Microwaves have long been settled in our kitchens, but no one thought about the principle of their work. But there is still debate about whether this device is safe for humans or not. We decided to debunk all the myths and prove that there are microwave ovens in the kitchen!

So that you understand microwave ovens operate at a frequency commensurate with the frequency of a smartphone... Such waves are used in radar, in satellite navigation, even the Sun emits a certain fraction of microwaves.

Microwave radiation itself is hazardous to health.... Imagine if you were influenced by several thousand mobile phones, Wi-Fi routers, or more than a dozen cell towers. I'm talking about the waves with which there is contact. In fact, one powerful magnetron can weld a person's insides and detonate any product in the event of prolonged exposure.

The good news is that manufacturers are tackling this issue with technical and design engineering. Today even inexpensive stoves do no harm and you can vote for them with a ruble. That is why the harm of a modern microwave oven is a myth.

How it works

All appliances - cheap and expensive - work the same way. In fact, this is a metal box, inside which a magnetron, which emits short waves, works. Without getting into the details, kinetic energy is converted into heat energy, which heats up the food.

Microwaves are able to penetrate food to a depth of 1.5 cm, no more... The rest of the layer heats up due to natural thermal conductivity. This principle works in absolutely all models, so one cannot say that some of them are safer than others.

Build quality is another matter. It is the insulation of the chamber that prevents microwaves from escaping outside. Today, all manufacturers are required to equip ovens with protective mechanisms and certify machines for safety.

There are two standards for household appliances that regulate safe radiation:

• our, Russian- according to it, the level of density of microwaves should not exceed 5.0 mW * cm2 at a distance of half a meter from the oven;
• foreign, American (ANSI) considers a density of 10 mW * cm2 to be the norm.

Such a significant difference is due to the fact that our standard was developed by physicians based on the main thing - human health. ANSI is the labor of manufacturers who seek to reduce the cost of products. Irreparable harm is caused by radiation from 60 mW / m2 and that is why every microwave has multi-layered protection.

Build quality and design

This is, so to speak, the basic step of protection. If the technique is not worked out constructively, it can pass the wave. The fact is that you will find ventilation holes in any model. All of them can be considered a source of leakage if their geometric dimensions are greater than the wavelength.

Based on this, the holes should be made in the form of small slots located along the line of current flow in the chamber. For the sake of fairness, I will say that all manufacturers comply with this point, therefore, in the ovens, even near ventilation, a screening effect occurs, - no wave has a chance to penetrate outside.

Door

Microwave doors are considered a potential source of leakage, exacerbated by close proximity of the user.

That is why increased requirements are imposed on their design:

• convenience of observing preparation, easy access to the dish and protection when the door is open;
• strong shielding and no leakage.

Damage can be obtained by opening the device during operation, therefore the first issue is solved by a special design of the locking system. Manufacturers use three or even four protective and interlocking switches. With their help, the magnetron starts only when the contacts are closed (after closing the door). Switch types can be different, for example, Safety Monitor Switch, Door Switch - door switch, Primary / Secondary Switch - primary / secondary.

In terms of choice, the Koreans went farthest. In microwave ovens Samsung many technologies have been implemented, but the MC32F604TCT model turned out to be especially successful. This beast is equipped with a hinged door, like a traditional oven, there are 4 safety switches, a bioceramic coating, and a number of amenities for preparing a variety of dishes.

If you follow the main trend of 2017 - healthy lifestyle, Koreans will help out here too. Model MW3500K absolutely safe and allows you to cook on the airfryer, which makes oil-free meals very healthy. Moreover, many autorecipes are poured in to help you, and this removes an extra headache in everyday time trouble.

Shielding

A clever multi-frame door design is used to provide shielding. The viewing window is always covered with a perforated metal sheet. Each hole in the sheet acts as a diaphragm and prevents leakage. The waves are reflected, return to the camera and simply physically cannot go outside. When choosing, make sure that the hole diameter does not exceed 2.3 mm.

Circuit protection must also be provided as there are gaps between the instrument chassis and the door. The problem is that they can grow during operation. Here the gap between the seal and the chamber is important - the fit must be tight.

Any microwave oven has good shielding, otherwise it would not go on sale... If you are looking for a solo, planning to use it for warming up and defrosting, take a look at the model LgMS-2042DB... For little money, you will get a good usable volume of 20 liters, optimal power, electronic control. Of course, there are no frills and additional options.

