Precise Thermometer Calibration for the Highest Demands
Rely on our DAkkS-accredited calibration according to DIN EN ISO/IEC 17025 for your Standard Platinum Resistance Thermometers (SPRT).
We can calibrate your SPRTs across the entire temperature range of the ITS-90, ensuring maximum accuracy and traceability to international standards.
Our Services
Accredited calibration of SPRTs (length ≥ 300 mm)
Temperature range: -196 °C to +961 °C – full coverage of ITS-90
Calibration method: Fixed-point calibration at ITS-90 fixed points
Selectable calibration accuracy – from melting point to high-end freezing point calibration
Proficiency testing according to DIN EN ISO/IEC 17043
Repair service for SPRTs in our own workshop
Your Advantages at a Glance
Full Flexibility in Accuracy
The choice is yours:
Calibration at melting points
(economical, cost-effective, higher
measurement uncertainty)
Calibration at freezing points
(extremely low measurement uncertainty for the highest demands)
Short Turnaround Times of 5 Business Days
→ Minimize downtime – your standard thermometers are quickly back in use.
Minimal Measurement Uncertainties
→ Benefit from maximum precision:
We get the best out of your thermometer.
Everything from a Single Source
→ Complete package from calibration and proficiency testing to repair – all at Klasmeier.
Central Location in Fulda
→ Perfect accessibility – drop off your SPRT in person or use our secure courier service.
Paperless Documentation
→ Accessible at any time, legally signed.
Full transparency and security via our modern cloud solution.
Details about Our Calibration Service for SPRT Standard Thermometers
Why Individual Calibrations for SPRTs?
A Standard Platinum Resistance Thermometer (SPRT) is the most precise measuring instrument for representing the International Temperature Scale (ITS-90). To ensure your SPRT reaches its full potential, it must be calibrated exactly and individually at the defining fixed points. This provides you with reliable measurement results, fulfills standard requirements, and avoids costly wrong decisions.
Our Range of Services at a Glance
| Service | Temperature Range | Method | Typical Expanded Measurement Uncertainty* |
| Full Range Calibration | –189 °C … 660 °C | Melting or freezing points | up to 3 mK |
| Partial Range Calibrations | Freely selectable segments of the ITS-90, e.g., 0 °C … 419 °C | Melting or freezing points | 2 – 6 mK |
| Extension Modules | Additional fixed points if the ITS-90 range does not fit perfectly. (Argon, Mercury, Gallium, Indium) | same as basic calibration | 2 – 10 mK |
*all specifications for k = 2 (≈ 95% confidence level)
Two Proven Methods – Melting vs. Freezing Points
| Method | Typical Measurement Uncertainties* | Cost Factor** | Advantages | Typical Turnaround |
| Melting Point Calibration (developed by Klasmeier & accredited) | Ar 10 mK Hg 3.5 mK WTP 2.5 mK Ga 2.5 mK Sn 7 mK Zn 12 mK Al 20 mK | ≈ 50% of the cost of a freezing point calibration | • Fast turnaround • Economical solution • Measurement uncertainties are sufficient for many applications • Ideal for reference thermometers as standards in comparison method calibrations | approx. 5 business days |
| Freezing Point Calibration (most precise ITS-90 representation) | Ar 4 mK Hg 2.5 mK WTP 1.5 mK Ga 2 mK Sn 3 mK Zn 3 mK Al 5 mK | Reference | • Highest precision • Ideal for primary standards | approx. 7 business days |
* k = 2, including ITS-90 deviation function (if specified).
For measurement uncertainties, see the graphic below.
** Exemplary comparison based on our full-range packages (KK-1413 vs. KK-1404). Depending on the partial range, the difference may vary slightly but is typically around 40–60%. All prices and measurement uncertainties are taken from our service catalog.
Conclusion: If maximum accuracy is required (e.g., for high-end primary standards), we unreservedly recommend freezing point calibration.
For less critical applications – such as reference thermometers for secondary calibrations – the melting point calibration developed by Klasmeier offers a significantly more cost-effective alternative while still providing excellent overall uncertainty.
