Thermometry is the art of measuring temperature, a daily concept. Today, temperature measurements also touch other areas, such as humidity and the field of thermophysical quantities.

Fundamental metrology is carried out to support a wide range of applications, some of which are listed below. Measurements and comparisons to establish the degrees of equivalence between different institutes around the world are essential in order to provide a robust and coherent basis for calibration services world-wide.

• Temperature measurements may span a large range, from ultra-cold temperatures of –273 °C up to temperatures of several thousands of °C. A precise and accurate knowledge of temperature is important in science, technology and industry where precision and pushed limits are targeted.
  
  Primary thermometry, including precise instrumentation and standards, the establishment of an internationally common temperature scale and its realization, represent an important basis for all applications, and for science and innovation.
  
  However, the user is normally facing applications of secondary thermometry when determining temperature where all kinds of instruments may be found depending on the application: digital thermometers, thermo couples, temperature sensitive films, cameras, resistance thermometers, thermometers containing alcohol or mercury (the latter successively abandoned for environmental reasons)... This area is usually less precise, but also subject to larger measurement errors.
  
  Hence, temperature measurements are important for a vast range of areas and applications in industry (metallurgy, chemistry and biochemistry, quantum computing), the health sector (e.g. medical ablation techniques in human tissue by thermal heating) and environment (by monitoring and prevision of climate and climate changes in air, soil and water).


• Humidity may be expressed using several definitions; the most commonly met is "relative humidity". It has particular impact in industry (corrosion, food and drug industry, gas industry) and in measurements of climate prognostics and changes.


• Thermophysical quantities regroup a cross-disciplinary field where temperature is of primary interest. For example, the capacity of a material to store heat or to conduct electricity depends on its temperature. One thermophysical quantity of particular interest is the thermal conductivity of materials (thermal insulation of buildings and devices and power electronics). Others are linked to combustion, thermal radiation and heat loss.