Great opportunities can be found among the Germans. For example, a car BoschBFL634GS1 can be built into the furniture profile, there are 7 automatic programs. An inverter motor is working inside. Rounding out this boom of technology is smart touch controls and a bright display.

In addition, I would like to note the line, which is especially loved by professionals. This Rococo-style Electrolux microwave ovens... As the Swedes say, cooking is an art and you are an artist. But, if we leave the lyrics, the series turned out to be really successful: it has a successful appearance and advanced technologies. For example, in the model Electrolux EMM20000OC you can cook even a roast, even a chocolate fondant.

conclusions

A microwave oven is an absolutely harmless device, no worse than a simple smartphone. Even food, despite the intrigues of competitors, does not lose its nutritional value when it comes under the oppression of microwaves. Today you can safely choose budget and expensive models, the main thing is that there is a protective locking system, a screen and a good assembly inside.

Many people have microwaves at home, many have a thought - what is the radiation from a microwave and where is it most intense? I managed to get the answer to this question in the course of the last laboratory work on the subject of Life Safety. In addition, I will tell you about the most effective ways to protect against microwave radiation from a microwave.

Experiment

We carried out the research in the following way. Having installed the antenna at a distance of five centimeters from the oven door, we began to look for the place with the highest radiation intensity, moving the antenna up and down and left and right relative to the door. After a while, we found such a place - a gap between the door and the oven control panel, at the top of the door.

Then, the antenna was gradually removed from the oven with a step of 5 cm, measuring the radiation up to a mark of 50 cm. What did we get. At a distance of 5 cm, the radiation was 466 W / m ^ 2, and at a distance of 40 cm - 22 W / m ^ 2.

And the last part of the experience - we checked the effectiveness of protection with various screens. The most effective screen turned out to be a 2 mm thick sheet of aluminum, installed approximately 2-3 cm from the furnace and fixed for immobility. The measurement results showed the following - at a distance of 40 cm from the furnace, the radiation power was 0.63 W / m ^ 2. It is easy to calculate that the screen reduced radiation by 97.13%.

In addition to the aluminum screen, we tested the following screens: rubber (zero efficiency), metal mesh with a period of 10 mm (low efficiency), metal mesh with a period of 50 mm (average efficiency - the second most efficient) and plywood sheet (zero efficiency).

conclusions

So, there are 3 ways to protect yourself from radiation.

1. Distance protection
2. Time protection
3. Shielding protection

On the first point, we can protect ourselves from microwave radiation simply by not approaching it at a distance of less than 70 cm. Of course, this is not always possible, but just do not stand in front of the microwave and do not look at how the food is heated.

With the second point, I think, everything is also clear. If you are standing close to the stove, try to keep this time to a minimum.

Well, on the third point - protect yourself with an aluminum sheet. =))

Summarizing the results

Now you know where the microwave radiation is most intense and how to protect yourself from it. However, do not wrap yourself in foil and walk in such a suit (if you decide to turn around, do not forget to attach the wires to your leg and to the battery 😆), but just do not stand too close to the microwave looking at how the food is heated and do not look at this process every time you warming something. Just being in the kitchen, you do not risk anything!

Successful holidays and congratulations to all on the sacred holiday - Victory Day !! HOORAY!

All inhabitants of the earth are in the zone of action of various radiation. The human body is adapted to natural sources (solar radiation, radiation background of the earth, electromagnetic waves of atmospheric phenomena), this is a normal living environment. But artificial generators of radiation are a problem for the body.

What are the sources of the electromagnetic field (EMF) around

• Wiring: creates an electromagnetic field around itself, the magnitude of which is directly proportional to the load on the line. That is, when the boiler or electric oven is turned on, the radiation intensity increases many times over.
• Any electrical appliance that contains conductors (windings of transformers, filaments of a hair dryer or a heating coil are a source of radiation). Even if there are no obvious nodes generating radiation.
• Information display devices: screens of TVs, monitors, tablets, laptops, game consoles.
• Acustic systems.
• Electric motors (washing machine, refrigerator, vacuum cleaner, fan, the same hair dryer).
• Electronic measuring devices: electricity meters.
• Places of concentration of electrical wiring: electrical panels, switching nodes for television or Internet cables.
• Electrical appliances that include switching power supplies (from a smartphone charger to a computer and a music center).
• Electric floor heating system.
• Central heating electrical systems.
• Modern economical lighting devices (include power supplies operating at high frequency).
• Microwave (microwave) ovens, or electric ovens with a high-frequency heating unit. This is the scourge of modern civilization: there is such a device in almost every home.

