# Isotropic IoT-Based Magnetic Flux Density Meter Implementation for ELF Field Measurements +
## 1 Introduction  
Multiple studies have demonstrated that long-term exposure to significant extremely low-frequency (ELF) magnetic fields (1 Hz-100 kHz) can result in severe health issues. A considerable rise in blood triglycerides, a putative stress indicator in humans, the disorientation of chicks, and a reduced response time in monkeys are some unsettling effects of exposure to ELF fields [1]. Although some other research shows no link, epidemiological studies show a positive association between residential/domestic and occupational exposure to ELF fields and several forms of cancer, such as childhood leukaemia [2]. Magnetic fields (MFs) depend on the radiation's type, field, frequency, and wavelength. Depending on the current feed, either static magnetic fields (SMF) with direct current (DC) or alternating magnetic fields (AMF) with alternative current (AC) are created. In contrast to SMFs, the polarity of an AMF remains constant despite periodic changes in the direction of the current flow. Several devices create powerful low-frequency magnetic fields such as transformers, electric motors, electric heaters, hair dryers, power supplies, and cathode ray tubes (CRTs), as well as the production, distribution, and consumption of 50 or 60 Hz electric energy. In medicine, magnetic resonance imaging (MRI) uses strong SMF, and the patients are often subjected to between 1.5 and 3 T. The public has occasionally expressed great concern about the use of some of these devices as sources of high magnetic fields. Depending on the exposure source and the distance from that source, magnetic field strengths might vary significantly. Depending on how well the opposing magnetic flux lines cancel each other out or how well the current-carrying lines are balanced, the rate at which the field intensity decreases with distance might differ from one source to another. At an increasing distance, fields from coils, magnets, or transformers degrade quickly by a factor of \(1/\tau^{3}\). In power lines, partial field-cancelling causes the drop-off to be \(1/\tau^{2}\) when currents flow in opposite directions. When there is an imbalanced current, the field intensity decreases more slowly than \(1/\tau\), as shown in Figure 1[3]. The methodology of Extremely Low Frequency (ELF) measurements as defined by the International Telecommunication Union (ITU) is quite complex. Contrary to the measurement of high-frequency fields, extremely low-frequency fields present difficulties in their measurement, since at these frequencies the corresponding wavelengths exceed 100 m, thereby making it difficult to accurately measure in the near field [4]. It should be noted that the quantities of electric field strength, magnetic field strength, and equivalent power density are used to determine public exposure using suitable measuring devices. Regarding exposure to magnetic fields for public safety, the measured values should satisfy the mathematical Equation (1):  
\[\sum_{\rm{IHz}}^{150\rm{KHz}}\frac{H_{i}}{H_{Li}}\leq 1 \tag{1}\]  
where \(H_{i}\) is the measurement of the magnetic field strength and \(H_{Li}\) is the reference level for exposure at frequency \(i\), as reported in Table 1, noting that the electromagnetic radiation limits according to Greek legislation correspond to 70% of the values that are described. The Weighted Peak Method (_WPM_) [5] was established by the ICNIRP 2010 guidelines for non-sinusoidal multiple-frequency fields. This method, incorporated into Directive 2013/35/EU [6], is required for the assessment of electrostimulation effects (non-thermal) at LF/ELF frequencies and is mandatory in all industrial applications for the safety of workers. Figure 1: The magnetic field intensity decreases with the growing distance from the field with fast (\(1/\tau^{3},1/\tau^{2}\)) or slow (\(1/\tau\)) drop-off [1].