Physical measurements

The latest publications in this offer are:

• December 10, 2025

  R3050

  Measurements in meteorology

  Meteorological measurements aim to quantify the different quantities that characterize the physical and thermodynamic state of the atmosphere, such as wind, temperature, humidity, solar radiation. Meteorological measurements can have various purposes, which condition the exposure of the sensors, a major factor for their representativeness.This article focuses on detailing each of these quantities (definitions, types of measurements carried out, influencing factors and exposure rules), mainly for in-situ measurements.

• September 10, 2025

  R2765

  Thermoelectric microwaves

  Technical developments, and in particular the miniaturization of sensors, have given rise to a new family of thermocouples: thermoelectric microprobes.This article provides an overview of these increasingly widespread measuring instruments, by presenting the different types of microthermocouples available, their manufacturing, their operating modes (with or without contact) and their characteristics. Specific calibration methods and sources of error for these new thermocouples are also discussed.

• September 10, 2025

  R3049

  Relative humidity measurement in climatic environments

  To make the right choice of instruments, for measuring relative humidity is not easy, given the various technical specifications announced by hygrometer manufacturers, with an accuracy of around ±1% RH.This article presents the hygrometric parameters used to calculate relative humidity values, ​​from a temperature measurement and an associated hygrometric parameter, with the relationships between the different parameters.It presents the three main types of hygrometers (impedance variation, condensation, psychrometer) used for measuring or determining relative humidity, in climatic environments, and gives examples of calculation of uncertainty, in relative humidity, from measurements with a psychrometer and a condensation hygrometer, combined with a thermometer.

• July 10, 2025

  R2385

  Solid-state gas sensor technology

  Gas microsensors are of great industrial interest due to their small size, low consumption, low cost and therefore deployable in a distributed network. Semiconductor gas sensors, although having limited performance compared to analyzers, are among the most commercialized sensors along with electrochemical and optical sensors.This article covers the operation of these sensors, the main materials used (metal oxides) with their detection mechanism as well as the design, manufacturing, characterization and calibration techniques. Current avenues of research around electronic noses and associated perspectives are also discussed.

• June 10, 2025

  R2380

  Gas detectors

  Gas detectors, whether they are called explosimeters, toximeters or oxygenometers, are mainly used to monitor the atmosphere. They are designed to trigger an alarm following a measurement when the atmosphere becomes dangerous (explosible, toxic, lack or excess of oxygen).This article begins by defining the concepts associated with these devices, in particular the danger thresholds. It then presents the principles of detection, their characteristics and influencing factors, and the choice criteria of the various devices.

• November 10, 2024

  R2050

  Vacuum measurement

  Vacuum is the term to describe the state of a gas which pressure or density is lower than that of the prevailing atmospheric pressure. The defined range that can thus be measured, providing that the traceability to the SI exists, is widely extended since it covers fourteen orders of magnitude.This article deals with reference methods used to establish the traceability to pressure standards and with the variety of instruments which allow to perform measurements from rough to ultra-high vacuum.

• October 10, 2024

  R2220

  Differential pressure flowmeters

  This article deals with the measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full.The principle of measurement consists in creating a local restriction in the fluid flow within a pressurised flow, which generates a pressure difference within the fluid which is related to the mass flow. There are as many flowmeters based on this principle as there are mechanically possible implementations of this local restriction.The best known are diaphragms or orifice plates, venturis and nozzles. The strength of this measurement technology lies in the fact that it benefits from extensive international standardization documents and exhaustive feedbacks.

• January 10, 2024

  R2164

  Imaging techniques for fluid mechanics measurement

  Imaging is a technique used in various fields related to fluid mechanics. It allows the measurement of geometric parameters such as size and shape, as well as scalar field variables like temperature, pH, and mixture.This article provides an overview digital imaging and its application in fluid mechanics. It presents the main experimental setups used and their implementation. The aspects of signal processing and information management, crucial in this context, are also addressed. Finally, the article illustrates the potential of the technique through several examples of applications emphasizing coupling and ultra-fast imaging.

• January 10, 2024

  R2935

  Albedo measurement

  Albedo, also known as solar reflectivity, is a measure of a surface's ability to reflect sunlight. The albedo of a surface also determines the amount of heat reflected by that surface. It is an essential parameter for understanding the thermal balance of a surface exposed to solar radiation, in the field of thermal comfort, climatology and spacecraft.The albedo of a surface can be measured in situ or in the laboratory. In the laboratory, the most commonly used method is spectral. On site, the sun's natural rays are generally used to measure the incident and reflected flux using a pyranometer. In all cases, there are commercial devices for measuring albedo.This article does not cover the albedo of planets or albedo in astronomy.

• May 10, 2023

  R2770

  Scanning thermal microscopy (SThM)

  This article presents a set of scanning thermal microscopy (SThM) techniques dedicated to the thermal imaging of surfaces as well as the analysis of surface temperature, material thermophysical properties and heat transfer physical mechanisms at micro and nanoscales. It focuses on one of them: the SThM using resistive probes.The technique is described in detail: its instrumentation and its different operating modes, the parameters influencing the measurement as well as the strategies proposed to carry out localized thermal measurements, including the current calibration methodologies applied to resistive probes.Advices of good practice are given throughout the article, which also gives the main challenges and limitations of the SThM technique and the current trends for its development.

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