We will separately list the sources of direct radiation for transmitting information.

• Mobile phones, smartphones, tablets with wireless network connection.
• Radiotelephones of the city communication network.
• Portable radios.
• All kinds of wireless devices: headphones, computer mice, keyboards.
• Radio-controlled toys.
• Wi-Fi routers.

And these are just the devices that surround us in the room. That is, located in the immediate vicinity. We can somehow influence this danger by optimizing the modes of use. In this case, the protection against electromagnetic waves is within the responsibility of the owner of the building.

Outdoor radiation sources

We will not talk about radiation: (nuclear power plants, ships, submarines with a nuclear reactor). And also places of extraction, processing and disposal of nuclear fuel and weapons. In these regions, the level of radiation exposure is controlled by special services. Only the choice depends on us: to be in this place or not (accommodation, service, work).

Such zones have the character of a point placement, in contrast to the sources of electromagnetic waves.

• Transformer substations.
• Power lines (overhead and underground). Just like in room wiring - the level of the electric field depends on the load on the line.
• Transmitting antennas: TV towers, radio transmitters, departmental transmitting centers (military, ports, air traffic control rooms).
• Large enterprises that use large-scale electrical equipment.
• Trolleybus lines (unlike power lines, they are located close to places of residence).
• Actually, city transport is powered by electric traction (at the moment when we directly use it).
• Street lighting, advertising LED screens.

All of the above does not mean that each of us is in mortal danger every second. However, we need to know how to protect ourselves from EMF. Or at least minimize its effect on the body. For this, it is not at all necessary to use special means of protection against electromagnetic radiation.

How to protect yourself from the electromagnetic field at home

Why in everyday life? In enterprises where personnel are exposed to an electromagnetic field, special services work. Their area of ​​responsibility includes:

• Making measurements of the EMF level in places where people are present.
• Ensuring a safe level of radiation from sources that cannot be turned off while personnel are in the immediate vicinity.
• Monitoring the time spent by workers in areas with hazardous radiation levels.
• Development of guidelines and requirements for work in the area of ​​exposure to EMF.

The activities of such services are monitored by supervisory authorities. And for us, you only have SES standards, and common sense when using household electrical appliances.

What methods of protection against electromagnetic radiation can be applied at home? There are three main areas of protection:

Time protection

Many people remember how the consequences of the accident at the Chernobyl nuclear power plant were eliminated. The rescuers worked on a strictly controlled schedule: the body can tolerate a certain dose of radiation relatively safely. It's like sunbathing on the beach: sunbathing times are regulated by doctors. Otherwise, the consequences can be sad.

The same goes for radiation from electrical appliances. The general principle is this:

• If the appliance is not in use, it should be turned off.
• If the device cannot be turned off, reduce the time spent in the radiation zone.

In practice, it looks like this:

Distance and direction protection

This method is both simple and difficult to follow. If you know exactly where the active radiation source is, stay as far away from it as possible. In the global understanding of the problem, you should not buy housing in the area of ​​operation of power lines, on the first line from city streets (with trolleybus wires), in the immediate vicinity of industrial facilities or transformer substations.

Additional means of protection against electromagnetic radiation

Of course, we will not discuss metallized nets for carrying a mobile phone in a pocket, or mythical neutralizers of radiation in the form of jade pyramids. These “remedies” were popular during the wild market era of the 90s. Various active "jammers" are also nothing more than an effective means of extracting money from the client. In addition, any electrical device, and even more so with a radiator, is another source of electromagnetic waves.

Important!
From the point of view of the theory and practice of the propagation of radio waves (as well as any other electromagnetic radiation), the only method of protection is a conductive screen, grounded in accordance with the Electrical Installation Code.

How to apply the method in practice

True, these means of protection have a side effect: a cellular signal does not penetrate through such walls and windows. Radio and TV broadcasts will also be received only on an external antenna. Considering the health benefits, this is not a problem.

• And household appliances located inside must be connected to the ground bus. Most electrical equipment has a metal case (even plastic TVs and stereos at first glance have a conductive frame inside). The level of radiation from grounded equipment approaches zero.

