Standard Guide for Use of Water Triple Point Cells

Importancia y uso:

4.1 This guide describes a procedure for placing a water triple-point cell in service and for using it as a reference temperature in thermometer calibration.

4.2 The reference temperature attained is that of a fundamental state of pure water, the equilibrium between coexisting solid, liquid, and vapor phases.

4.3 The cell is subject to qualification but not to calibration. The cell may be qualified as capable of representing the fundamental state (see 4.2) by comparison with a bank of similar qualified cells of known history, and it may be so qualified and the qualification documented by its manufacturer.

4.4 The temperature to be attributed to a qualified water triple-point cell is exactly 273.16 K on the ITS-90, unless corrected for isotopic composition (refer to Appendix X3).

4.5 Continued accuracy of a qualified cell depends upon sustained physical integrity. This may be verified by techniques described in Section 6.

4.6 The commercially available triple point of water cells described in this standard are capable of achieving an expanded uncertainty (k=2) of between ±0.1 mK and ±0.05 mK, depending upon the method of preparation. Specified measurement procedures shall be followed to achieve these levels of uncertainty.

4.7 Commercially-available triple point of water cells of unknown isotopic composition should be capable of achieving an expanded uncertainty (k=2) of no greater than 0.25 mK, depending upon the actual isotopic composition (3). These types of cells are acceptable for use at this larger value of uncertainty.

Subcomité:

E20.07

Referida por:

D6466-10R18, D2162-21, D0445-24, E0644-11R19, D2532-22, E2593-17R23, D0445-24, E0344-23, D8278-20, E2730-22, D8164-21, D0445-24, D7279-20, D7279-20, E0879-20, D7279-20

Volúmen:

14.03

Número ICS:

17.200.20 (Temperature-measuring instruments)

Palabras clave:

calibration; defining fixed point; fixed point; hydrostatic head pressure; International Temperature Scale of 1990 (ITS-90); intrinsic property; Kelvin Thermodynamic Temperature Scale (KTTS); qualification; self-heating; standard platinum resistance thermometer (SPRT); triple point; triple point of water; water triple point cell ;