DE1648233B2 - Method and device for measuring the true temperature of any radiator - Google Patents

Description

The invention relates to a method and a device of the type mentioned in claims 1 and 3 above.

In the case of non-black bodies (emissivity E <1), partial radiation pyrometers (am "Black body" calibrated) measured a temperature, which is lower than the true temperature. The correction for a free radiating surface is strongly dependent on the type and surface of the body and on the intermediate medium. A minor correction requires color pyrometers that form the luminance ratio of two (single-color) partial radiation (Luminance photometric quantity of the radiance ß): because they give approximately its true temperature regardless of the emissivity £ of the emitter on, if this is a gray emitter (emissivity with the gray emitter is in a wide range Wavelength range independent of wavelength) (literature on the above explanations: K. Mütze, "ABC of Optics" (1961). Verlag Werner Dausien, p. 268 and p. 866 to 873).

»Wien's approximation« is intended to mean that Wien's radiation formula is valid in the range λ · T <3 mm · degrees Kelvin ("K), T < 4000 degrees Kelvin (K).

For decades, more precisely since 1936 at least, there have been color pyrometers in which the ratio two partial radiations is formed (communication from the Kaiser Wilhelm Institute f. iron research. 1936. Düsseldorf, "Stahleisen", p. 21; "Steel and Iron". 1936. Düsseldorf, »Stahleisen«. P. 497 [u. 1950, p. 22]). The radiation laws have been known since 1923 (Planck, »The Derivation of Radiation Laws«.

Leipzig 1923 [Ostwald's class. the ex. Science .. Vol. 206], Akad. Verl.-Ges .; Pohl, R. W .. "optics". Berlin 1940, Springer). However, there was no procedure for the formation of a correction in the determination of the true temperature of a radiator: accordingly one was so far, if the spectral radiance is used for temperature measurement or if the total radiation (integral Radiance) of a radiation source was used, each dependent on special Correction values can be taken from diagrams or first of all to determine the emissivity separately and from this to conclude the true temperature of the examined radiator (aforementioned book "ABC of Optics", p. 872).

In a known device, a spectrally different radiation is used to measure a partial spectral radiation Partial radiation of the same measurement object is used for comparison and a ratio of the two Partial radiation formed (German patent specification

i 648

957 604). For evaluating electrical signals received, whose amplitudes are proportional to the measured radiance, which in turn depends on the distribution of energy according to the Planck function, through the Products of the coefficients of radiation and ·. Permeability (or emissivity and Degree of transmission ι be determined. The "influence of a change in these quantities" is measured in the measurement not taken into account. Therefore, only one relative time * is determined for the partial radiation to be measured. ,,,

On the basis of the method mentioned at the beginning and last mentioned, the invention is based on the object of creating a method and a device which accomplish the determination or measurement of the true temperature of a radiator according to the sources of its own thermal radiation, including that of inaccessible objects, the emissivity and / or transmittance of which changes in the course of the measuring volume. You should take control of the de; Permeability and the measurement of the true temperature also _{: o} guarantee when the measured radiation passes through an intermediate medium with a changing degree of transmittance. Furthermore, the device intended for measuring the true temperature should have a high accuracy. Stability and reliability in spite of very simple _s expansion work.

According to the invention, the solution consists in the method characterized in claim 1 above. The beam densities of radiation with different spectral composition corresponding _ ₁₀ the signals can be obtained by measuring the outgoing radiation from the emitting face and the radiation supplied by a Vergleic'usquelle.

The difference between the temperature measured with any radiation pyrometer and the true temperature is determined, as known from the radiation laws, by the size of the product of emission and transmittance. Every temperature of a blackbody is assigned a certain radiance at a certain wavelength. The radiance in front of the radiation receiver is a function of the aforementioned product. If consequently signals proportional to the radiance of the partial beams are formed and subsequently each 45 g of these signals is raised to the power of an exponent which is proportional to the wavelength value of its radiation current ^; st (cf.Wien's radiation formula), the ratio of the potentiated signals for the purpose of generating a resulting signal is determined so that it is only determined by the values of the emissivity of the controlled radiator and the permeability of an intermediate medium and is independent of body temperature. After pre-calibration, the resulting signal can serve as a correction for one or more of the radiance signals for determining the true temperature.

