Studies on the behavior of water triple-point cells

Several triple point of water (TPW) cells from four different manufacturers were investigated in the same TPW maintenance bath with three standard platinum resistance thermometers. Temperature differences between the water triple point among cells were analyzed and found to be within 0.319 mK and repeatability to 0.015 mK over four to five months. The variations of temperature with height in different cells were compared with each other and also with the expected value of -7.3x10(-4) K(.)m(-1). The effect of the depth of immersion of the TPW cell in the maintenance bath on the water triple-point was studied and discussed here.