Electromagnetic interactions of metal detectors

Electromagnetic interactions of metal detectors

17 Aug2018
Electromagnetic interactions of metal detectors

Abstract
This paper examines the levels and spectra of electrical and electromagnetic fields generated by the metal detector gate. Identification systems around us use deliberate emission of electromagnetic waves as an acting medium that affects humans and their environment. Using the ESM-100 field gauge, it was possible to determine the distribution of the intensity values ​​from several selected gate systems. These values ​​were compared to the current intensity limit.
Introduction
At the present time, interest in anti-theft technologies and systems to identify terrorist threats has increased. Some of these technologies use electromagnetic radiation to find metals. The metal detectors were produced for military purposes - mines with metal construction can be found with detectors. At the moment, industrial metal detectors and entertainment are dominating the market, while gates are used to find metals in courts and airports. Industrial samples are mainly used to find water pipes, gas or underground lines or inside building walls. A large group of detectors are installed devices that are used in public areas, airports, and other enclosed areas for protection purposes.
Several applications and the increasing popularity of these detectors have led to the need for scientific studies on the effects of the radiation emitted by such devices on human organisms, and the results determine the legal level of the permissible intensity of the waves of these devices.
Metal detectors in the gates
Gates related to finding metals in airports and other public places have been expanding. At present, microprocessor-controlled metal detector gates are used with special parameters for tracking and detecting at airports and courts. They have a wide range of tracking that includes a few vertical and horizontal ranges. Special models of this machine can detect metal objects in more than 30 different locations. Increasing tracking limits makes it possible for more people to cross the gate every minute, and with high precision, where more searches are needed. Different prohibited objects are recognizable, and the objects allowed can be omitted depending on the program selected for the device and its sensitivity settings. The tracking range covers a range from floor to top of the detector.
The metal detector gate must meet stringent security standards. On the one hand, there is a group of EMD standards (enhanced metal detectors) in the light of the TSA, NIJ 0601.02 for metallic gates, related to the finding of a gun and a 3-Gun FAA test (Federal Aviation Administration) And, on the other hand, the metal detector before entering the market should meet the requirements of EMC (electromagnetic compatibility) and also CSA, TEC, CB and ICNIRP (International Commission on Non-ionizing Radiation Protection) and international requirements and The environment.
There are two types of tools that are used in public spaces of particular importance. People are inspected through electromagnetic gates and manual metal detectors. In contrast, luggage and objects carried by individuals / travelers are examined by X-ray devices.
At the time of checking the gates, the person stands in an electromagnetic alternating field. Its value can only be in accordance with applicable standards. Therefore, the intensity of both electrical and magnetic components can not exceed the threshold applied to people permanently residing in the field. However, the person who passes through the gate, is subjected to irradiation due to the fact that it is completely in the gate for a few seconds.
Analysis of the distribution of H and E intensity
The analysis done in this article is based on our research, which is done on two types of detectors. Measurements were made in 2016. One of the detectors was placed in the courts of Lublin and the other at the gateway, which was used at the airport. Due to security regulations, little information is available on the performance of this type of equipment. Therefore, the analysis of possible electromagnetic interactions of the above-mentioned systems is presented on human organisms.
The usual principle of tracking performance is based on changes in the amount of magnetic induction. Detecting transmitter and receiver signals in the detector allows the proper operating conditions, including sirens, to be activated. The changes detected in induction values ​​can be due to eddy induced currents in metallic objects that are located on the coil surface of the transmitter. The effect of eddy currents will be the reaction of the magnetic field generated by the magnetic field with the receiver cross section. Adherence to interactions leads to a deviation from the operating mode that triggers the siren's illumination.

The final solutions are completely different, and are often backed up by patents and patches.
The ESM100 sensor, used for research in this paper, has an isotropic magnetic field sensor to measure both the magnetic field and the magnetic component in the frequency range of 5 to 400 kHz. Because of the metal components of the sensor, it was necessary to take a specific measurement procedure that did not require long-term measurements until the siren was sounded.
Measurements were performed in two steps. In the first period, the spatial distribution of the intensity of electrical and magnetic components was determined. By removing the gauge at specified intervals (every 10 centimeters) of the gate walls, the values ​​and trends of the variation of intensity were determined. The test was performed on three axes - the main axis in the center of the gate with two lateral axis at 30 degrees outside the right and left of the gate. The geometry of axis measurement and values ​​are presented in Fig. 3. The apparent observed tendency of reducing the magnetic induction (magnetic field intensity) is significantly reduced by gradually increasing the distance from the active gate segment.
The measurements were carried out at a height of 1 meter from the ground.
The next step in relation to the severity of the senassation was at the closest distance from the gate walls in the height function. Measurements were made every 15 cm once, starting from the bottom of the walls of the gate. The values ​​obtained explicitly showed the presence of two "active" sites that had passive coil sections, as well as "passive" sections that had the recipient level.
In addition to the intensity trajectory during the test, the detection of electromagnetic waves was also carried out. The spectral form obtained through the digital Rigol E102 digital oscilloscope showed that both the frequency and magnitude of the two sensors regulate the metal detector's signal. We found the coordination components in the signal range from 4kHz to 48kHz.
The second tracking system is a common system used in certain areas, such as airports. The system is generally larger, and is designed to scan more people by extending the tracing of personal objects and luggage through the X-ray system.
Like previous gates, testing included several sections. The first step was to determine the parameters of magnetic and electric fields along the transmission axis along with the entire length of the inspection system. Measurement distances were determined every 20 cm once and the measurement height was 1 meter above the ground.
Maximum viewing values ​​from the electric and magnetic field for the first gate were 86.9 μT (70 A / m) and 554 V / m. In the case of the second test, the highest observed values ​​of the field were 41 μT (33.4 A / m) and 254 V / m respectively. Valid values ​​are not higher than the 2016 revised regulations (Table 1). In the case of handheld metal detectors, it should be noted that their emissions are lower. The manually scanned Terascan ESH-10 scanner measures a few hundred times smaller - a magnetic induction of about 100 nT and a magnetic component of 40 V / m.
The state of compatibility of electronic medical devices is completely different. As reported by the industry, abnormalities affecting the heart rate regulator are in fact due to the transition to a "steady state" frequency and is completely safe for the patient. Neurotransmitters and auto electrocutroscopes also do not show an adverse reaction to the field. But the function of the Holter monitor is interrupted.
Observed rates and exposure times for those who are rarely involved with metal detectors, such as airport travelers, are completely safe. But widespread use of tracking systems in many public institutions and anti-theft systems in stores, increases the intensity of the effects of waves.
Conclusion
With regard to most of the equipment used and produced, there is no need for measurement and assessment of exposure to electromagnetic fields. Researches confirm the existence of a safe area. Independent research, however, is a reflection of the concerns of users of metal detectors and those who stand next to them, as well as the statements and conclusions of many research studies that still have the potential for chronic complications, even when exposed to fields. Show a weak ratio.
In the human body exposed to the electromagnetic field, an electrical current is created which affects the frequency of the field. For example, in medium to medium frequencies, nerve and muscle tissue may be stimulated, and in radio frequency and microwave frequencies, tissue temperature increases within the body or the skin surface. Induced currents can disrupt and stimulate electrophysiological processes in the nervous and muscle cells.
The researchers have allowed the relevant institutions to do this research, but there have been some restrictions on the disclosure of sensitive information that has been made in relation to security issues.

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