The apparatus for measuring the true temperature according to the present method is in the Claims 3 to 6 characterized. f> o

The invention is described below with reference to the exemplary embodiments shown in the drawing explained in more detail. It shows

F i g. 1 eir block diagram of the device according to the invention, (> 5

F i g. 2 a variant of FIG. 1, Fig. 3 eir. Setup as in FIG. 1 or 2, but with a logarithmic device,

F i g. 4 a device as in FIG. 1, but with Commutator,

F i g. 5 shows a common variant of FIG. 3 and 4.

In the device according to FIG. 1, the following are arranged in the direction of signal flow: an optical unit 1. which picks up the radiation current from the radiator (not shown), a mono-chromating device 2 (light filter, prism, diffraction grating) which eliminates the radiation currents with the required spectral composition. Radiation receiver 3. which consist of one or more cells (photocell, thermocouple, bolometer Li. A.'i and which convert the radiation currents with a corresponding spectral composition into electrical signals, a function converter 4, which is set up to exponentiate signals at the signal receiver output . which are proportional to the values of the effective wavelengths, a quotient circuit S. at which the output cm resulting signal is obtained, which is determined by the ^{variation of the} radiance signals generated at the output of the functional converter - 4, a corrector 6 converts the resulting signal of the ratio value generated at the output of the quotient circuit 5 into sianals, the values of which determine the corresponding correction values for determining the true temperature, a display device 7. which registers the correction values for determining the true temperature or the true temperature itself. A converter 8 converts the radiance signals corresponding to the radiations of different spectral composition into a signal of the conditioned temperature (color. Black-. Partial or total radiation).

If the device described is only used to control the emissivity of a radiator and the The transmittance of an intermediate medium is used, but the measurement of the true temperature is not required. so the corrector 6 and the converter 8 from the in F i g. 1 shown Block diagram can be removed. In this case, the radiance ratio signal from the quotient circuit output are fed directly to the display device 7, which in this case is used directly as a display device of the emissivity or the degree of transmission functions.

The mode of operation of the device according to FIG. 1 is explained below.

The values of the radiance (brightness) for two spectral ranges. which have been eliminated by the mono-chromating device 2 from the radiation current with the effective wavelengths A ₁ and A- are referred to as milB [A ₁ . T) and B (A _2. T) (DlN 1349. DIN 5031). where 7 '- means the value of the true temperature of the controlled radiator; the emissivities of the radiator are denoted by <(/.,) and MA ₂ ) »and the transmittance of the intermediate medi" ms with T (A ₁ ) and τ | Α ₂ ).

Then the expressions for the radiance can be written down as follows:

B (A ₁ T) = B ₀ (A ₁₅ T) Kz ₁ ) T (A ₁ ),
B (A ₂ T) = B ₀ (A ₂ , T), (A ₂ ) τ (A ₂ ),

here, B ₀ (A ₁ , T) and B ₀ (A ₂ , T) are the corresponding values of the radiance for the same wavelengths of the radiance of a blackbody having the temperature of the radiator.

The coefficients of the spectral sensitivity of the radiation receiver 3 are denoted by 5 and ΐ _2.

For the wavelengths A ₁ and A ₂ , the following signals X, can be derived at the input of the function converter 4 in the area of the Wien approximation:

X ₁ = i, C ₁ /,

A ₁

X ₂ = I ₂ C ₂ A ₂ " ⁵ " - (A ₂ ) τ (Α ₂ ) exp - - ^.

Here is C ₁ = 3.732 ■ 1ϋ ~ ⁵ erg. ^{Cm 2} · s' \ C ₂ = 1.4388 cm-degrees (Hut I, p. 395).

The y, signals at the output of the function converter 4 are with the X, signals at the converter input through the function

Y ₁ = κχ'γ

tied together.

Consequently, the signals at the input of the quotient circuit 5 are given by the expressions below shown:

Y ₁ = K ξ? CZ ¹ Z- (A ₁ ) / ¹ U ₁ ). ; .f ^5; 'exp- ^,

Y ₂ = Xi ^ C ^ AA ₂ ) / MA ₂ ) / Γ ⁵ &quot; exp- ^.

The resulting signal at the output of the quotient circuit 5 is used as the size of the ratio

Z _1-2 =

obtain.

* Z = (A ₂ ) τ "(Α ₂ )

Values is T _x + IT = T, where T indicates the value of the true temperature.

As a result, the display device 7, to which the signals Q and N are applied simultaneously, will display (or register) the values of the true temperature of the controlled radiator.

If you do not need to measure the real temperature, values of the or the resistance the emissivity of the radiator as well as the

ίο The degree of transmission of the intermediate medium can be checked directly by the values of the Z ₁₂ signals. In Fig. 2 is an embodiment variant of the device according to FIG. 1 shown. The units 1, 2, 3, 5, 6, 7 and 8 are the same as for the one

i _S direction in Fig. 1.

