Technical information

Fixed-point calibration per ITS-90
WIKA data sheet IN 00.38

Applications■ Industry (laboratory, workshop and production)

laboratory, D-K-15105-01-00

505.078231.928302.9146

29.7646

273.160.01

234.3155-38.8344■ Applicable to resistance thermometers

Description
An important element of quality is the traceability of themeasuring instruments used, in order to ensure thatthe measurement results are related to the national andinternational standard by means of an uninterrupted
measuring chain. The importance of the internationallyrecognised calibration certificate is thus increasingconstantly, since only such calibration results are comparableinternationally.
A minimal measurement uncertainty of down to ±2 mK canbe achieved with fixed-point calibration. Cells, in which thefixed points of high-purity materials (such as gallium or zinc)
can be realised, serve as temperature sources. During thephase transition, for example, from solid to liquid, the material
temperature remains constant at a constant pressure andcan therefore be used for the calibration.
With some materials, alongside the phase transitions,the triple points can also be used. At this point, the threeaggregate states of the respective material are in thermal
equilibrium. They can be prepared very precisely and are
repeatable at any time. Moreover, they can be maintained
over a longer period of time.

WIKA data sheet IN 00.38 ∙ 10/2017

Mercury Triple point■ High accuracy down to 2 mK

419.527

Water Triple point■ Traceable calibration in our DAkkS accredited calibration

692.677

Gallium Melting point

Special features

660.323

Tin Freezing point■ Calibration service companies and service industry

933.473

Zinc Freezing point■ Temperature sensor and transmitter manufacturers°C

Aluminium Freezing point■ Pharmaceutical industry

KITS-90 fixed points
Mercury to aluminium

The International Temperature Scale of 1990 (ITS-90)
defined 17 fixed points, from the triple point of hydrogen(-259.3467 °C) to the freezing point of copper (1,084.62 °C).
The WIKA laboratory, for example, calibrates at the triple
points of mercury and water, at the melting point of gallium
and also the freezing points of tin, zinc and aluminium. Thus,a temperature range from -38.8344 °C to 660.323 °C iscovered.
Not all temperature measuring instruments are suitable for
fixed-point calibration. With resistance thermometers, forexample, the platinum of the sensor must fulfil specific purity
criteria and its wire coiling must be free from stress.

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Typical calibration ranges for calibration in accordance with the internationaltemperature scale (ITS-90) in our DAkkS accredited calibration laboratory,
D-K-15105-01-00
Material
Mercury

Water

Gallium

Tin

ZincAluminium1)

TypeTemperature °C

Smallest measurement uncertainty that can be quoted 1)

Triple point-38.8344

3 mK

Triple point

0.01

2 mK

Melting point

29.7646

2.5 mK

Freezing point

231.928

5 mK

Freezing point

419.527

5 mK

Freezing point

660.323

10 mKBest case, if all conditions are met by the resistance thermometer to be tested

Scope of delivery

Accessories■ Calibration at the set points■ Temperature probe model CTP5000■ Additional testing of the thermometer: Stabilisation,

determination of the suitability of the thermometer byrepresentation of the ITS-90, determination of the part ofself-heatingOption■ Calculation of the deviation function with ITS-90■ Calculation of the deviation function as a polynomial

Page 2 of 2

WIKA data sheet IN 00.38 ∙ 10/2017

WIKA Alexander Wiegand SE & Co. KG
Alexander-Wiegand-Straße 30
63911 Klingenberg/GermanyTel.
+49 9372 132-0
info@wika.com
www.wika.com

10/2017 EN© 10/2017 WIKA Alexander Wiegand SE & Co. KG, all rights reserved.
The specifications given in this document represent the state of engineering at the time of publishing.
We reserve the right to make modifications to the specifications and materials.