Electromagnetic fields in the workplace
I think there will be units of users of different household appliances who do not know that any equipment connected to the ordinary household electrical network ~ 220V 50Hz is a source of electromagnetic field (EMF). Yes, there is an EMF, but few know if it exceeds the maximum permissible norms (PDN) or not. I am an employee of a laboratory in an organization that certifies working places according to working conditions, perhaps many have heard that it was carried out by someone. In the last couple of years, when I was allowed to take measurements, I saw many jobs. Somewhere great, somewhere horrible. At the request of workers, I will tell about some results of measurement of EMF. I’ll just make a reservation that I am not a physicist by education and I don’t know the details of the EMF, but I still have a technical education.
So, the measuring instrument: The meter of parameters of electric and magnetic fields "BE-meter-AT-002" is not a super accurate device. The device allows simultaneous measurements of the electrical and magnetic components of the electromagnetic field in two frequency bands: from 5 Hz to 2 kHz and from 2 kHz to 400 kHz. The document, which shows the PDN when working on the computer SanPiN 2.2.2 / 2.4.1340-03 .
Maximum permissible norms of EMF
In theory, if household appliances are grounded, the EMI readings should be in accordance with PD. In practice, it is in most cases the case. But even with grounding, there are exceptions.
We have a ground loop throughout the building. Each office has two or three computers. When we started to measure, we immediately noticed that the readings in general fit the PDN, but are, so to speak, on the verge. In some workplaces, individual indicators exceeded two or even three times. It was not immediately clear what was the matter. Each computer is connected through an uninterruptible power supply, some bespereboyniki were connected to the network through extension cords (Pilots). In some workplaces, the number of extenders reached three pieces))). The bespereboyniki themselves were mainly located under the feet of the workers, and where on the system unit itself. In the beginning, they got rid of the extension cord, the readings did not change. We decided to try to connect a computer to bypass the bespereboynika and Oh miracle, the readings are normal. Recently, this organization purchased a large batch of APC bespereboynik , in appearance they look like this. Im2-tub-ru.yandex.net/i?id=81960965-39-72
It was unclear why from bespereboynika such a level of EMF. It seems he has a ground wire, all sockets are also grounded. Nevertheless, the result is as follows.
')
The same organization is also a building. In many cabinets, in order to brighten up the everyday life of the workers, there were unpretentious FM radio receivers with power supply, a power cord without grounding. Some stood at a distance from computers, some stood on the desktop, next to the monitor. Having worked for some time on measurements, you are already gaining experience and, with any deviations, you begin to check the connection, look for current consumers without grounding. So turning off the receiver, the readings returned to normal. Another interesting case with the receiver in the same place. The radio itself was about two meters away from the computer. It is not clear to me how the electromagnetic fields were distributed, but at a distance of two meters the readings were twice as large. Repeated measurements three times and without changes. Turning off the radio, the readings returned to normal.
Other organization. The situation is similar to Example 2. The usual situation at each workplace is a desk lamp. In the case of even when the lamp is turned off, there are exceeding PDN. Turn off the lamp from the outlet, everything comes back to normal.
We have two types of lamps in our office, some give 2 times the excess, others 1.5. This is provided that they are connected to the electrical network, but are turned off.
Especially for you I will show results with and without a lamp in the workplace. The energy saving lamp is used. Incandescent bulbs out of stock.
There are such wireless mice, moreover, without power. The so-called induction mouse. It works with a special induction mat, and is fed in an induction manner. When measuring, I can say ofigel, because I have never seen such indications on the magnetic component. Excess 15 times. Disable the mouse, i.e. pad and readings are normal. If I'm not mistaken, many graphics tablets work on the same principle.
A few words about it. Device: Electromagnetic Radiation Level Meter -31.