How to know if you are at risk of EMF radiation

Forewarned is forearmed. Try to find out as accurately as possible everything about your electrical appliances in terms of exposure to the electromagnetic field. You may need to invite SES specialists. The cost of identifying harmful devices will pay off in maintaining health.

This applies to your home. On the territory of general use, as well as at enterprises (in offices), sanitary standards are in force. If you have a suspicion that these norms are violated (unmotivated deterioration of the condition, interference on the TV, music player) - contact the SES department. Either you will receive a comforting answer that nothing threatens your health, or the responsible authority will take measures to eliminate the danger.

Related Videos

Explanations are given on the harmful effects of microwave radiation, their regulation and methods of determination. LABORATORY WORK PROTECTION AGAINST ULTRA-HIGH FREQUENCY RADIATION The purpose of the work is to get acquainted with the characteristics of electromagnetic radiation with the principle of establishing regulatory requirements for electromagnetic radiation, to measure electromagnetic radiation in the microwave range depending on the distance to the source and to evaluate the effectiveness of screens made of various materials. The spectrum of electromagnetic EM oscillations is within wide limits along the length ...

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MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION

KAMSK STATE ENGINEERING AND ECONOMIC ACADEMY

INSTRUCTIONS

for laboratory work

on the course "Life Safety"

Naberezhnye Chelny

2006

UDC

Protection against microwave radiation: Methodological instructions for laboratory work on the Belarusian railways / Compiled by I.M. Nuriev, G.F. Yusupova. - Naberezhnye Chelny: Kampi. 2004 .-- 15s.

Methodical instructions are intended for students of all specialties of full-time and part-time education. Explanations are given on the harmful effects of microwave radiation, their regulation and methods of determination. The procedure for the experiment and the presentation of the results obtained are proposed.

Reviewer: Doctor of Technical Sciences, Professor of the Department of MITLP N.N.Safronov.

Published by the decision of the Scientific and Methodological Council of the Kama State Polytechnic Institute.

LABORATORY WORK

PROTECTION AGAINST ULTRA HIGH FREQUENCY RADIATION

Objective - familiarize yourself with the characteristics of electromagnetic radiation, with the principle of establishing regulatory requirements for electromagnetic radiation, measure electromagnetic radiation in the microwave range depending on the distance to the source and evaluate the effectiveness of screens made of various materials.

1. GENERAL INFORMATION

Electromagnetic fields (EMF) are generated by currents that change over time. The spectrum of electromagnetic (EM) oscillations is within wide limits along the wavelengthλ: from 1000 km to 0.001 μm or less, and in frequency: from 3 * 10 2 to 3 * 10 20 Hz, including radio waves, optical and ionizing radiation. At present, EM energy of the non-ionizing part of the spectrum is most widely used in various industries. This applies, first of all, to EM fields of radio frequencies. They are subdivided by wavelength into a number of ranges (Table 1).

The EM field consists of an electric field due to the voltage on live parts of electrical installations, and a magnetic field that occurs when current passes through these parts. EMF waves travel long distances.

Table 1

Range name	Wavelength	Frequency range	Frequency	According to international regulations
								Frequency band name	Number
Long waves (LW)	10 - 1 km	Treble (HF)	3 - 300 kHz	Low (bass)
Medium waves (CB)	1 - 0.1 km	Also	0.3 - 3 MHz	Average (midrange)
Short wave (HF)	100 - 10 m	Also	3 - 30 MHz	High (HF)
Ultrashort waves (VHF)	10 - 1 m	Treble (UHF)	30 - 300 MHz	Very high (VHF)
Microwave: decimeter (dm); centimeter (cm); millimeter (mm);	100 - 10 cm 10 - 1 mm 1 cm - 1 mm	Ultrahigh frequencies (microwave)	0.3 - 3 GHz 3 - 30 GHz 30 - 300 GHz	Ultrahigh (UHF) Ultrahigh (UHF) Extreme (EHF))

table 2

The EMF component, by which its impact is assessed, and the frequency range, MHz	Maximum permissible EMF intensity during the working day
Electrical component: 0.06 - 3 3 - 30 30 - 50 50 - 300	50 V / m 20 V / m 10 V / m 0.5 V / m
Magnetic component: 0.06 - 1.5 30 - 50	5.0 A / m 0.3 A / m

In industry, sources of EMF are electrical installations operating on alternating current with a frequency of 10 to 10 6 Hz, automation devices, electrical installations with an industrial frequency of 50 - 60 Hz, high-frequency heating installations (drying wood, gluing and heating plastics, etc.). In accordance with GOST 12.1.006-84, the values ​​of the maximum permissible intensity of EMF of radio frequencies in the range of 0.06 - 300 MHz at workplaces are given in Table 2.

