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In this work, the authors exploited the whispering gallery mode (WGM) resonator properties as a thermometer. The sensor is made of a cylindrical sapphire microwave resonator in the center of a gold-plated copper cavity. Two coaxial cables act as antennas and excite the WGM standing waves in the cylindrical sapphire at selected resonance frequencies in the microwave range. The system affords a high quality factor that enables temperature measurements with a resolution better than 15 µK and a measurement standard uncertainty of 1.2 mK, a value approximately three times better than that achieved in previous works. The developed sensor could be a promising alternative to platinum resistance thermometers, both as a transfer standard in industrial applications and as an interpolating instrument for the dissemination of the kelvin.

The study describes significant outcomes of the Metrology for Meteorology' project, MeteoMet, which is an attempt to bridge the meteorological and metrological communities. The concept of traceability, an idea used in both fields but with a subtle difference in meaning, is at the heart of the project. For meteorology, a traceable measurement is the one that can be traced back to a particular instrument, time and location. From a metrological perspective, traceability further implies that the measurement can be traced back to a primary realization of the quantity being measured in terms of the base units of the International System of Units, the SI. These two perspectives reflect long-standing differences in culture and practice and this project - and this study - represents only the first step towards better communication between the two communities. The 3 year MeteoMet project was funded by the European Metrology Research Program (EMRP) and involved 18 European National Metrological Institutes, 3 universities and 35 collaborating stakeholders including national meteorology organizations, research institutes, universities, associations and instrument companies. The project brought a metrological perspective to several long-standing measurement problems in meteorology and climatology, varying from conventional ground-based measurements to those made in the upper atmosphere. It included development and testing of novel instrumentation as well as improved calibration procedures and facilities, instrument intercomparison under realistic conditions and best practice dissemination. Additionally, the validation of historical temperature data series with respect to measurement uncertainties and a methodology for recalculation of the values were included.

Humidity is among the most important measured parameters related to HVAC applications, the storage of food products, industrial and medical gases, textile, paper and many other products requiring humidity measurement and control within certain limits. Humidity measurement techniques are diverse and each presents different challenges for use and calibration for a range of pressures and gases. Over the past few years, the development of humidity sensors and apparatus has matured to a level where traceable calibration is beneficial to all industries in which humidity and moisture measurement and control are important.

Cost, size, speed, and measurement range limitations make the resistance bridge not always suitable for temperature measurements with platinum resistance thermometers (PRTs) in industrial applications. However, high-accuracy resistance thermometer systems are often needed in many industrial applications, where measurement performances comparable to resistance bridges are often needed at a lower cost and size. A tiny, portable, ratiometric front-end exploiting a 24-bit analog-to-digital converter (ADC) with Σ Δ modulator is described. It was designed to measure the resistance ratio between a 100 Ω industrial PRT (IPRT) and a reference resistor with repeatability to within a few parts in 106. Its small size makes it ideal for integration in the stem-handle assembly of a thermometric probe, enabling an early transmission of measurement data in digital form. The ADC-based system design, development, and performance testing are discussed. The system was investigated in the resistance ratio range from about 4 × 10−3 to 5 × 10−2. Furthermore, a comparison between the system performance and a commercial AC resistance bridge was carried out and the results reported in this paper. An accurate thermometer for industrial applications resulted from the above developments. The compactness of the devices enabled an implementation of the ‘smart sensor’ concept in the measurement chain, where the front-end electronics was placed inside the IPRT handle together with an integrated memory to hold device identification, calibration coefficients, and the associated uncertainty. All data are transmitted to the readout module and are available to the user at a 5 Hz update rate for further analysis.

In the scope of the project HUMEA – Expansion of European research capabilities in humidity measurement within the EURAMET EMPIR program, the modular chamber for calibration of relative humidity instruments was designed, manufactured and characterized. The modular chamber consists of arbitrary numbers of aluminum blocks each of which provides accommodation for the one relative humidity probe and also has the fittings for pressure and temperature probes as well as ports for gas sampling and/or supplying. The gas can be supplied from the dew/frost point generator or the larger climatic chamber. In the latter case, the airflow through the chamber can be enhanced by using an additional fan. The preliminary study was carried out to investigate the improvement in temperature uniformity using a new chamber in combination with two climatic chambers. The investigation results show significant improvement in temperature uniformity thus lowering the uncertainties of the calibration of relative humidity instruments.

Wireless sensors networks (WSNs) are constantly expanding their application field, from simple two-state measurements (e.g., on/off, proximity detection, etc.) to distributed many-parameter measurements. Commercial WSNs offer a wide range of functions and performance with sensors sometimes achieving accuracy comparable with desktop instrumentation.

Launched in 2011 within the European Metrology Research Programme (EMRP) of EURAMET, the joint research project ‘MeteoMet’—Metrology for Meteorology—is the largest EMRP consortium; national metrology institutes, universities, meteorological and climate agencies, research institutes, collaborators and manufacturers are working together, developing new metrological techniques, as well as improving existing ones, for use in meteorological observations and climate records. The project focuses on humidity in the upper and surface atmosphere, air temperature, surface and deep-sea temperatures, soil moisture, salinity, permafrost temperature, precipitation, and the snow albedo effect on air temperature. All tasks are performed using a rigorous metrological approach and include the design and study of new sensors, new calibration facilities, the investigation of sensor characteristics, improved techniques for measurements of essential climate variables with uncertainty evaluation, traceability, laboratory proficiency and the inclusion of field influencing parameters, long-lasting measurements, and campaigns in remote and extreme areas. The vision for MeteoMet is to take a step further towards establishing full data comparability, coherency, consistency, and long-term continuity, through a comprehensive evaluation of the measurement uncertainties for the quantities involved in the global climate observing systems and the derived observations. The improvement in quality of essential climate variables records, through the inclusion of measurement uncertainty budgets, will also highlight possible strategies for the reduction of the uncertainty. This contribution presents selected highlights of the MeteoMet project and reviews the main ongoing activities, tasks and deliverables, with a view to its possible future evolution and extended impact.