They made measurements purely for themselves. When the base station is connected to the phone, the phone at this moment does not show signs of a call, there is a strong excess, then after a few seconds the radiation returns to normal. One conclusion, when dialing a number, in the first seconds you should not keep the phone at your head. Yes, the exposure time is quite small, but personally now it’s scary for me immediately after dialing to lean the phone against my ear.
I gave the most frequent and interesting examples. Often there is such an option, there is a ground loop, but the computers are connected through a conventional extension cord without earth, respectively, there are elevations. We change the extension cord with the ground and everything comes back to normal. I can not express any preference about high-quality extension cords with the ground, they all more or less cope with their tasks. As you can see, there are problems with uninterruptible power supplies and table lamps. Even the speakers do not make such noise as table lamps. Here, too, I will not make any recommendations, since each sample must be investigated separately.
About LCD monitors and CRT. If there is grounding, then no matter what type of monitor, the indicators should be normal. Without grounding, CRT monitors have slightly higher LCD monitors.
Especially for the workers of the post , who planted the idea to write this article, measured the outlet where the switch and the router are connected. Of course, the use of PDN for monitors is purely conditional. I made only one measurement to at least estimate the value.
As we see, it exceeds the magnetic component due to the presence of transformers in the power supply units. What to do? Besides the fact that I am not a physicist, I am also not a radio technician)). Apparently somehow you need to shield the transformers.
PS In view of the fact that the doctors themselves cannot decide what harm the EMF causes. Therefore, in the same SanPiNe, it is recommended that during active work at a computer after every hour, a 5-15 minute break should be taken.
About the myth that cactus reduces radiation. I want to upset you, but it is not.
UPD: corrected to electromagnetic fields, so it will be correct.
So, the measuring instrument: The meter of parameters of electric and magnetic fields "BE-meter-AT-002" is not a super accurate device. The device allows simultaneous measurements of the electrical and magnetic components of the electromagnetic field in two frequency bands: from 5 Hz to 2 kHz and from 2 kHz to 400 kHz. The document, which shows the PDN when working on the computer SanPiN 2.2.2 / 2.4.1340-03 .
Maximum permissible norms of EMF
| Electric field strength | |
| in the frequency range 5 Hz - 2 kHz, E1 | 25 V / m |
| in the frequency range 2 kHz - 400 kHz, E2 | 2.5 V / m |
| Magnetic flux density | |
| in the frequency range 5 Hz - 2 kHz, B1 | 250 ntl |
| in the frequency range 2 kHz - 400 kHz, B2 | 25 ntl |
In theory, if household appliances are grounded, the EMI readings should be in accordance with PD. In practice, it is in most cases the case. But even with grounding, there are exceptions.
Example 1
We have a ground loop throughout the building. Each office has two or three computers. When we started to measure, we immediately noticed that the readings in general fit the PDN, but are, so to speak, on the verge. In some workplaces, individual indicators exceeded two or even three times. It was not immediately clear what was the matter. Each computer is connected through an uninterruptible power supply, some bespereboyniki were connected to the network through extension cords (Pilots). In some workplaces, the number of extenders reached three pieces))). The bespereboyniki themselves were mainly located under the feet of the workers, and where on the system unit itself. In the beginning, they got rid of the extension cord, the readings did not change. We decided to try to connect a computer to bypass the bespereboynika and Oh miracle, the readings are normal. Recently, this organization purchased a large batch of APC bespereboynik , in appearance they look like this. Im2-tub-ru.yandex.net/i?id=81960965-39-72
It was unclear why from bespereboynika such a level of EMF. It seems he has a ground wire, all sockets are also grounded. Nevertheless, the result is as follows.
')
Example 2
The same organization is also a building. In many cabinets, in order to brighten up the everyday life of the workers, there were unpretentious FM radio receivers with power supply, a power cord without grounding. Some stood at a distance from computers, some stood on the desktop, next to the monitor. Having worked for some time on measurements, you are already gaining experience and, with any deviations, you begin to check the connection, look for current consumers without grounding. So turning off the receiver, the readings returned to normal. Another interesting case with the receiver in the same place. The radio itself was about two meters away from the computer. It is not clear to me how the electromagnetic fields were distributed, but at a distance of two meters the readings were twice as large. Repeated measurements three times and without changes. Turning off the radio, the readings returned to normal.