The maximum permissible levels (MPL) for the electrical component, according to, should not exceed 20V / m, and for the magnetic component - 5A / m. EMF is characterized by a combination of alternating electrical and magnetic components. Different ranges of radio waves are united by a common physical nature, but they differ significantly in the energy contained in them, the nature of propagation, absorption, reflection, and, as a result, in the effect on the medium, incl. and per person. The shorter the wavelength and the higher the vibration frequency, the more energy the quantum of EM radiation carries. The relationship between energy E and frequency fluctuation is defined as:

E = h  or, since the wavelength λ and frequency are related by the relation = c / λ,

E = h c / λ,

where: c is the speed of propagation of electromagnetic waves in the air (c = 3 * 10 8 m / s), h is Planck's constant equal to 6.62* 10 -34 W / cm 2.

The EMF around any radiation source is divided into 3 zones: the near zone is the induction zone, the intermediate zone is the interference zone, and the far zone is the wave zone. If the geometric dimensions of the radiation source are less than the radiation wavelength λ (i.e., the source can be considered as a point source), the boundaries of the zones are determined by the following distances R:

• the near zone (induction) of the wave formation is at a distance R< λ/2π;
• intermediate zone (interference) - the presence of maxima and minima is located at a distance of λ / 2π < R < 2πλ;
• far zone (wave) - the radiation zone is at a distance R> 2πλ.

Those working with sources of Radiation LF, MF and, to a certain extent, HF and VHF ranges are in the induction zone. When operating generators of the microwave and EHF ranges, those working are often in the wave zone.

In the wave zone, the field intensity is estimated by the energy flux density (PES), i.e. the amount of energy falling per unit surface area. In this case, the PES is expressed in W / m 2 or derived units: mW / cm μW / cm 2. The EMF rapidly decays with distance from the radiation source. EM waves of the UHF, UHF and EHF range (microwaves) are used in radar, radio astronomy, radio spectroscopy, geodesy, defectoscopy, physiotherapy. Sometimes UHF EMFs are used for rubber vulcanization, heat treatment, food products, sterilization, pasteurization, and reheating of food products. Microwave devices are used for microwave therapy.

The most dangerous for humans are EMFs of high and ultrahigh frequencies. The criterion for assessing the degree of exposure to EMF on a person can serve as the amount of electromagnetic energy absorbed by him when he is in an electric field. The amount absorbed by a person: the energy depends on the square of the strength of the current flowing through his body, the time spent in the electric field and the conductivity of the tissues of the person.

According to the laws of physics, changes in a substance can only be caused by that part of the radiation energy that is absorbed by this substance, and the energy reflected or passing through it has no effect. Electromagnetic waves are only partially absorbed by the tissues of a biological object. Therefore, the biological effect depends on the physical parameters of the RF EMF: the wavelength (vibration frequency), the intensity and mode of radiation (continuous, intermittent, pulse-modulated), the duration and nature of the body's irradiation, as well as the area of ​​the irradiated surface, and the anatomical structure of the organ. or fabric.

The degree of energy absorption by tissues depends on their ability to reflect it at the interface, which is determined by the water content in the tissues and their other features. Oscillations of dipole water molecules and ions contained in tissues lead to the transformation of the electromagnetic energy of the external field into thermal energy, which is accompanied by an increase in body temperature or local selective heating of tissues, organs, cells, especially those with poor thermoregulation (eye lens, vitreous humor, testes, etc.) etc.). The thermal effect depends on the intensity of the irradiation. The threshold intensities of the thermal effect of EMF on the animal body are for the range of medium frequencies - 8000 W / cm 2, high - 2250 W / cm 2, very high - 150 W / cm 2, decimeter - 40 mW / cm 2, centimeter - 10 mW / cm 2 , millimeter - 7 mW / cm 2.

