2015 年 81 巻 832 号 p. 15-00307
Japan Agency for Marine-earth Science and Technology (JAMSTEC) has been developing a 300 L class constant temperature bath to calibrate temperature sensors monitoring ocean water temperatures. This system consists of a constant temperature bath which requires the temperature stability within ±1 mK. The purpose of this study is to investigate experimentally the performance and accuracy of the 300 L class constant temperature bath. To evaluate the temperature distribution within the bath, we first evaluated the measurement uncertainty of a 12 channel thermometer to ensure the meaningful results with temperature differences at 1 mK level. Results using this 12 channel thermometer and another reference thermometer indicated that although temperature stability of the 300 L class constant temperature bath was within ±1 mK at each measuring point, the total calibration time was longer than the targeted time. In order to elucidate the reason for this, the transient temperature distribution was measured with the 12 channel thermometer, and it was found that a region within the bath takes a longer time to reach stability. Moreover, measurement of the velocity distribution within the bath using Particle Image Velocimetry showed that a lack of turbulent flow in the bath caused this delay.