From the radiation receiver3 they become the three or signals corresponding to several currents, likewise of corresponding spectral composition Multiplier 9 is supplied, from the output of which the multiplied signals reach the quotient circuit 5, which generates the resulting ratio signal in which the sum of the frequency factors in the numerator is equal to the sum of the frequency factors in the denominator.

The resulting signal is fed from the output of the quotient circuit 5 to the corrector device 6, after which the structure of the block diagram does not differ from that in FIG. I illustrated.
If the true temperature does not need to be measured, the units 6 and r from the circuit diagram in FIG. 2 can be removed.

In the block diagram according to FIG. 2 are determined by the values of the radiance B {?. _h T), the three or more ren, z. B. four radiation streams with effective wave lengths A ₁ , A ₂ , A ₃ and A ₄ correspond,

B (A ₁ , T) = _r (A ₁ , T) t (A "T) B ₀ (A ₁ , T),

B (A ₂ , T) = f (A ₂ , T) τ (A ₂ , T) B ₀ (A ₂ , T),

B (I ₃ , T) = _r (A _3. T) t (A ₃ , T) B ₀ (A ₃ , T),

B (X ^ T) = f (A ₄ , T) T (A ₄ , T) B ₀ (A ₄ , T) ,

The following signals are generated at the output of the radiation receiver 3:

= const.

From this it follows that the resulting signal Z _1-2, if the facility _{parameters f, and ξ 2 are} constant, is only determined by the values of the emissivity of the controlled radiator and the transmittance of the intermediate medium and is independent of the temperature of the radiator within the scope of the Wien approximation .

Going through precalibration of Temperaturkorrektionswerte - has correspond .it, the specific sizes of the signal Z _1-2 is obtained, then the output of the corrector is 6, the signal Q ^ JT generated if both or one of the further sealing beam signals X ₁ at the same time the converters 8 are supplied, the signal N is obtained at the converter output, which characterizes the values of the temperature (the black body, partial, total or color radiation), ie N = T _x . The algebraic sum of Ci = ^ ₁ C ₁ A ₁

" ⁵

A ₁ T '

f ₂ = I ₂ C ₁ A ₂ - ⁵ ε (z ₂ , T) t (A ₂ , T) exp - ^ r,

X ₃ = f ₃ C ₁ A ₃ - ⁵ ε (Α ₃ , T) r (A ₃ , T) exp - - ^ - ,

X ₄ = I * C ₁ Af ⁵ f (A ₄ , T) T (A ₄ , T) exp - -

A ₄ T

The ratio between the wavelengths of this spectral radiance is designed so that

/ f ¹ + A ₂ - ¹ = A ₃ - ¹ + A ₄ - ¹ = Ji ₀ - ¹
is; now the signals X ₁ - in pairs to the mull

7 ^w 8

Applicator 9 is supplied, so two signals P, ₂ and P _{1-4 are obtained at the output of the latter}

/ », _-2 = ß'V, .V ₂ =

= BX ₃ X ₄ =

A.,. T) '(A ₄ , T) T (A ₃ , T) r (/ _n .T) exp-,

where B = const.

If the signals P _1-2 and P _3-4 is the quotient circuit 5 supplied from the output of the multiplier 9, is obtained at the output of the latter, the resulting signal Z ₁ _ ₄ whose value does not depend on the temperature of the controlled radiator.

Indeed it is

SiUA% '(A ₃ Ti, (Z ₄ T) t (A ₃ , T) t (^ T)'

If the characteristic values £ _{1 , £ 2} , £ ₃ , f _{4 are} constant, the signal Z 1 _ _{4 is} exactly as in the device according to FIG. 1 does not depend on the temperature of the radiator, this signal is determined by the emissivity of the controlled radiator and the permeability of the intermediate medium. A pre-calibration allows, as shown in FIG. 1 to receive a signal at the output of the corrector 6, which determines the quantity IT, at the output of the converter 8, however, a signal that determines the values of the reference temperature.

Similar values can also be used for three wavelength values, e.g. B. under the condition Af ^! + A ₂ "'= A ₃ ' and so on.

