Effects of air ventilation cap on the calibration uncertainty of air thermometers in climate chamber

Abstract

Abstract Accurate and reliable air temperature measurements are essential in many scientific and industrial applications. The calibration of temperature sensors in a climatic chamber is a commonly used method of ensuring the accuracy of temperature measurements. This paper presents an experimental study aimed at evaluating the effects of chamber ventilation on the uncertainty of air temperature thermometers. Three types of sensors were used with a nominal resistance of 100 Ω, and with different thicknesses of 0.5 mm, 3 mm and 6 mm; the stability of each thermometer was measured at six temperatures ranging from − 40 ℃ to 60 ℃. The temperature stability of the thermometer improved significantly below 0 ℃ when a ventilation cap was applied to control the ventilation speed to a lower level inside the cap. This effect was dramatic with smallest diameter of thermometer, which showed fastest response behavior. The expanded uncertainty without a ventilation cap for the D0.5 sample at − 40 ℃ was 1.08 ℃, and decreased to approximately 0.24 ℃ with a ventilation cap. Air ventilation had no distinct effects on the temperature stability above 20 ℃ due to the enhanced control accuracy of the chamber. In conclusion, measurement uncertainty could be considerably reduced by appropriate control of the air circulation in the chamber, even under conditions of poor temperature stability in the chamber.