Calibration of thermometers in the temperature range from −80 • C to 550 • C requires liquid baths; alcohol, water, silicon oil, salt baths and dry block furnaces. In this study, the use of salt baths outside of their usual range of 250 • C to 540 • C for calibrating thermometers in the range between 175 • C and 250 • C is proposed. The calibration range from 150 • C to 250 • C is usually covered by an oil bath, but utilizing a salt bath saves calibration time and resources, improves stability and homogeneity, allows longer term usage of the liquid, and reduces hazardous chemical vapors evaporated at temperatures above 175 • C. This proposal is based on a study of the uncertainty contributions at varying salt bath temperatures in the range from 175 • C to 540 • C which was carried out in this study. Results achieved and analyzed in this study indicate that the implementation of salt baths in this lower temperature range provides opportunities to calibrate reference and/or working thermometers with an uncertainty below 30 m • C, almost the same as the oil-bath uncertainty in the range of 175 • C to 250 • C. The main components of uncertainty contributed by a salt bath over this temperature range are discussed in this study.

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Bu çalışmada direnç termometrelerin kalibrasyonların da ve kontrollerinde kullanılan suyun üçlü noktası hücresinin hazırlanması ve ölçüm belirsizliğinin hesaplanmasına ilişkin detaylı bilgi verilmiştir. Suyun üçlü noktası hücresi Yeditepe Üniversitesi Fizik Bölümü Metroloji ve Kalibrasyon Laboratuvarında (YUKAL) özel olarak tasarlanarak üretilmiştir. Hücrenin hazırlanması aşamasında katı CO2 kullanılarak buz tabakası elde edilmiştir. Katı CO2 yöntemiyle 15 dakikalık sürede hücre içerisinde katı, sıvı ve gaz fazlarının aynı anda elde edildiği bu yöntemle yapılan ölçümler analiz edilerek ölçüm belirsizliği bütçesi oluşturulmuştur.

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Different types of thermometers (resistance thermometers, thermocouples, liquid in glass thermometers, radiation thermometers, etc.) are used in temperature measurements. Resistance thermometers are among the most reliable types of sensors used for sensitive temperature measurements. The traceability, accuracy and precision of the measurement results are important for the reliability of the measurements. There are many parameters that affect the uncertainty estimation in measurements made with resistance thermometers. One of the parameters to be considered in the uncertainty estimation is the interpolation error in converting the resistance value to temperature. Different methods (ITS-90, Calendar Van Dusen CVD, Polynomial equation) can be used to convert the resistance value to temperature. The problem is that there are differences in the temperature values read using the coefficients obtained by different methods. In this study, the effect of errors from CVD and polynomial equation methods on measurement uncertainty was investigated.