Method for compensating heat flux errors in mini-TPW cell measurements

Martti Heinonen (Corresponding Author), E. Isosaari

Research output: Contribution to journalArticleScientificpeer-review


Small triple-point-of-water cells (mini-TPW) are used in laboratories to monitor the stability of PRTs. Compared with a standard TPW cell, heat flow in the thermometer well usually disturbs the apparent equilibrium temperature to a larger extent in a mini-TPW cell due to its smaller dimensions. In this paper, the heat flow effect is studied on the basis of experimental data. Special attention is paid to the thermal conduction along a thin thermometer probe and to the self-heating of the probe. A new method for compensating the error due to the heat flow is presented. It is shown that the compensated results are in good agreement with results obtained with standard TPW cells. The determined differences were well within the estimated expanded uncertainty of 2 mK (k = 2). The heat flow effect was studied experimentally by controlling the temperature of the upper part of a PRT inserted in a mini-TPW cell. Also, the effect of different fillings of the measurement well of the cell was studied. Without the compensation, thin metal-sheathed PRTs (1.6 and 2.2 mm) indicated 3 to 9 mK differences between mini-TPW and standard TPW cells.
Original languageEnglish
Pages (from-to)836-843
JournalInternational Journal of Thermophysics
Issue number3
Publication statusPublished - 2008
MoE publication typeA1 Journal article-refereed


  • Mini-TPW
  • Thermal conduction
  • Triple point of water

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