Measurement Uncertainties and Article Numbers for SPRT Calibration at Klasmeier
| Art. No. | Temperature Range (°C) | Fixed Points* |
| KK-1404 | –189 … 660 °C | Ar 10 mK, Hg 3.5 mK, WTP 2.5 mK, Ga 2.5 mK, Sn 7 mK, Zn 12 mK, Al 20 mK |
| KK-1424 | –189 … 660 °C | Ar 4 mK, Hg 2.5 mK, WTP 1.5 mK, Ga 2.0 mK, Sn 3 mK, Zn 3 mK, Al 5 mK |
| KK-1402 | 0 … 660 °C | WTP 2.5 mK, Ga 2.5 mK, Sn 7 mK, Zn 12 mK, Al 20 mK |
| KK-1401 | 0 … 660 °C | WTP 1.5 mK, Ga 2.0 mK, Sn 3 mK, Zn 3 mK, Al 5 mK |
| KK-1411 | 0 … 419 °C | WTP 1.5 mK, Ga 2.0 mK, Sn 3 mK, Zn 3 mK |
| KK-1408 | 0 … 419 °C | WTP 2.5 mK, Ga 2.5 mK, Sn 7 mK, Zn 12 mK |
| KK-1409 | 0 … 230 °C | WTP 2.5 mK, Ga 2.5 mK, In 5.5 mK, Sn 7 mK |
| KK-1413 | 0 … 156 °C | WTP 1.5 mK, Ga 2.0 mK, In 4.5 mK |
| KK-1410 | 0 … 29 °C | WTP 1.5 mK, Ga 2.0 mK |
| KK-1405 | –189 … 29 °C | Ar 4 mK, Hg 2.5 mK, WTP 1.5 mK, Ga 2.0 mK |
| KK-1412 | –189 … 29 °C | Ar 10 mK, Hg 3.5 mK, WTP 2.5 mK, Ga 2.5 mK |
| KK-1400 | –38 … 29 °C | Hg 2.5 mK, WTP 1.5 mK, Ga 2.0 mK |
| KK-1406 | –38 … 29 °C | Measurement uncertainties on request |
* k = 2, for measurement uncertainties see graphic below.
The specified values apply directly at the respective fixed points. In the intermediate ranges, experience shows that uncertainties are 0.5 – 2 mK higher.
Scope of Services for SPRT Calibrations
A DAkkS-accredited calibration according to DIN EN ISO/IEC 17025 of a standard thermometer (WGa ≥ 1.11807, WHg ≤ 0.844235) at freezing, melting, and triple points of the ITS-90. Overview of the most important service elements:
Smallest measurement uncertainties at the fixed points (k = 2)
- Argon −189.3442 °C – 4.0 mK
- Mercury −38.8344 °C – 2.5 mK
- Water triple point 0.01 °C – 1.5 mK
- Gallium 29.7646 °C – 2.0 mK
- Tin 231.928 °C – 3.0 mK
- Zinc 419.527 °C – 3.0 mK
- Aluminum 660.323 °C – 5.0 mK
Measurement uncertainties also depend on the individual thermometer and the procedure. Please consider the respective specifications for measurement uncertainties.
Extrapolation to the nitrogen boiling point (-196 °C)
with 7 mK measurement uncertainty according to EURAMET TG 01:2017 for a calibration at the argon triple point.
ITS-90 deviation functions
included for each interval range; their uncertainties are only 0.5 – 2 mK above the fixed-point values.
Thermometer Pretreatment & Corrections
– Pre-aging (stabilization) of the SPRT
– Correction of hydrostatic pressure effects in the fixed-point cells
– Determination and consideration of self-heating
Scope of Delivery of the Calibration
– Resistance and W-values at each fixed point
– ITS-90 coefficients for 0 mA and 1 mA measuring current
– DAkkS-accredited calibration certificate with full measurement logging
Technical Requirements
For all SPRT calibrations, WGa ≥ 1.11807 or WHg ≤ 0.844235 must be met according to ITS-90. If this is not the case, please continue reading here: Calibration of Resistance Thermometers or contact us for further information. Your thermometer can be calibrated at temperature fixed points, but more cost-effectively with less effort.
| Valid for | Minimum Immersion Depth | Max. Outer Diameter |
| KK-1404, KK-1424, KK-1405, KK-1400, KK-1428, KK-1423, KK-1413 | 400 mm | 8 mm |
| KK-1401, KK-1402, KK-1408, KK-1409, KK-1410, KK-1411, KK-1412 | 300 mm | 8 mm |
All items not mentioned follow the same limits according to the offer text.
Optional Extension Modules (Additional Fixed Points)
Specifically expand an existing ITS-90 calibration with further fixed points. This is practical, for example, if you want to measure temperature in both the negative and positive ranges. This is not standardly considered in the ITS-90. Therefore, you can expand the standard ranges of the ITS-90 in the negative and positive ranges with us.
| Art. No. | Additional Fixed Points (approx. temp.) | Measurement Uncertainty* | Description |
| KK-1428 | Argon −189 °C Mercury −38 °C | 10 mK (Ar) 2.5 mK (Hg) | Additional fixed points (Ar, Hg) higher measurement uncertainty |
| KK-1423 | Argon −189 °C Mercury −38 °C | 4 mK (Ar) 2.5 mK (Hg) | Additional fixed points (Ar, Hg) optimal measurement uncertainty |
| KK-1425 | Gallium 29.8 °C | 2 mK (Ga) | Additional fixed point (Ga) |
| KK-1426 | Indium 156.6 °C | 4.5 mK (In) | Additional fixed point (In) |
| KK-1424 | Mercury −38 °C Gallium 29.8 °C | 2.5 mK (Hg) 2 mK (Ga) | Additional fixed points (Hg, Ga) |
* k = 2
All modules down to the argon triple point include an extrapolation to the nitrogen boiling point (−196 °C) according to EURAMET TG 01. The minimum immersion depth and max. outer diameter correspond to the basic calibrations (approx. 400 mm / 8 mm).
