Measuring EMF

3 Key excerpts on "Measuring EMF"

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  eBook - ePub

  Human Exposure to Electromagnetic Fields

  From Extremely Low Frequency (ELF) to Radiofrequency

  • Patrick Staebler(Author)
  • 2017(Publication Date)
  • Wiley-ISTE

    (Publisher)

  8.4. Measuring high-frequency electromagnetic fields

  8.4.1. General

  The physical quantities measured for quantifying high-frequency electromagnetic fields (100 kHz–300 GHz) are the electric field and the magnetic field. These quantities are related beyond a distance of a wavelength from the source [1.15] and make it possible to extract the power density from it [1.16] . The measuring device is chosen depending on the frequency domain to be analyzed, the characteristics of the radiation (reactive field, radiative field, etc.) and the number of radiation sources.

  The basic constituents of a measuring chain are as follows:

  • – the probe, formed from one or several sensors;
  • – coaxial cables, which transfer electric signals from the probes to the processing unit, if it is remote;
  • – the processing unit, which converts the signals into quantities that can be used to quantify exposure.

  Furthermore, broadband measurements are distinguished from narrowband measurements.

  8.4.2. Measuring sensors for electromagnetic fields

  The sensors used are radioelectric antennae, which deliver an electric power proportional to the received electric or magnetic field strength. The antenna factor, an essential element from the calibration certificate, makes it possible to directly associate a field value to it. An alternative basic technique consists of estimating the power through calorimetric measurement (bolometer). This power is then compared with the exposure limit converted into the same unit.

  Monopolar antennae are distinguished from dipole antennae. These antennae pick up the electric component (E

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  eBook - ePub

  Advanced Materials for Electromagnetic Shielding

  Fundamentals, Properties, and Applications

  • Maciej Jaroszewski, Sabu Thomas, Ajay V. Rane, Maciej Jaroszewski, Sabu Thomas, Ajay V. Rane(Authors)
  • 2018(Publication Date)
  • Wiley

    (Publisher)

  3 Electromagnetic Field Sensors

  Vishnu Priya Murali

  1*

  , Jickson Joseph

  2,3*

  , and Kostya (Ken) Ostrikov2,3

  1 Department of Biomedical Engineering, University of Memphis, Memphis, Tennessee, USA 2 School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland, 4000, Australia 3 CSIRO−QUT Joint Sustainable Processes and Devices Laboratory, Commonwealth Scientific and Industrial Research Organisation, P.O. Box 218, Lindfield, New South Wales, 2070, Australia

  Abbreviations

  AC

  Alternating current

  AM

  Amplitude modulation

  AMR

  Anisotropic magneto‐resistor

  DC

  Direct current

  EMF

  Electromagnetic field

  emf

  Electro‐motive force

  FM

  Frequency modulation

  GMR

  Giant magnetoresistance effect

  HTS

  High temperature SQUID

  LTS

  Low temperature SQUID

  MR

  Magneto‐resistor

  PM

  Phase modulation

  RCP

  Rogowski–Chattock potentiometer

  RF

  Radio frequency

  RMS

  Root mean square

  SA

  Specific absorption

  SAR

  Specific absorbance rate

  SIS

  Superconductor–insulator–superconductor

  SNS

  Superconductor–normal–superconductor

  SQUID

  Superconducting quantum interference device

  SSM

  Scanning SQUID microscope

  TEM

  Transient electromagnetics

  3.1 Introduction

  The field of electromagnetism is an ever growing one. It has found numerous applications in a wide variety of research and industries. Increased use of electromagnetic field s (EMF s) has led to an increased need to develop improved EMF testing facilities, techniques, and equipment. In the past decade there seems to be an increased interest in assessing the potential hazard caused by the nonionizing electromagnetic emissions on the living matter [1] . The health outcomes of cellular phones has become a public issue due to the steadfast growth of this segment throughout the world since the opening of commercial service in 1983 [2] . There was a drastic increase in the number of users to 10 000 by 1991, in the United States of America alone. This is expected to go up to 6.1 billion worldwide by 2020 [3] . Even though cellular phones transmit very low power, which is 0.6 W with 850 MHz, they are placed very close to the user’s head. These facts increased the need to measure the EMFs in free space as well as material media. All the EMF sensing devices have the common requirements of operating with high frequency and at broader bandwidth. The device should be preferentially be small but nevertheless highly accurate. Two important aspects that should be kept in mind while establishing standards for EMF measurements are: (i) generation of standard or reference EMFs (EMFs complying with some regulations) and (ii) using transfer probes to perform rigorous EM measurements [4]

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  Measurements using Optic and RF Waves

  • Frédérique de Fornel, Pierre-Noël Favennec, Frédérique de Fornel, Pierre-Noël Favennec(Authors)
  • 2013(Publication Date)
  • Wiley-ISTE

    (Publisher)

  Chapter 6Exposimetry – Measurements of theAmbient RF Electromagnetic Fields 1      

  6.1. Introduction

  Any moving electric charge produces an electromagnetic radiation which is propagated in space. This property is at the base of the production of electromagnetic radiations used in the devices of radio, television, telecommunication, heating by microwaves, emission radar. Consequently, any system fed in electricity or with stronger reason containing an aerial element emits an electromagnetic radiation or generates an electric and/or magnetic field in its close or even distant vicinity, that we will characterize in this article using the generic term of RF electromagnetic field. Two concerns emerge from this electromagnetic presence:

  – one relates to the electronic systems and thus electromagnetic compatibility (CEM); – the other is man, as a user, patient and human exposure to the electromagnetic fields induced by non-ionizing radiations (NIR). This last concern comes under the field of hygiene and safety.

  This chapter dedicated to the measurement of the RF electromagnetic fields, in the frequency band concerned with non-ionizing radiations, relates to this last aspect exclusively. Even if it is a question of quantifying the same physical sizes, the differences of objectives, protocols, standardization and regulation and reference frame, measuring apparatus ensure that each concern preserves its own constraints and its characteristics and must be treated separately.

  In order to bring reliable elements of appreciation to the medical persons in charge, the first element consists of quantifying, by measurement, the relevant sizes characterizing the exposure of the man. The object of this article is to describe “the good” practices of laboratories.

  6.2. Definitions

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