The radiance signals taken from the radiation receiver 3 are generated according to a variant the device (FIG. 3) is fed to the logarithmic device 10. From the output of the device 1 « the logarithmized signals reach the converter 4, which sends the radiance signals to the corresponding Exponents raised to the power. Since the logarithms of the signals are available at the output of the device 10 are, the potentiation is done here simply by multiplying by the factor that is required Corresponds to exponent. The multiplier 9 works in the block diagram according to FIG. 3 as a multiplier and Quotient meter. If the logarithmized signals are fed to it in phase, this is also done Multiply the signals together. When the signals to the input of the multiplier 9 are in antiphase are supplied, the ratio of these signals is obtained at its output.

The corrector 6 and the display device 7, as well as their functions, are those in FIGS. 1 and 2 similar.

In the block diagram according to FIG. 3 are from the converter 8 not the intensity signals themselves, but their logarithms in signals for determining the reference temperature converted This way turns out to be very effective.

The units 6 and 8 in the block diagram of FIG. 3 can, as in the circuits of FIG. 1 and 2 are removed if only the control of the emissivity and permeability is required is.

In the facility according to Fig. 3 the signals of the radiance at the output of the receiver 3 are vorlogarkhmiert by the device 10; signals in the following form are obtained at its output /, · = In X; At the output of circuit 4, the signals are given by the expressions r _t = Aj /, - = A ₁ - In X, if at most two spectral radiance levels are present.

In the case of three or more spectral beam dichroes with the above-mentioned frequency ratio, a conventional linear four- or two-pole can be used as converter 4, at the output of which the following signals are available r _f = ic /, = k In X, where

If no more than two radiation currents with wavelengths A _t and A ₂ are used, the signals T ₁ = A ₁ In X ₁ and r ₂ = A ₂ In X _{2 are} fed from the output of the converter 4 to the multiplier 9 in antiphase. _{The resulting signal ZJ -2} = r, - r _{2 is} then obtained at the output of the multiplier 9

as the logarithm of the ratio Zi _-2 = In - ^ -.

According to the value of the signal Zj _-2 , the generation of the signal Q = IT at the output of the corrector 6 is carried out similarly to the previous explanations (by pre-calibration).

It is obvious that in the block diagram of FIG. 3 the signals at the output of the converter 8 as a result of pre-logarithmization by the device 10 proportional to the reciprocal values of the black or Color temperature can be specified, which is very advantageous in practice

When using the device according to FIG. 3 for three or more spectral radiance is the exponentiation of Α, - as well as for the device according to FIG. 2 not mandatory. With λϊ ^ι + / J ¹ = Af ¹ , the resulting signal at the output of the multiplier 9 can be obtained as the following expression

7 -

4-

+ A ₂ " ¹ = A ₃ " ¹ +

is

ε U ₃ T)

AU

In Fig. 4 shows a further embodiment of the invention. By means of the radiation interruption 12, radiation flows alternately from the controlled radiator via the optical unit 1 and from the built-in reference _{source 11 to the monochromatizing device 2} and then, 0 to the radiation receiver 3. The radiation currents from both sources are fed to the radiation receivers and then pass from their output to the function converter 4. From the output of the converter 4, the radiance signals raised to the power of the required exponent, _{5, are} fed to the commutator 13, the effect of which is connected to the function of the radiation interrupter 12 by means of the synchronizer 14. From the output of the commutator 13, the signals raised to the power of the required exponents are fed from both receivers to the quotient circuit 5 in appropriate phases. The type of application of the units 6, 7 and 8 does not differ from that in the embodiments described above, which are shown in FIGS. 1, 2 and 3. If the true temperature does not need to be measured, the corrector 6 and the converter 8 can be removed.

The advantage of the in F i g. 4 embodiment shown consists in the high stability due to the elimination of the Influence of transfer factors of individual units, including the influence of the values of the spectral sensitivity of the radiation receiver.

Here, by means of the radiation interrupter 12, alternating radiation currents arrive from the controlled one Emitter (via the optical unit 1) and from the built-in comparison source 11 to the monochromatizing device 2 and then to the radiation receiver 3.

In the first case, the following signals are obtained at the output of the receiver 3 for spectral ranges with effective wavelengths A ₁ , A ₂ ... χ, -

(A ₄₁ TJt (AjJ-

X; = - ^£ 2

i. T),

- ~ u. s. f.

-γ =

x; = - i, C ₁ x \ " ⁵ / (/,) exp -— ■ ■

/, ι

At the output of the converter 4, the signals from the controlled radiator are correspondingly V, = XV ₁ ". Ie

Y ₁ = K i, ¹ x C ₁ ¹ 'Af ^5; / ¹ Ui) 1 * U ₁ ) exp --γ

Y ₂ = Ki ₂ ¹

) T ^h (A ₂ ) exp - j ¹ etc.

