here, the gain G and the reference signal Ts.

And if the equivalent noise signal T01 is constant, the above formula % formula %
) The antenna signal TA is found from the output V.

However, as is clear from the above-mentioned relationship TA=aTo, unless the emissivity 2 is known, the temperature To of the measurement object (1) cannot be determined. Therefore, when using such a conventional method [1], accurate temperature measurement could not be performed when the radiation superposition varied or was unknown.

Therefore, as a measurement method to obtain accurate measurement results regardless of fluctuations in the emissivity of the measurement target, a cavity is provided facing the measurement target, and the opening of the cavity is changed using a rotary selector on the top of the cavity. There is a method of simultaneously measuring the emissivity and temperature of a measurement target. However, in order to determine the emissivity, it is necessary to set up the above-mentioned complicated device around the measurement object.

Unless the reflectance of the inner surface of the device is increased, measurement cannot be performed with sufficient accuracy, and this method could not be easily adopted.

In addition, as another method to obtain accurate measurement results regardless of fluctuations in emissivity, we use a comparative hot plate and Kirchhoff's law, which states that the sum of the emissivity and reflectance of the measurement object is 1. There is also a method of performing signal processing using the same method, but it has not yet been put to practical use because controlling the temperature of the comparative hot plate itself is difficult.

Note that a method using a radiometer in the microwave region is already known as a measurement method that is less susceptible to the effects of dust, gas, water vapor, etc. around the measurement object.

[Summary of the invention]

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a non-contact temperature measuring method and a measuring device that can accurately measure temperature without being affected by emissivity. .

In order to achieve the above object, the temperature measurement method according to the present invention alternately transmits an antenna signal from a measurement antenna directed to a measurement object and a reference signal from a reference antenna directed to a reference body with a reflectance of 1 to a radiometer. While inputting the signal, the attenuation rate between the radiometer and the reference body is set to a predetermined value, and the noise signal flowing from the radiometer side to the both antenna sides is adjusted. The method is characterized in that the temperature of the object to be measured is determined by measuring the output of the radiometer while making the signals equal in magnitude.

In addition, the temperature measuring device according to the present invention includes a measurement antenna directed toward a measurement object, a reference antenna directed toward a reference object having a reflectance of 1, a first input terminal connected to the measurement antenna, and a second input terminal connected to the measurement antenna. A changeover switch connected to a reference antenna and having an output terminal connected to the input side of the radiometer, a lock-in amplifier connected to the output side of the radiometer, and applying a clock pulse to the lock-in amplifier and the changeover switch. a clock pulse generator, a noise signal source that provides a noise signal to the output terminal of the changeover switch, transmission of the noise signal from the noise signal source to the output terminal, and transmission of the input signal from the output terminal to the radiometer. A circulator is inserted between the reference antenna and the second input terminal, and the value obtained by raising the attenuation rate to the next power is the attenuation of the noise signal when reflected by the measurement object. a first attenuator whose value is equal to the reciprocal; and a first attenuator between the circulator and the noise source so that the input signal from the output terminal to the radiometer is a constant value regardless of the connection state of the changeover switch. A second attenuator inserted therein, and a signal processing section that controls the attenuation rate of the second attenuator and calculates the temperature of the measurement target from the output of the lock-in amplifier. do.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment of a temperature measuring device according to the present invention.

In the figure, a radiometer (1), a changeover switch α0. The clock pulse generator α3, the lock-in amplifier α, and the measurement antenna C1] may be constructed in the same manner as in the conventional device (see FIG. 4). The first input terminal (IOA) of the selector switch (10) is the measurement antenna a.
The measurement antenna αη has a temperature T9 and a reflectance ε
The second input terminal (IOB) is directed to the reference antenna (3) through the first attenuator (2).
1).

The reference antenna (31) is a reference body (32) with a reflectance of 1.
is directed towards. Further, the first attenuator (1) provides the same effect as attenuation due to reflection spread,
The decay rate is:! :L.

When attenuation due to spherical wave-like expansion upon reflection on the surface of the measurement object is AT o.

1/L” = AT・・・・・・・・・・・・・・・
...The relationship shown in (1) is established.

Connect the input terminal of selector switch 4 (10c) and the radiometer (
A circulator (33) is inserted between the circulator (33) and the circulator (33), which is connected to a noise signal source (35) such as a discharge tube noise source via a second attenuator (34). ing. The noise signal source (35) outputs the second signal from the noise signal source (35).
the circulator (33) via the attenuator (34) of
A noise signal 'I'rec is output towards. The circulator (33) alternately and periodically inputs the noise signal Tree to the changeover switch αq and transmits the signal from the changeover switch αq to the radiometer (1).

Strictly speaking, the noise signal T'rec must also take into account the radiation from the transmission path output of this noise signal Tree, and in that case, the noise signal T'rec is rather output from the output terminal (IOA). is the value of Further, the second attenuator (34) is a variable attenuator, and by controlling its attenuation rate, the noise signal Tree can be tampered with.

