Xylem sap flow measurement is a key method to quantify plant water use and assess the responses to environmental conditions and climatic change. However, available methods are generally invasive and of limited portability. This paper presents a non-invasive approach called TIMFLOW that combines microwave heat pulse and infrared thermography, while having a high portability and versatility potential. The methodology was tested in laboratory conditions for black poplar (Populus nigra) stems of various diameters (10–45 mm) and for the known sap flow velocity range (10–100 cm h−1). The heat pulse was generated by microwaves with a power amplifier supplying a bi-quad antenna at 2.45 GHz frequency located near the stem. The scene was filmed using a relatively low-cost light and compact InfraRed (IR) thermography camera. A stem temperature map was used to determine the heat pulse propagation velocity. The calculated heat velocity was highly correlated with the applied flow velocity with a unique relationship regardless of the diameter. The latter result confirms the equation of Marshall (1958) which links the sap velocity to the heat velocity with a vessel fraction of around 25 % within samples. The feasibility of outdoor measurements was also successfully tested. The assumed potentials and limitations of the proposed methodology are discussed. In summary, the study demonstrates the concept and validates, in woody stems, this new methodology for non-invasive portable sap flow velocity measurement.

Cet article présente une maquette pédagogique analogique polyvalente permettant l’observation, la compréhension et la mise en œuvre de boucles de régulation pour l’électronique de puissance et la commande de machine à courant continu. Cette maquette est utilisée en Travaux Pratiques mais aussi en projet pour les Master EEA première et deuxième année, principalement dans le parcours Energie Electrique, Environnement et Fiabilité des systèmes (3EFS) du département EEA de l’Université de Montpellier. L’objectif pédagogique est la compréhension des systèmes régulés ou asservis en manipulant une maquette où les correcteurs peuvent être réglés avec des composants sur supports. L’utilisation de l’oscilloscope, l’étude des chaînes instrumentales (capteur plus filtre), l’étude statique et dynamique d’un convertisseur en électronique de puissance sont des manipulations très constructives pour les étudiants. Nous présenterons ici comme application de cette carte analogique l‘étude de la régulation d’une machine à courant continu à aimant.

This work explores a contactless resistivity measurement method dedicated to the study of quantum phenomena. The method belongs to the category of RadioFrequency (RF) eddy currents and is based on a gradiometric inductive coil.

This paper describes the design and performance of the search coil magnetometers (SCM), which are part of the Plasma Wave Investigation (PWI) instrument onboard the BepiColombo/Mio spacecraft (Mercury Magnetospheric Orbiter), which will measure the electric field, plasma waves and radio waves for the first time in Mercury’s plasma environment. The SCM consists of two low-frequency orthogonal search coil sensors (LF-SC) measuring two components of the magnetic field (0.1 Hz – 20 kHz) in the spacecraft spin plane, and a dual-band search coil sensor (DB-SC) picking up the third component along the spin axis at both low-frequencies (LF: 0.1 Hz – 20 kHz) and high-frequencies (HF: 10 kHz – 640 kHz). The DB-SC and the two LF-SC sensors form a tri-axial configuration at the tip of a 4.6-m coilable mast (MAST-SC) extending from the spacecraft body, to minimize artificial magnetic field contamination emitted by the spacecraft electronics. After the successful launch of the spacecraft on 20 October 2018, an initial function check for the SCM was conducted. The nominal function and performance of the sensors and preamplifiers were confirmed, even with the MAST-SC being retracted and stowed in the spacecraft body, resulting in the detection of large interference signals likely from spacecraft electronics. The MAST-SC is scheduled for deployment after the Mercury orbit insertion of Mio in 2025, allowing the SCM to make the first higher frequency measurements of magnetic fluctuations in the Hermean magnetosphere and exosphere, and the local solar wind. These measurements will contribute to the investigation of fundamental problems in the Hermean plasma environment, including turbulence, magnetic reconnection, wave-particle interactions and particle acceleration.