RU1800295C - Spectral ratio pyrometer - Google Patents

Abstract

Usage: for measuring temperatures that vary widely. Essence: the aperture diaphragm is made in the form of a disk containing a number of equally equidistant distances from the center of the holes, and the total area S 1 of the aperture of the previous range is selected from the CONDITIONS Sz 1 SmaxTk (D Dsop), and the total area of S 2 of the aperture of the subsequent subranges from the correlation -Cg (tn2 THi) SH6NIA -6 YATN1 TH21 Where SmaxTk is the largest area of the holes providing a linear mode of operation of radiation receivers when the error from the influence of the measurement of the level D is less than the permissible value Accuracy of Adop over the entire range; I - the effective wavelength of the longer wavelength range of the pyrometer; TH1 is the initial temperature value of the previous measurement range; TH2 is the initial temperature value of the subsequent measurement sub-range; Sz is a pyrometric constant. 5 silt

Description

The invention relates to techniques for measuring temperature by radiation and can be used in industry and scientific research to measure temperatures that vary widely.

The value depending on the temperature of the object and directly measured by the radiation pyrometer is the electrical signal of the radiation receiver, which occurs when a light stream enters its photosensitive surface in a more or less wide spectral region (for total and partial radiation pyrometers) or the ratio of signals proportional to luminous fluxes of different spectral composition (for spectral ratio pyrometers). When switching from one measurable subrange to another (from lower to higher temperatures), elements limiting the amount of light flux (diaphragms, absorbers, etc.) are used in the pyrometer optical system.

Radiation pyrometers 1 are known, including spectral-relative pyrometers. bars in which diaphragms mounted directly behind the lens with calibrated or adjustable holes are used to adjust the luminous flux.

When moving to the next sub-range of change (higher temperature 00 О

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In addition, the diameter of the calibrated hole is reduced.

A disadvantage of this solution with respect to spectral ratio pyrometers is the effect of chromatic aberrations in the exit pupil of the optical system including the lens and the aperture diaphragm (in the plane of the aperture diaphragm). As a result of this phenomenon, the distribution of the spectral composition of the radiation in the plane of the aperture diaphragm changes, enriched, for example, with shorter wavelengths from the optical axis to the periphery, which leads to an increase in the error. Also known is a spectral ratio pyrometer 2, which can be considered a prototype of the proposed device, comprising a lens, aperture and field aperture, a beam splitter, radiation receivers, a signal ratio meter, an indicator of the measurement result. In this pyrometer, a material aperture diaphragm with a calibrated aperture is installed immediately after the lens to provide the necessary initial value of the luminous flux providing a linear mode of operation of radiation detectors in a given measurement sub-range. The center of the hole is on the optical axis of the lens. When moving to the next measuring sub-range (higher temperatures), the diameter of the hole also decreases accordingly (see Fig. 5, items 17 and 18). This pyrometer has the same drawback, because reducing the diameter of the aperture diaphragm when moving to a higher temperature sub-range. Measurement leads, due to the chromatism of the optical system, to a change in the spectral composition of the radiation incident on it. photodetectors, to a relative increase in the effective wavelengths of the pyrometer and, in combination with higher temperatures, to weakening the dependence of the spectral ratio on temperature (R (T) JT) and, ultimately, to an increase in errors associated with the influence of influencing factors ( changes in brightness level, ambient temperature, etc.).

This disadvantage is especially pronounced in pyrometers with wide measuring ranges, since on the one hand, the dynamic range of signal changes increases and the deviation of the light characteristic from the linear dependence increases, on the other hand, it increases

the d2R / dT value is the second derivative of the spectral ratio of temperature. This last feature is illustrated by the data given in the table, where

the values of the change in the spectral ratio at the beginning and end of two measurement sub-ranges (by 100 ° C) are indicated. Those. a change in the sensitivity of the spectral ratio by temperature of more than 2 times occurred.

The purpose of the invention is to increase the accuracy of temperature measurements with an extension of its measurement range.

The goal is achieved in that

in a pyrometer containing an optically coupled lens, an aperture and field aperture, a beam splitter and radiation detectors connected to a signal ratio meter, the inputs of which are connected to the outputs of the radiation receivers, and the output is connected to the input of the measurement result indicator, the aperture diaphragm is made in the form of a round disk containing r d equidistant on

the maximum possible distance from the center of the holes, and the total area SEJ of the holes of the diaphragm of the previous sub-range is selected from the condition Sj1 SmaxTk (D Dop),

and the total area S52 of the holes of the diaphragm of the subsequent subrange is from the ratio

-G (TH2 -ТН1) 1st ЯТ „1ТН2, (1)

where SmaxTk is the maximum total aperture area of the diaphragm at which the necessary linearity of the signals corresponding to the final temperature of the first subrange is provided

measurement (i.e., in which the error from a twofold change in level A does not exceed the permissible value of Dop);

A is the effective wavelength of the longer wavelength working range of the pyrometer spectrum;

TH1 is the initial temperature value of the previous measurement sub-range;

TH2 is the initial temperature value of the subsequent change sub-range;

Ј2 is a pyrometric constant.

