Залежність похибки визначення температури пірометрами від коефіцієнта випромінювальної здатності об’єктів
Date
2019-02-26
Journal Title
Journal ISSN
Volume Title
Publisher
Видавництво Львівської політехніки
Abstract
Наведено результати дослідження залежності похибки визначення температури термометрами
випромінення від коефіцієнта випромінювальної здатності досліджуваних об’єктів. Проаналізовано математичні моделі,
які описують залежності між дійсним значенням термодинамічної температури і виміряними пірометрами уявними
температурами, із урахуванням впливу значення коефіцієнта випромінювальної здатності матеріалів. Ці моделі покладено
в основу побудови найпоширеніших типів пірометрів, зокрема: яскравісного, повного випромінення та спектрального
відношення. Описано результати проведених теоретичних досліджень. Проаналізовано доцільність та наведено практичні
рекомендації стосовно застосування певного типу пірометра залежно від коефіцієнта випромінювальної здатності
досліджуваних об’єктів та вимог до метрологічної достовірності результату вимірювання.
Study of the dependence of the temperature determination error on the emissivity factor of materials is conducted in the paper. The mathematical models, which describe the ratio of thermodynamic temperature and measured imaginary temperatures, taking into account the emissivity factor, are analyzed. The constructions of the full radiation, brightness radiation, and spectral ratio radiation pyrometers are underpinned by the considered models. Analyzing the mathematical models of radiation thermometers (or pyrometers), one can observe a fundamental circumstance that interferes with the wide application of pyrometry, namely, lack of knowledge or even the mere absence of information on the true numerical values of the emissivity factor of the objects. When measuring the temperature of objects that fall under the classification of “real body”, there arise serious problems with the reliability of its determination. The vast majority of modern pyrometers, which are calibrated by a blackbody, compute the data received from sensitive element of the pyrometer into temperature values, not taking into account the real value of the object’s emissivity factor. Thus, if the latter is 0.1, and the pyrometer is graded by the blackbody, then, only ~10 % of its radiation energy is perceived by sensitive element of the pyrometer. As result, the determined temperature value is substantially lower than the actual one. It can be argued that the lack of information about a real numeric value of the monitored object’s emissivity factor is the determining source of distortion of the measurement result. The problem is further complicated by the fact that the mentioned factor is the parameter that depends on many factors, and in particular on the temperature, which is exactly to define. The paper presents the results of the study of the dependence of the absolute measurement error of temperature on emissivity factor for different types of pyrometers. The accuracy of measuring the temperature with pyrometric means is minimal only for measuring the black body or gray body by the spectral ratio pyrometers. The error of measuring the temperature of real object differs significantly from the error of the black body. This is due to the ignorance of the true value of the emissivity factor of the real object. Therefore, presetting of this factor in pyrometers that is recommended by most pyrometers guidelines is completely incorrect.
Study of the dependence of the temperature determination error on the emissivity factor of materials is conducted in the paper. The mathematical models, which describe the ratio of thermodynamic temperature and measured imaginary temperatures, taking into account the emissivity factor, are analyzed. The constructions of the full radiation, brightness radiation, and spectral ratio radiation pyrometers are underpinned by the considered models. Analyzing the mathematical models of radiation thermometers (or pyrometers), one can observe a fundamental circumstance that interferes with the wide application of pyrometry, namely, lack of knowledge or even the mere absence of information on the true numerical values of the emissivity factor of the objects. When measuring the temperature of objects that fall under the classification of “real body”, there arise serious problems with the reliability of its determination. The vast majority of modern pyrometers, which are calibrated by a blackbody, compute the data received from sensitive element of the pyrometer into temperature values, not taking into account the real value of the object’s emissivity factor. Thus, if the latter is 0.1, and the pyrometer is graded by the blackbody, then, only ~10 % of its radiation energy is perceived by sensitive element of the pyrometer. As result, the determined temperature value is substantially lower than the actual one. It can be argued that the lack of information about a real numeric value of the monitored object’s emissivity factor is the determining source of distortion of the measurement result. The problem is further complicated by the fact that the mentioned factor is the parameter that depends on many factors, and in particular on the temperature, which is exactly to define. The paper presents the results of the study of the dependence of the absolute measurement error of temperature on emissivity factor for different types of pyrometers. The accuracy of measuring the temperature with pyrometric means is minimal only for measuring the black body or gray body by the spectral ratio pyrometers. The error of measuring the temperature of real object differs significantly from the error of the black body. This is due to the ignorance of the true value of the emissivity factor of the real object. Therefore, presetting of this factor in pyrometers that is recommended by most pyrometers guidelines is completely incorrect.
Description
Keywords
температура, коефіцієнт випромінювальної здатності, пірометр, похибка вимірювання, Temperature, Emission factor, Pyrometer, Measurement error
Citation
Микитин І. П. Залежність похибки визначення температури пірометрами від коефіцієнта випромінювальної здатності об’єктів / І. П. Микитин, П. І. Скоропад // Вимірювальна техніка та метрологія : міжвідомчий науково-технічний збірник. — Львів : Видавництво Львівської політехніки, 2019. — Том 80. — № 1. — С. 34–40.