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The title of the thesis: Enhancing metrological traceability for pressure and multi-quantity measurements - A unified approach for static, dynamic, and digital calibration processes

Thesis defender: Sari Saxholm
Opponent: Dr. Jiří TesaÅ™, ÄŒeský metrologický institut (CMI), Brno, Czech Republic
Custos: Prof. Erkki Ikonen, Aalto University School of Electrical Engineering

Reliable measurements are essential in science, industry, and regulation. They form the basis for safety, comparability, and technological development. As technologies evolve, systems monitored through measurements become more complex and increasingly include rapidly changing conditions and the simultaneous measurement of multiple interdependent quantities. The metrological traceability of measurement results must be enhanced to meet the requirements of today and the future.

Metrology refers to the science of measurement and its application. This dissertation examines how metrological traceability can be strengthened in challenging measurement scenarios. By developing calibration methods, measurement standards, and digital processes, a unified framework is established to meet increasingly diverse measurement needs. Traceability was investigated across four measurement scopes: pressure measurements, multi quantity measurements (simultaneous measurement of pressure, temperature, and humidity), dynamic pressure measurements, and reactive gas measurements (focus on oxidized mercury). In addition, the work examined digital traceability chains that are independent of the field in which they are used.

As a result of this work, the pressure unit was realized using the base units of the SI (International System of Units). For both the instruments used in multi‑quantity measurements and those used in dynamic pressure measurements, calibration systems were developed that enable metrologically traceable calibrations under real‑life conditions. The outcomes benefit, for example, climate research, industrial process control, engine diagnostics, and safety‑critical systems. For reactive gas measurements, the work resulted in the development of a calibration gas generator whose reliability was improved through a comprehensive measurement uncertainty analysis. These results can be used to enhance the accuracy of on-line emission monitoring. In addition, the work enhanced the traceability of digital calibration chains by examining the digitalization of traceability documentation, mainly calibration certificates. The results contribute to achieving the broader goal; improved data usability enables its integration into quality systems and automated workflows.

The developments carried out in this dissertation strengthen metrological traceability across multiple fields of measurements and enhance the reliability and comparability of measurements and measurement results.

Key words: traceability, reliability, calibration, measurement, metrology

Thesis available for public display 7 days prior to the defence at .

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