The blade signal of the radiometer (1) is processed by a signal processing section (36).
), and is also input to the signal processing section (36) via the lock-in amplifier α4.

This signal processing section (36) controls the second attenuator (34) based on the signal directly input from the radiometer (1).
It also controls the input from the lock-in amplifier (14).
The temperature To of the measurement object (1) is calculated based on the signal.

Next, the temperature measuring method of this embodiment will be explained.

Assume that the connection between the first input terminal (IOA) and the output terminal (10c) of the changeover switch αQ is now closed. At this time, the reflectance of the measurement target is γ, and the ambient temperature is T.
R, the measurement antenna a〃 is a signal (temperature) εT due to the radiation of the measurement object itself.

and the reflected signal γATTr by the surface of the measurement antenna (the measurement target of the noise signal Tree radiated from the 1υ side).
ee and a signal γ(1-AT) TR which is the ambient temperature TR reflected by the surface. Therefore, the patent TAI = gT6 + γAtTrec + r (1-
AT) TR-(2J is established.

Also, the measurement antenna C1υ is connected to the first input terminal (IOA).
Let Ti1 be the measurement signal input from the side.

Since there is no attenuation between the measurement antenna αυ and the input terminal (10,), Til = TA, (3
) holds true.

This time, the selector switch αq switches and the second input terminal (
IOB) (!: Assume that the output terminal (10c) is closed. At this time, if the noise signal received by the reference antenna (31) is TA, the reference body (32) has a reflectance of 1.
In other words, since the emissivity is zero, there is no need to consider the radiation signal from the reference body (32) itself, and TAX = Tree/L + (1-1/L) Ty
t--(4) holds true. In equation (4), the first right-hand side
The term represents the contribution of the noise signal T'rec, and the second term on the right side
The term represents the contribution of the attenuator.

At this time, let Th be the reference signal input to the second input terminal (IOB).

Ti*=TA2/L+(11/L)TR・・・・・・・
...(5) holds true. In equation (5), the first term on the right side represents the contribution of the signal TA2 received by the reference antenna (31), and the second term on the right side represents the contribution of the attenuator.

When TA2 f is eliminated from the above equations (4) and (5), Ti2 = Trec /L” + (1-1/L2)
TR=-=-= (6) is found. Here, L is the attenuation rate of the first attenuator (30), and there is a difference between this attenuation rate and the attenuation AT of the surface reflection of the measurement object (1) as shown in the equation (1
) Since there is a relationship (1/L”=AT), using this formula (H relationship), from formula 1 (6).

Ti! == AT Tree + (1-AT) T
R--(7) is found.

Next, the second attenuator (34) is controlled to adjust the noise signal so that the relationship Ti+=Ti2 is established.

That is, from equation 1 (2) and equation (3).

Ti1=g'ro+γAT Tree 10r (1-A
Since T ) TR-(a) can be found, let us assume that the right sides of this equation (8) and the above equation (7) are equal.

t To-4-I Ay Tree+γ(I AT)
TR=A+Trec+(IAT)TR is found. This
If you organize it.

(1-γ) AtTrec == a To (1-γ
) (I AT)TR・(9) is found. However, 1
Since there is a relationship of −γ=C, using this, equation (9) becomes as follows.

a ArTrec= aTo -t (1-AT)TR
・=・(10) Divide both sides of this 2〇〇 by the emissivity ε.

By adjusting the noise signal Tree so that ATTree = To-(1-AT) TR.

'rt,:T't2 holds true. To find 'ro at this time, just substitute the equation Q time into equation (2), and the result is:

The following formula holds true.

TiI== Ti2=T(,・・・・・・・・・・・・
・・・・・・・・・(12) Therefore, radiometer (1)
The signal from the circulator (33) side that is input to the
Regardless of the value of the emissivity ε of the measurement object (A), it is always equal to the temperature To of the measurement object (1). At this time.

A value (aTo+b) which is not affected by the radiation weight is obtained as the output of the radiometer (1), and from this value, the temperature 'ro is calculated by the arithmetic processing of the signal processing section (36).

According to this embodiment, the temperature can be accurately measured even when the emissivity e of the wire to be measured varies or is unknown.

In addition, by adopting a radiometer (1) that uses microwaves, it is less affected by the presence of dust, gas, water vapor, etc.

This has the effect of widening the measurement temperature range (room temperature or higher).

Therefore, it is now possible to accurately measure the temperature of molten steel in the steel process and accurately measure the temperature of low-temperature objects, which was previously extremely difficult due to fluctuations in the emissivity of the measurement target and the presence of dust, gas, water vapor, etc. in the measurement environment. Furthermore, it has the effect of allowing accurate temperature measurement of corrosive liquids for which thermocouples cannot be used.

Further, the response time can be secured within 0.2 to 0.3 seconds, and there is an effect that it can be adopted in an actual production line without any problem.

FIG. 2 shows the effects of this embodiment in comparison with the conventional method. Since the conventional method measures only εT0, the measurement results differ between water and saline, which have different emissivities ε.