EmF with a lower intensity does not have a thermal effect on the body, but it causes weakly pronounced effects of a similar orientation, which, according to a number of theories, is considered a specific non-thermal effect, i.e. the transition of EM energy in an object into some form of non-thermal energy. Hormonal imbalance in the presence of a microwave background in the workplace should be considered as contraindications for professional activities associated with nervous tension at work and frequent stressful situations.

Permanent changes in the blood are observed with a PES above 1 mW / cm 2. These are phase changes in leukocytes, erythrocytes and hemoglobin. Damage to the eyes in the form of clouding of the lens (cataracts) - the consequences of exposure to EMF in industrial conditions. When exposed to millimeter waves, changes occur immediately, but quickly pass. At the same time, at frequencies of about 35 GHz persistent changes occur as a result of damage to the corneal epithelium.

Clinical studies of people exposed to industrial exposure to microwave radiation at its intensity below 10 mW / cm 2, showed the absence of any manifestations of cataract.

Exposure to EMF with levels exceeding the permissible levels leads to changes in the functional state of the cardiovascular and central nervous systems, disruption of metabolic processes. When exposed to significant intensities of the microwave field, a more or less pronounced clouding of the lens of the eye (cataracts) may occur. Changes in the composition of the blood are often noted.

In accordance with sanitary norms and rules, when working with sources of EMF of microwave frequencies, the maximum permissible intensity of EMF at workplaces is given in table. 3.

Table 3

In the microwave range (300 MHz - 300 GHz)	Maximum allowable intensity
1. For those working under irradiation and current: 1) whole working day 2) no more than 2 hours per working day 3) no more than 15-20 minutes per working day	10 μW / cm 2 100 μW / cm 2 1000 μW / cm 2
2. For persons not professionally related, and for the population	1 μW / cm 2

Protective measures against the action of EMF are mainly reduced to a decrease in radiation in the source, a change in the direction of radiation, a decrease in exposure time, an increase in the distance to a radiation source, to the use of protective shielding, remote control of devices emitting EM waves; the use of personal protective equipment. Protective screens are divided into:

1) reflective radiation;

2) absorbing radiation.

The first type includes solid metal screens, screens from a metal mesh, from a metallized fabric. The second type includes screens made of radio-absorbing materials. Personal protective equipment (PPE) includes: overalls made of metallized fabric: protective gowns, aprons, capes with a hood, gloves, shields, as well as safety glasses (at an intensity above 1 mW / cm 2), whose glasses are covered with a layer of semiconducting tin oxide, go mesh glasses in the form of half masks made of copper or brass mesh.

2. CONTENT OF WORK

2.1. DESCRIPTION OF THE STAND

The stand is shown in Fig. 1.. The stand is a table made in the form of a welded frame with a table top 1, under which replaceable screens 2 are placed, used to study the shielding properties of various materials. On the countertop 1 there is a microwave oven 3 (a radiation source of EM oscillations with = 2.45 GHz, wavelength = 12.5 cm) and coordinate device 4.

Coordinate device 4 registers the movement of the microwave field sensor 5 along the "X", "Y" axes. Coordinate "Z" is determined by the scale, marked on the measuring stand 6, but which the sensor 5 can move freely. This makes it possible to investigate the distribution of microwave radiation in space from the side of the front panel of the microwave oven (elements of the most intense radiation).

The sensor 5 is made in the form of a half-wave vibrator designed for a frequency of 2.45 GHz and consisting of a dielectric body, vibrators and a microwave diode.

The coordinate device 4 is made in the form of a tablet, on which a coordinate grid is applied. The tablet is glued directly to the tabletop 1. The stand 6 is made of a dielectric material (organic glass) to exclude distortion of the microwave field distribution.

As a load in the microwave oven, a building red brick is used, installed on a fixed stand, which is used as a shallow earthenware plate, which ensures the stability of the measured signal.

The signal from the sensor 5 goes to the multimeter 7, placed on the free part of the tabletop 1 (outside the graticule).

The tabletop 1 has slots for installing replaceable protective screens 2 made of the following materials:

galvanized steel mesh with mesh of 50 mm;

galvanized steel mesh with 10 mm meshes;

aluminum sheet;

polystyrene;

rubber.

Fig. 1

2.2. TECHNICAL CHARACTERISTICS OF THE STAND

2.2.1 Range of flux density of electromagnetic radiation in the studied area of ​​the microwave oven, μW / cm 2 0...120.

2.2.2 Ratio between the readings of the М3900 multimeter and the PZ-19 flux density meter:

1 μA = 0.35 μW / cm 2.