Example 3
Other organization. The situation is similar to Example 2. The usual situation at each workplace is a desk lamp. In the case of even when the lamp is turned off, there are exceeding PDN. Turn off the lamp from the outlet, everything comes back to normal.
We have two types of lamps in our office, some give 2 times the excess, others 1.5. This is provided that they are connected to the electrical network, but are turned off.
Especially for you I will show results with and without a lamp in the workplace. The energy saving lamp is used. Incandescent bulbs out of stock.
| E1, V / m | E2, V / m | B1, ntl | B2, nTl |
| The desk lamp does not work, but is included in the electrical network. | |||
| 139 | 0.39 | ten | one |
| 122 | 0.4 | ten | 3 |
| 133 | 0.38 | ten | 3 |
| The table lamp is working (the increase in readings is connected with the “warming up” of the fluorescent lamp after switching on) | |||
| 66 | 8.9 | ten | 3 |
| 79 | 11.4 | ten | four |
| 86 | 12.9 | ten | four |
| The lamp is disconnected from the network. Indications running monitor | |||
| four | 0.02 | ten | one |
Example 4
There are such wireless mice, moreover, without power. The so-called induction mouse. It works with a special induction mat, and is fed in an induction manner. When measuring, I can say ofigel, because I have never seen such indications on the magnetic component. Excess 15 times. Disable the mouse, i.e. pad and readings are normal. If I'm not mistaken, many graphics tablets work on the same principle.
Phone radiation
A few words about it. Device: Electromagnetic Radiation Level Meter -31.
They made measurements purely for themselves. When the base station is connected to the phone, the phone at this moment does not show signs of a call, there is a strong excess, then after a few seconds the radiation returns to normal. One conclusion, when dialing a number, in the first seconds you should not keep the phone at your head. Yes, the exposure time is quite small, but personally now it’s scary for me immediately after dialing to lean the phone against my ear.
Total
I gave the most frequent and interesting examples. Often there is such an option, there is a ground loop, but the computers are connected through a conventional extension cord without earth, respectively, there are elevations. We change the extension cord with the ground and everything comes back to normal. I can not express any preference about high-quality extension cords with the ground, they all more or less cope with their tasks. As you can see, there are problems with uninterruptible power supplies and table lamps. Even the speakers do not make such noise as table lamps. Here, too, I will not make any recommendations, since each sample must be investigated separately.
About LCD monitors and CRT. If there is grounding, then no matter what type of monitor, the indicators should be normal. Without grounding, CRT monitors have slightly higher LCD monitors.
Especially for the workers of the post , who planted the idea to write this article, measured the outlet where the switch and the router are connected. Of course, the use of PDN for monitors is purely conditional. I made only one measurement to at least estimate the value.
| E1, V / m | E2, V / m | B1, ntl | B2, nTl |
| Enabled router and switch | |||
| 36 | 0.15 | 1330 | eight |
| Only router is enabled | |||
| 23 | 0.01 | 520 | 2 |
| Both are disabled | |||
| one | 0.01 | ten | one |
As we see, it exceeds the magnetic component due to the presence of transformers in the power supply units. What to do? Besides the fact that I am not a physicist, I am also not a radio technician)). Apparently somehow you need to shield the transformers.
PS In view of the fact that the doctors themselves cannot decide what harm the EMF causes. Therefore, in the same SanPiNe, it is recommended that during active work at a computer after every hour, a 5-15 minute break should be taken.
About the myth that cactus reduces radiation. I want to upset you, but it is not.
UPD: corrected to electromagnetic fields, so it will be correct.
Source: https://habr.com/ru/post/140431/
All Articles