DAkkS (17025) calibration SPRT at temperature fixed points
(SPRT, Pt 25, Pt 2,5, Pt 0,25)

The DAkkS (17025) calibration of an ITS-90 standard thermometer is done at ITS-90 temperature fixed points.

SKU: 1403, 1412, 1428/1429, 1428, 1431, Category: Tags: , , , , ,


DAkkS (17025) calibration of a standard thermometer (WGa ≥ 1,11807 or WHg ≤ 0,844235) at the temperature fixed points (freezing points, melting points & triple points) of the ITS-90.

Achievable DAkkS (17025) measurement uncertainties including ITS-90 deviation function (k=2):

Temperature fixed points in °C Measurement uncertainties
Argon triple point -189,3442 °C 5 mK
Mercury triple point -38,8344 °C 3,5 mK
Water triple point 0,01 °C 2,5 mK
Gallium melting point 29,7646 °C 2,5 mK
Indium freezing point 156,5985 °C 5,5 mK
Tin freezing point 231,928 °C 3,0 mK
Zinc freezing point 419,527 °C 3,0 mK
Aluminium freezing point 660,323 °C 5,0 mK
Silver freezing point 961,78 °C 10 mK

The temperature fixed points are selected according to the temperature ranges of the ITS-90. You can see the temperature ranges of the ITS-90 here:

Before calibration, the standard thermometer is annealed. Hydrostatic pressure effects that occur in the temperature fixed point cells are corrected. The self-heating of the standard thermometer is investigated before the start of calibration and taken into account when calculating the calibration results. The resistance and W values of the standard thermometer are given as calibration results, and two characteristic curves (coefficients) are calculated according to the ITS-90 (with measuring current 0mA and 1mA, unless otherwise specified).

Calibration in the range argon (-189 °C) to the water triple point (0.01 °C) additionally includes the specification of a measurement uncertainty for extrapolation according to EURAMET TG 01:2017 (to the nitrogen boiling point ,~196 °C) with a measurement uncertainty of 7 mK (k=2).

The minimum immersion depth of the standard thermometer is at -189 °C: 400 mm, in the range -38 °C to 660 °C: 300 mm and at 962 °C: 450 mm. The maximum outer diameter is 8 mm.

Calibration time approx. 5-7 working days or by arrangement.


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