2.2.3 Values ​​of displacement of the sensor relative to the microwave oven, mm, not less:

along the X-axis 500

along the "Y" axis ± 250

along the "Z" axis 300

2.2.4 Microwave oven power, W, no more than 800

2.2.5 Number of replaceable protective screens 5

2.2.6 Screen sizes, mm (330 ± 5) x (500 ± 5)

2.2.7 Power consumption, VA, no more: 1200

2.2.8 Scale division along the X, Y, Z axes, mm 10 ± 1

2.2.9 Overall dimensions of the stand, mm, no more:

length 1200

width 650

height 1200

2.2.10 Stand weight, kg, no more than 40

2.2.11 Power supply of the stand must be carried out from the AC mains

voltage, V 220 ± 22

frequency, Hz 50 ± 0.4

2.2.12 Operating mode of the microwave oven:

Duration of work, min, no more than 5

• the length of the break between

working cycles, s, not less than 30

Power level, 100%

2.3. SAFETY REQUIREMENTS FOR PERFORMANCE OF LABORATORY WORK

2.3.1. Students who are familiar with the structure of the laboratory stand, the principle of operation and safety measures during laboratory work are allowed to work.

2.3.2. Only enable installation with instructor permission.

2.3.4. Do not adjust or repair the door, control panel, interlock switches or any other part of the oven yourself. Repairs should only be carried out by specialists.

2.3.5. The microwave oven must be grounded.

2.3.6. It is not allowed to switch on and operate the oven without load. It is recommended to leave a brick in the oven between working cycles. If the oven is accidentally turned on, the brick will act as a load.

2.3.7. Keep the instruments of the laboratory setup energized only during the experiment.

3. ORDER OF LABORATORY WORK

3.1. Familiarize yourself with the safety measures during laboratory work and strictly follow them.

3.2. Connect the microwave oven to the AC mains.

3.3. Put a brick in the oven on a support (inverted plate).

3.4. Set the oven operating mode in accordance with clause 2.2.12. in accordance with the passport for a specific microwave oven.

For the Pluto microwave oven, it is switched on in the operating mode in the following sequence: open the door by pressing the rectangular button in the lower part of the front panel; set the "power" knob to the extreme right position; set the "time" knob to the 5 min position; close the door tightly.

3.5. Place the sensor at 0 on the X-axis of the coordinate system.

Moving the sensor along the Y-axis of the coordinate system and the Z-axis (on the rack), determine the zones of the most intense radiation and, using a multimeter, fix their numerical values. Moving rack with sensoralong the X coordinate (removing it from the oven to the maximum mark of 50 cm), take the multimeter readings discretely with a step of 20 mm. Enter the measurement data in Table 4. Construct a graph of the distribution of radiation intensity in the space in front of the oven.

3.6. Place the sensor at 0 in the X-axis. Record the multimeter reading.

3.7. Install protective screens one by one and record the readings of the multimeter.

3.8. Determine the shielding efficiency for each screen using the formula:

(1)

where I is the reading of a multimeter without a screen;

I e - reading of a multimeter with a screen.

3.9. Build a diagram of the effectiveness of shielding from the type of material of protective shields.

3.10. Draw up a report on the work.

4. REPORT ON LABORATORY WORK

4.1. General information

4.2. Stand layout

4.3. Measurement data (tables 4 and 5)

Table 4

Measurement number	X value, cm	Y value, cm	Z value, cm	Radiation intensity (multimeter reading)
. . .

Table 5

Screen numbers	Shielding efficiency, δ

4.4. Graphs of the distribution of radiation intensity in space and a diagram of the effectiveness of shielding from the type of material of protective screens.