Calibration Prices – Overview
| Art. No. | Temperature Range | Method | Category | Price (EUR) |
| KK-1404 | –189 … 660 °C | Freezing Triple Points | Full Range | 3,430 € |
| KK-1413 | –189 … 660 °C | Melting Triple Points | Full Range | 2,730 € |
| KK-1402 | 0 … 660 °C | Freezing Triple Points | Partial Range | 2,655 € |
| KK-1412 | 0 … 660 °C | Melting Triple Points | Partial Range | 2,175 € |
| KK-1401 | 0 … 419 °C | Freezing Triple Points | Partial Range | 2,100 € |
| KK-1411 | 0 … 419 °C | Melting Triple Points | Partial Range | 1,790 € |
| KK-1410 | 0 … 230 °C | Melting Triple Points | Partial Range | 1,790 € |
| KK-1409 | 0 … 156 °C | Melting Triple Points | Partial Range | 1,610 € |
| KK-1408 | 0 … 29 °C | Melting Triple Points | Partial Range | 1,330 € |
| KK-1405 | –189 … 29 °C | Melting Triple Points | Partial Range | 2,235 € |
| KK-1400 | –189 … 29 °C | Melting Triple Points (higher accuracy) | Partial Range | 2,800 € |
| KK-1406 | –38 … 29 °C | Melting Triple Points | Partial Range | 1,680 € |
| KK-1428 | –189 °C + –38 °C | Additional Fixed Points (Ar, Hg) | Extension | 835 € |
| KK-1423 | –189 °C + –38 °C | Additional Fixed Points (Ar, Hg) | Extension | 975 € |
| KK-1425 | 29 °C | Additional fixed point (Ga) | Extension | 205 € |
| KK-1426 | 156 °C | Additional fixed point (In) | Extension | 320 € |
| KK-1424 | –38 °C + 29 °C | Additional Fixed Points (Hg, Ga) | Extension | 485 € |
All prices are net; shipping and insurance costs are not included.
All prices and uncertainties are for information purposes only and are taken from our service catalog.
New: Digitally Signed Calibration Certificates with Official Accreditation Symbol
Recently, we have started providing our calibration certificates with a digital accreditation symbol, which was officially introduced by the DAkkS (German Accreditation Body). This means your calibration records are legally digitally signed and bear a forgery-proof, recognized seal.
Your Advantages at a Glance
- Forgery-proof and verifiable
The signature can be checked electronically – thus excluding manipulation - Legally binding and internationally recognized
The digital symbol confirms the validity and authenticity of the calibration certificates – even without a paper printout. - Digitally available – anytime anywhere
You receive your calibration certificates as a PDF via our cloud solution, securely archived and accessible at any time. - Future-proof audit-compliant
Ideal for digital processes, ISO-compliant documentation, and quick access during audits.
Further information can be found directly at the DAkkS:
Digital Archive Klasmeier Cloud:
Calibration documents accessible quickly and easily
The Klasmeier Cloud – the perfect filing system for all calibration documents. On all devices calibrated by Klasmeier, you will find a QR code that takes you quickly and easily to our digital archive.
Particularly practical: In addition to all calibration documents, the contact details of the respective contact person at Klasmeier are always included. This way, even in five or more years, you can find the desired information with one click if you have questions about your calibration product.
Klasmeier – because precise temperature measurement is a matter of trust.
Your advantages in detail:
Individually scalable calibrations
→ With us, you determine how precise the calibration should be – and thus also the price.
In-house manufacturing service competence
→ We manufacture our own sensors and repair SPRTs professionally – no long distances, no third-party service providers.
All-round worry-free package
→ Calibration, proficiency testing, consulting, and documentation – with us, you are audit-ready and legally on the safe side.
Digital efficiency
→ Calibration data device information available online at any time – secure, convenient, GDPR-compliant.
Added Value for Audits Consulting
We can offer you support in audit preparation:
Accredited calibrations across the entire ITS-90 range
→ This makes you perfectly prepared for your next assessment.
Proficiency testing to confirm your measurement uncertainties
Practical tips and advice from an accredited laboratory
→ So that your temperature measurement technology convinces not only on paper but also in everyday use
Together, We’ll Find the Right Solution for You
Speak directly with our expert!
Your contact person for calibration services
and proficiency testing:
Boris Kalb
