Vol.3 No.1 2010

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Research paper−26−Synthesiology - English edition Vol.3 No.1 pp.26-42 (Jul. 2010) thermometers for this temperature range, it is necessary to build a temperature standard traceability system for thermocouple calibration.In Japanese industry, the standardization of the calibration and the testing method on thermocouples has been started in a relatively early times, leading back to the 1960s, when numerous investigative researches and joint experiments were performed by academic societies and industrial associations to ensure the reliability of temperature measurements One of the achievements was a method for calibrating the noble metal thermocouples using the melting point of palladium (1553.5 °C). The driving force of this development was the iron and steel industry that required measurements of the molten steel temperature at around 1500 °C with a precision of approximately 2 °C. Another achievement was a joint research for establishing a calibration method for the noble metal thermocouples based on the temperature fixed point Term 2 up to 1100 °C. This joint research was motivated by an increased demand in the semiconductor-process industry in the 1980s, for fulfilling the technical requirements for the Class 1 thermocouple[1], the highest precision standard as designated by the International Electrotechnical Commission (IEC) for the temperature range up to around 1100 °C.While, on one hand, such efforts were made in industry, it had been regrettable on the other hand that the national measurement standards that should be the reference were not sufficiently prepared at the time. There was, therefore, no way to verify either the calibration methods developed by industry or the reliability of thermometers calibrated 1 IntroductionThis paper describes in the framework of “synthesiology” about the development of the national measurement standard for a temperature range of 1000 °C to 1550 °C, and the establishment of a system that disseminates these temperature standards to the users in the field via the calibration laboratories, as a response to the rising demand from industry for the improvement of reliability of temperature measurement. Measurement standards will never find its importance until it is widely used in society. To implement a system that enables every on-site measurement to be traceable to the national standard, a system design that combines both the technologies that are currently available and those newly developed should be desirable. In this paper, the construction of a high-temperature standard system is discussed in detail, by focusing on the technological background of a newly developed transfer standards. We present the process of designing and forming such a standard system, by selecting the optimum among various scenarios upon the background, choosing the essential elements for ensuring high reliability of temperature measurement, and actually integrating these elements to accomplish our objective. 2 Social demands for high temperature measurementThe temperature range from 1000 °C to 1550 °C is important for the material (iron, steel, etc.) industries, the heat-treating process in the parts manufacturing industries and the semiconductor process industries. Considering the fact that thermocouplesTerm 1 are the most commonly used - Establishing the temperature standards and calibration system for thermocouples -Masaru Arai*, Hideki Ogura and Masaya IzuchiNational Metrology Institute of Japan, AIST Tsukuba Central 3, 1-1-1 Umezono, Tsukuba 305-8563, Japan *E-mail : Original manuscript received September 1, 2009, Revisions received January 25, 2010, Accepted February 5, 2010 Since late 1990’s, the reliability of temperature measurements at high temperatures was remarkably upgraded by establishing the national measurement standards for calibration of thermocouples up to 1550 °C, and by implementing the traceability system. The traceability system, structured as a hierarchical link of calibrations between the national measurement standards and practical measurements, was designed in consideration of various elements such as availability of the measurement standards and sharing the responsibility with accredited calibration laboratories. The optimized scheme for industries in Japan was established by promoting a balanced combination of conventional techniques held by accredited calibration laboratories and progressive technology, taking into account the spread of the progressive technology.Improving the reliability of temperature measurements up to 1550 °CKeywords : Thermocouple, measurement standard, calibration, temperature fixed point, eutectic point[Translation from Synthesiology, Vol.3, No.1, p.1-15 (2010)]

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