At the output of the converter 4, the signals from the built-in source can be expressed accordingly will be through

Y ₂ = KS ₂ ¹ C ₁ ¹¹

/ ' ¹ U ₁ ) exp -

Ε ^ (Λ) εχρ -

-ψ-

u. s. f.

When the commutator 13 is activated by the synchronizer 14, the signals Y ₁ . Y ₂ - ^ and X ₁ ', Y ₂ ... Υ; the quotient circuit 5 is supplied so that at its output the resulting signal Z ₁ assumes the following form

_ Y ₁ TT ₂ . .. Υ,., Υ ',

Y ₂ - Y ₁ -. ..

For example, Z ₁₂ for two spectral radiances with effective wavelengths A ₁ and A ₂ is expressed by the following ratio:

C ₂

45

X ₂ = ξ ₂ C, A ₂ ⁵ f (A ₂ ) r (A ₂ ) exp - -γ for the built-in source is however

-'Hx ₂ )

= const,

X ₁ = ί, C ₁ Af ⁵ ε (Α,) T (A ₁ -) exp - - ^ -.

In the second case, three streams of radiation from the built-in source 11 reach the receiver, which are any Temperature value T 'and their emissivity the values

It follows from this that the signal Z ₁ ^ (independent of the stability of the circuit units) characterizes the determinants of the controlled radiation current (emissivity and transmittance of the intermediate medium)

Are radiation currents for more than two spec-

and their emis- tral areas, z. B. for three Uf ¹ + A ₂ '= A ₃ " ¹ ) used,

the above-mentioned resulting signal at the output of the quotient circuit (FIG. 4) can be as follows

,) ... e '(A () form can be expressed:

accept.

In this case, the radiance signals are represented by the following expressions:

_ EUiHA ₂ ) T (A) TU ₂ K (A ₃ )

i = J ₁ C ₁ Ar ⁵ AX ₁ ) exp In addition, the operation of the device differs according to FIG. 4 does not depend on the operation of the types of exhaustion described above.

Claims (6)

Patent claims: 1. Procedure for determining the true temperature of any emitter in the approximate range of Wien's radiation formula, from its Radiation at least two spectrally different radiations are eliminated and their Signals proportional to radiance are subsequently set in relation to one another by forming signals to the power of an exponent corresponding to the Value is proportional to the wavelength of the eliminated radiation, then forming the ratio the signals that are only dependent on the emissivity and transmittance and Use of the obtained ratio as a correction for one or more of the radiance proportional signals after a pre-calibration. 2. The method according to claim 1, characterized in that that in the ratio numerator and denominator are represented by products of signals that correspond to the radiance of the individual radiations, and that the sums of the reciprocal Wavelength values in the numerator and denominator are the same. 3. Device for measuring the true body temperature according to the method of claim 1 and 2. contains the payment recipients, which via a gain-> d ~ shaping circuit is coupled to a display device, characterized in that at the output; ng of the radiation receiver (3), which converts at least two spectrally different radiations into signals that correspond to the radiance, the following units are connected one after the other: a function converter (4). suitable for exponentiating each of the signals taken from the receiver (3) according to an exponent, which is the wavelength value of the corresponding eliminated radiation is proportional. a quotient circuit (5), the for the purpose of obtaining a resulting. Signal determines the ratio of the signals mentioned, a corrector (6) which converts the resulting signal into a correction signal for determination after pre-calibration the true body temperature converts, a converter (8), which the output signal to be measured of the radiation receiver (3) to the display device 17). 4. Device according to claim 2, characterized in that the radiation receiver (3) the quotient circuit is suitable for receiving more than two spectrally different radiations (5) is equipped with a multiplier (9) at the entrance. the one at the output of the circuit (5) Ensures the generation of a signal that is the ratio of the products of the radiance is proportional, the wavelengths of which are chosen so that the sums of the reciprocal wavelength values the numerator and denominator are the same. 5. Device according to claim 3 and 4, characterized in that at the output of the radiation receiver (3) a logarithmic device (10) is connected, behind which the logarithmic Beamdiclite signals are fed to a subtraction circuit with a commutator (13) (Fig. 4). 6. Device according to claim 3. 4 or 5, characterized in that in front of the St -. \ Hlungsempfänger (3) a built-in reference radiation source (ll) and a radiation interrupter (12; are arranged and that the radiation interrupter synchronized with the commutator (13) connected to the output of the function converter (4) is. which the corrector (6) receives the resulting signal alternately from the radiation surface and from the built-in reference source (11) feeds.