DAkkS Calibration of Standard Thermometers (SPRT) 

The DAkkS calibration of ITS-90 standard thermometers (SPRT) is done at ITS-90 fixed points. 

Full range DAkkS calibration from argon triple point to silver freezing point
Use of state-of-the-art temperature fixed points
Triple set of temperature fixed points available
Turnaround time is five working days
Temperature probes can be calibrated from a length of 300 mm

Accredited calibration according to DIN EN ISO/IEC 17025 (DAkkS) of SPRTs at temperature fixed points (SPRT, Pt 25, Pt 2.5, Pt 0.25)

The accredited calibration according to DIN EN ISO/IEC 17025 (DAkkS) of ITS-90 Standard Platinum Resistance Thermometers (SPRT) is performed at ITS-90 fixed points.

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Accredited calibration according to DIN EN ISO/IEC 17025 (DAkkS) of a Standard Platinum Resistance Thermometer (SPRT) (WGa = 1.11807 or WHg = 0.844235) at the fixed points (freezing points, melting points, and triple points) of the ITS-90. Achievable DAkkS measurement uncertainties, including the ITS-90 deviation function (k=2):

Temperature Fixed Pointin °CMeasurement Uncertainty
Argon Triple Point-189.3442 °C5.5 mK
Mercury Triple Point-38.8344 °C3.5 mK
Water Triple Point0.01 °C2.5 mK
Gallium Melting Point29.7646 °C2.5 mK
Indium Freezing Point156.5985 °C5.5 mK
Tin Freezing Point231.928 °C4.5 mK
Zinc Freezing Point419.527 °C4.5 mK
Aluminum Freezing Point660.323 °C7.0 mK
Silver Freezing Point961.78 °C12 mK

The fixed points are selected based on the temperature ranges of the ITS-90. The temperature ranges of the ITS-90 are as follows:

Prior to calibration, the Standard Platinum Resistance Thermometer (SPRT) is sufficiently aged. Hydrostatic pressure effects occurring in the fixed-point cells are corrected. The self-heating of the Standard Platinum Resistance Thermometer (SPRT) is examined before the start of the calibration and taken into account in the calibration results. The calibration results include the resistance and W-values of the Standard Platinum Resistance Thermometer (SPRT), as well as two calibration curves (coefficients) calculated according to ITS-90 (with measurement currents of 0 mA and 1 mA unless otherwise specified).

The calibration in the range from Argon (-189 °C) to the Water Triple Point (0.01 °C) additionally includes the specification of a measurement uncertainty for extrapolation in accordance with EURAMET TG 01:2017 (up to the Nitrogen Boiling Point, ~196 °C) with a measurement uncertainty of 7 mK (k=2).

The minimum immersion depth of the Standard Platinum Resistance Thermometer (SPRT) is:

at -189 °C: 400 mm

at 962 °C: 450 mm 

in range -38 °C bis 660 °C: 300 mm

The maximum outer diameter is 8 mm.

Calibration duration: approximately 5-7 working days or as agreed.

Uncertainty of measurement during DAkkS calibration

Temperature rangeProcedureUncertainty of measurement
-196 °C to -189,3442 °CEURAMENT TG 01:20177,0 mK *
-189,3442 °CG-ITS-90, Part 2.3:2021 Argon triple point4,0 mK
-38,8344 °CG-ITS-90, Part 2.4:2021 Mercury triple point2,5 mK
0,01 °CG-ITS-90, Part 2.2:2018 Water triple point1,5 mK
29,7646 °CG-ITS-90, Part 2.4:2021 Gallium melting point2,0 mK
156,5985 °CKA16-10-02:2020-01 Indium melting point4,5 mK
231,928 °CG-ITS-90, Part 2.4:2021 Tin freezing point3,0 mK
231,928 °CKA16-10-05:2022-08 Tin melting point6,0 mK
419,527 °CG-ITS-90, Part 2.4:2021 Zinc freezing point3,0 mK
419,527 °CKA16-10-05:2022-08 Zinc melting point10 mK
660,323 °CG-ITS-90, Part 2.4:2021 Aluminium freezing point5,0 mK
660,323 °CKA16-10-05:2022-08 Aluminium melting point18 mK
961,78 °CG-ITS-90, Part 2.4:2021 Silver freezing point10 mK
Calibration at temperature fixed points.
* Extrapolation
Temperature rangeProcedureUncertainty of measurement
-189,3442 °C to 0,01 °CG-ITS-90, Part 5:2021 fixed points: Ar, Hg, TPW5,5 mK
-38,8344 °C to 29,7646 °CG-ITS-90, Part5:2021 fixed points: Hg, TPW, Ga3,5 mK
0 °C to 29,7646 °CG-ITS-90, Part5:2021 fixed points: TPW, Ga2,5 mK
0 °C to 156,5985 °CKA16-10-05:2022-08 fixed points: TPW, In
melting points
5,5 mK
0 °C to 231,928 °CKA16-10-05:2022-08 fixed points: TPW, In, Sn melting points7,0 mK
0 °C to 419,527 °CG-ITS-90, Part5:2021 fixed points: TPW, Sn, Zn4,5 mK
0 °C to 419,527 °CKA16-10-05:2022-08 fixed points: TPW, Sn, Zn melting points12 mK
0 °C to 660,323 °CG-ITS-90, Part5:2021 fixed points: TPW, Sn, Zn, Al7,0 mK
0 °C to 660,323 °CKA16-10-05:2022-08 fixed points: TPW, Sn, Zn, Al melting points20 mK
0 °C bis 961,78 °CG-ITS-90, Part5:2021 fixed points: TPW, Sn, Zn, Al, Ag12 mK
Calibration at temperature fixed points with characteristic curve determination according to ITS-90. The measurement uncertainty refers to the characteristic curve in the specified range.

Calibration at temperature fixed points

Klasmeier’s calibration service calibrates standard thermometers (SPRT) by using ITS-90 temperature fixed points. Depending on the customer’s requirements, slim temperature fixed points with greater measurement uncertainties and primary “large” ITS-90 temperature fixed points in heat pipes or ISO towers with excellent measurement uncertainties can be used. The order of the fixed points at which calibration is performed results in falling temperatures for SPRT’s. To exclude thermometer drift, the water triple point is measured after each fixed point measurement and thus the drift of the temperature probe is controlled. In addition, each resistance thermometer is annealed at the highest operating temperature before calibration and the annealing drift is determined with the use of the water triple point. Self-heating errors and hydrostatic pressure effects are analysed and taken into account during calibration. The DAkkS calibration certificate is internationally accepted and can also be used abroad.

Short immersion depth from 300mm

By using slim and large temperature fixed points, as well as the modern ISO towers, standard thermometers of the ITS-90 (SPRTs as Pt100 or Pt25) can be calibrated from an immersion depth of 300mm with excellent measurement uncertainties.

New digital archive Klasmeier Cloud:
Calibration documents quickly and easily available

The new Klasmeier Cloud – the perfect archive for all calibration documents. From now on, our customers will find a QR code on all devices calibrated by Klasmeier, with which they can quickly and easily access our digital archive.

Especially useful: In addition to all calibration documents, the contact details of the relevant contact person at Klasmeier are also always available there. So even five or more years from now, if you have any questions about your calibration product, you can find the information you need with just one click.

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