On the other hand, in the case of this embodiment, the temperature -
It can be seen that the termination curve of the radiometer output is uniquely determined.

In addition, using a radiometer in the microwave region, ε+
As a temperature measurement method using the relationship γ = 1, there is a method shown in Japanese Patent Application Laid-open No. 113381/1983, but this conventional method requires that the antenna and the object to be measured are in contact or that the solid angle of the antenna facing the object is 4π. This measurement method is different from the present embodiment because it does not take into account the attenuation AT due to the spread of reflection on the surface of the object to be measured.

FIG. 3 shows an embodiment other than the above. In this embodiment, a distance sensor (40) is provided to measure the distance between the measurement target and the measurement antenna αυ, and a first attenuator (40) is provided.
1) is a variable attenuator.

In the embodiment shown in FIG. 3, attention is paid to the fact that the attenuation AT due to reflection spreading due to surface reflection of the measurement object depends on the distance between the measurement antenna α and the measurement object (1), and the distance is varied. In this case, the distance measurement signal from the distance sensor (40) is input to the signal processing unit (36), and the signal processing unit (36) controls the first attenuator (41), thereby controlling the distance. This also solves the influence of fluctuations on measurement accuracy.In addition, when the ambient temperature fluctuates significantly, the temperature TB
Two reference noise sources (emissivity 1) of 1 + TBl are measured with the measurement antenna αυ, and the radiometer (1) at that time is
Determine the output signal Vs t "z f.

Calibration may be performed by determining a and b using the relationships shown in the explanation of the prior art described above, such as Vl = a TBl + b V2 = a TBl + b.

However, in order to save the trouble of such calibration, the entire structure except for the antennas (11) and (31) may be kept at a constant temperature in a constant temperature bath.

〔Effect of the invention〕

As described above, the present invention can provide a non-contact temperature measuring device and a temperature measuring device that can accurately measure temperature without being affected by the emissivity of the object to be measured.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the temperature (til + constant) device according to the present invention. FIG. Fig. 4 is a block diagram showing a conventional example. (1)... Radiometer, (1q... Changeover switch, α and... Measuring antenna, αJ... Clock pulse generation device, α◆...lock-in amplifier, wire...measurement object, (η(41)...first attenuator, (31)...
Reference antenna, (32)...Reference body, (33)...
・Circulator, (a4)...Second attenuator, (
35)... Noise signal source, (36)... Signal processing section. Patent applicant: Nippon Kokan Co., Ltd. Inventor: Hide Makabe
Hara 1) Kiyoma Nao, Kiyotaka Imai, Patent Attorney, Masaru Yoshihara, Attorney at Law.
Kiyodai Takahashi 1
Figure (ε, TO) 2nd figure 3rd figure (ε, To), 20 Procedural amendment (voluntary) Showa/) 718072 days

Claims (4)

[Claims] (1) While alternately inputting an antenna signal from a measurement antenna directed toward the measurement target and a reference signal from a reference antenna directed toward a reference object with a reflectance of 1 to the radiometer, The antenna signal and the reference signal are made equal in magnitude by setting the attenuation rate between them to a predetermined value and adjusting the noise signal going from the radiometer side to the both antenna sides. A method for measuring temperature using a radiometer, characterized in that the temperature of the object to be measured is determined by measuring the output. (2) In claim 1, when the distance between the measurement object and the measurement antenna changes, the attenuation rate between the measurement object and the measurement antenna is adjusted to increase the magnitude of both signals. A method for measuring temperature using a radiometer, which is characterized in that the temperature is maintained in an equal state. (3) A measurement antenna directed toward the measurement object, a reference antenna directed toward a reference body with a reflectance of 1, and an output terminal whose first input terminal is connected to the measurement antenna and whose second input terminal is connected to the reference antenna. a changeover switch connected to the input side of the radiometer; a lock-in amplifier connected to the output side of the radiometer; a clock pulse generator that provides clock pulses to the lock-in amplifier and the changeover switch; A noise signal source that applies a noise signal to the output terminal of the changeover switch, and transmission of the noise signal from the noise signal source to the output terminal and transmission of the input signal from the output terminal to the radiometer are performed periodically. A circulator is inserted between the reference antenna and the second input terminal of the changeover switch, and the square of the attenuation rate is equal to the reciprocal of the attenuation when the noise signal is reflected by the measurement object. and a first attenuator inserted between the circulator and the noise source so that the input signal from the output terminal to the radiometer is a constant value regardless of the connection state of the changeover switch. A radiometer characterized in that it has a second attenuator and a signal processing section that controls the attenuation rate of the second attenuator and calculates the temperature of the measurement target from the output of the lock-in amplifier. Temperature measuring device. (4) In claim 3, a distance sensor for measuring the distance between the measurement target and the measurement antenna is provided, and the first attenuator is controlled based on the signal obtained by the distance sensor. 1. A temperature measuring device using a radiometer, characterized in that the temperature measuring device is configured such that the influence of variation in attenuation amount due to reflection spread in the measuring object is removed.