Control questions

1. What is the source of EMF in the technosphere?
2. What characteristics are used to assess the magnitude of the electromagnetic field?
3. How does EMF affect the human body?
4. By what principle is the industrial frequency EMF standardized?
5. By what principle is the RF EMF standardized?
6. Are people affected by radar emissions?
7. What are the ways to protect a person from high levels of EMF?
8. What is the physical principle of operation and how is the effectiveness of EMI shielding evaluated?
9. What are the current hygienic limit standards for permissible levels of exposure to EMF on a person during professional and non-professional exposure?

literature

1. Occupational Safety and Health. G.F. Denisenko, - M .: Higher school, 1985. –319p.
2. Labor protection in the chemical industry. G.V. Makarov. - M .: Chemistry, 1989 .-- 496p.
3. Safety manual. P.A. Dolin, - M .: Energoatomizdat, 1984.
4. Safety precautions in electric power installations. Reference book P.A. Valleys. - M .: 1987.
5. Life safety. / Ed. S.V. Belova - M .: Higher school, 2005. –606s.
6. GN 2.1.8./2.2.4.019-94. Temporary permissible levels (TDL) of exposure to EMR generated by a cellular communication system.
7. GOST 12.1.002-84. Occupational safety standards system. Electric fields of industrial frequency. Allowable tension levels and requirements for control at workplaces.
8. GOST 12.1.006-84. Radio frequency electromagnetic fields. General requirements.
9. GOST 12.1.045-84. Occupational safety standards system. Electrostatic fields. Workplace tolerances and inspection requirements.
10. The influence of electromagnetic radiation on human life and methods of protection from it. Tutorial. S.G. Zakharov, T.T. Kaverzneva. - SPGTU; 1992, -74s.
11. Labor protection in the radio and electronic industry. Edited by S.Sh. Pavlov. - M .: Energy; 1986.
12. SanPIN 2.2.4 / 2.1.8.055 - 96;
13. Infrared radiation GOST 12.1.005 98, SanPiN 2.2.4.518 96;
14. Ultraviolet radiation CH 1557 - 88;
15. Laser radiation CH 5801 - 91;
16. SanPiN 2.2.4.1191-03 Electromagnetic fields in industrial conditions.

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Today, everywhere in the world, electromagnetic radiation surrounds us all the time, and no one can completely protect oneself from them, but We All can minimize the harmful effects of the electromagnetic fields that surround us.

Common areas.
In the cities of the Republic of Belarus, the sources of the highest level of radiation are: electric transport (trolleybuses, trams, and especially with a high supply - electric trains and metro) and overhead power lines (PTL), which transmit from 400 volts to 330,000 volts. The hazard level differs many times depending on the value of the transmitted power line voltage. For example, 330 kV (you can see it near the Moscow Ring Road, going from the CHPP), it is outrageous, so they are especially dangerous. Any construction of buildings and houses is prohibited near high-voltage lines, because the most effective method of reducing the harmful effects of radiation on people is distance protection.

It is also worth avoiding places with television and radio broadcasting signals nearby. In the near future, due to the widespread transition to digital broadcasting and the abandonment of traditional analogue TV broadcasting, there will be a significant decrease in the emission of signal transmitters, because digital television at the same broadcasting level requires a much lower level of repeater power.

Mobile connection.
Today, due to the widespread use of mobile communications, it is imperative to take measures to protect yourself from its harmful effects. Recent studies convincingly prove the harm to humans, not only of mobile phones, but also of Wi-Fi hotspots.

Electrical wiring and appliances.

Many people mistakenly believe that if nothing is plugged in, then it is safe. This is a delusion, as long as the machine is turned on and there is voltage on the outlet or switch, they will be sources of radiation, as well as wires or cables in the wall or a TV, a printer in standby mode or a table lamp plugged into an outlet, an electric kettle, etc.

Just protect yourself - place places for a long rest or pastime further away from electrical appliances, sockets, lamps, switches, electrical wiring running in the wall.
Unplug unused TV, printer, computer from the network. And devices with a metal case (microwave oven, refrigerator, washing machine) will emit much less if their cases are grounded by connecting sockets with three-wire electrical wiring to sockets with grounding contacts.

Personal computers and laptops.
Today, everyone in the house, and more than one computer or laptop. You need to remember and observe the following: place the system unit further, preferably under the table, and in no case hold the laptop on your lap. Don't forget to take breaks from work!

General recommendations!
If possible, limit the simultaneous operation of electrical appliances around you! So my acquaintance, who works in an office at a computer, when he comes home, turns on the TV immediately, an electric kettle, a microwave oven, a laptop and still has time to talk on a mobile phone. And no wonder he has a headache when it's time to go to bed!

Take care of your health! I do not recommend getting hung up on protection against electromagnetic radiation. It is better to try to adhere to the above recommendations as much as possible. And at least once a week, do unloading, leaving the city for nature, farther from modern devices and benefits!

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