In FIG. 1 shows a functional diagram of the proposed device; in FIG. 2

- views of the diaphragm for the first and second sub-ranges of measurement; in FIG. 3 is the relative (reduced to 1) spectral distribution of production at the input of the optical system and in the plane of the aperture diaphragm; figure 4

- a variety of the proposed aperture

apertures; in FIG. 5 - views of the aperture diaphragm of the prototype pyrometer for two adjacent measurement sub-ranges,

The proposed pyrometer (Fig. 1) comprises a lens 1, an aperture diaphragm 2, a field diaphragm 3. a beam splitter 4, radiation receivers 5 and 6, a signal ratio meter 7, a measurement result indicator 8.

The aperture diaphragm (Fig. 2) contains a number of openings equally equidistant to the maximum possible distance from the optical axis, the total area of which for the previous and subsequent subranges is determined in accordance with the formulas given above. For subbands with a relatively low initial temperature (VT 1000 ° C), the aperture openings are made in the form of truncated sectors (Fig. 4).

In either embodiment, the openings are spaced as far as possible from the center, but do not go beyond the design diameter of the aperture diaphragm of the optical system.

The proposed pyrometer works as follows.

The radiation from the measurement object collected by the lens 1 passes through the aperture diaphragm 2, which compensates for the influence of chromatic aberrations, and is focused in the plane of the field diaphragm 3.

The radiation is transmitted through a beam splitter 4 to radiation receivers 5 and 6, which convert two light fluxes of different spectral composition into electrical signals. The ratio meter 7 measures the ratio of these signals that carry information about the color temperature of the object, the value of which is displayed on the indicator of the measurement result 8. At the input of the optical system, the spectral composition of radiation perceived from the object depends on the temperature and emissivity of the object and is the same regardless of the distance from the optical axis (uniform illumination of the lens). After the lens in the plane of the aperture diaphragm, due to chromatic aberrations, redistribution of rays of various wavelengths occurs, as a result of which the spectral composition of the radiation changes from the original one (Fig. 3 explains this phenomenon). The abscissa shows the relative distance in a plane perpendicular to the optical axis in the direction of the heating axis to the periphery. The ordinate axis is relative (given at the system input to

unit) value of the spectral ratio. Line 11, parallel to the abscissa axis, displays the value of the spectral ratio at the input of the system, line 12 - in the plane of the aperture diaphragm. As can be seen from FIG. 3, the spectral composition of the radiation near the optical axis (region along arrows 13) is depleted in the short-wavelength component, which led to an increase in the prototype

0 errors (increase in effective wavelengths).

The aperture diaphragms shown in FIG. 2.4; For the first sub-range of measurement 5, a diaphragm of type 9 was used, and when moving to a higher-temperature sub-range, a diaphragm of type 10. In Fig. 3, the spectral composition of the radiation passing through these diaphragms is indicated by arrows 14 and 15, respectively. As can be seen from the figure, when passing from the first subband to the second, the total spectral distribution changes due to shorter wavelength radiation, which eliminates the additional errors described above. The smaller diameter of the holes of the diaphragm 10, in comparison with the diaphragm 9, provides

0 decrease in luminous flux upon transition to a higher temperature second sub-range of measurement. The ratio of the total area of the holes in the aperture diaphragms, providing the same

5, the radiation level in the previous and subsequent subbands is determined by the formula (1).

The proposed invention is implemented in a spectrometer spectrometer pyrometer 12. The pyrometer used

0 four-lens lens projecting an image of an object in the flatness of a field aperture. Beam splitting is carried out using a filter installed at an angle to the optical axis, and

5, photodiodes FD24K (short wavelength interval of the spectrum) and FD10G (long wavelength interval) are used as receivers. An analog-digital signal is used as a signal ratio meter

0 photocurrent converter of radiation receivers by the double integration method assembled on microcircuits of the type K561IE80, K561LA7, K561TM2, K561TMZ, K544UD1A.

5

Indicator of the measurement result co-rejection on four digital indicators of the type AOC324.

As an aperture diaphragm for a sub-range of 900-2200 ° C, a diaphragm of the type shown in FIG. 4 with the parameters:

Claims (1)

the distance of the holes from the center (along the centerline) 10 mm the number of holes 4 Width (in the radial direction) 4 mm For the sub-range 1200-3000 ° C, a diaphragm 10 of the type shown in FIG. 2 was used with the parameters: distance of the holes from the center 10 mm, number of holes 10 diameter 2 mm holes. Formula of the invention A spectrometer pyrometer comprising an optically coupled lens, aperture and field aperture, a beam splitter and radiation detectors connected to a signal ratio meter, the inputs of which are connected to the outputs of the radiation detectors, and the output is connected to the input of the indicator of the measurement result, characterized in that, in order to improve the accuracy of temperature measurement, the aperture diaphragm is made in the form of a circular disk containing a number of holes equally equidistant to the maximum possible distance from the center, and the total area S-2.1 aperture of the previous sub-range is selected from the condition  maxTk (), and the total area S & .. 2 holes of the diaphragm of the subsequent subrange is from the relation -G (TH2 -tН1) Sf. .i -e / Gytnz where ZmaxTk is the largest area of the aperture openings providing a linear mode of operation for radiation receivers when the error from the influence of measurements of the level D is less than the permissible error value Ddop in the entire measurement range; I - the effective wavelength of the longer wavelength range of the pyrometer spectrum; TH1 is the initial temperature value of the previous measurement range; TH2 is the initial temperature value of the subsequent measurement sub-range; C2 is a pyrometric constant. TV i S6ЈG08l FIG. S