What are the Problems & limitations in Professional Tests? time of measurements, the equipment used, the way it is operated &more, all affects the outcomes.
Sometimes it is not enough to invite a professional radiation tester. The reason is that there are some differences between the world of professional measurement and the real world.
These differences (caused by problems and limitations in the standards, meters, calibration, and knowledge) usually affect the outcome of the tests (mainly if you order a professional tester that works according to ICNIRP’s standards and guidelines).
In the following paragraphs, I will try to explain the problems and limitations of EMF testing.
The perception and understanding of the risk from EMF
A professional tester that is aware of the risk of exposure to EMF (RF or/and ELF) will more likely perform the test in a better and sticker way. A professional tester that does not acknowledge the risk of exposure to EMF in relatively low levels will most likely will not pay attention to low levels (which can still cause symptoms with EHS people or which can still be considered unhealthy ), will not pay attention to indoor ELF and RF sources (like cordless phones, WIFI routers and other), and is more likely to operate the meter in a way that will show lower levels (for example the average function).
This is why it is extremely important to make sure that the professional tester that you want to hire acknowledge and understands the risk. In some countries, according to the regulations, the tester might not be able to write that relatively low levels pose a risk, but he will still be able to warn you and to give you tips to reduce exposure.
A one time job when the levels change all the time
The levels being measured are relevant only for the time and date that they were measured in. Since the levels of RF and ELF EMF are changing according to the demand, a single time measurement is not very helpful.
When doing the measurement using a home-use EMF meter it is possible and recommended to repeat the measurement several times, in different hours and days, until the radiation pattern and high peak hours are revealed. Since the measurement of a professional tester is a one-time event, it is recommended to ask him to come in peak hours.
Not allowed to measure EMF from in house appliances
In some countries, professional testers are not allowed to measure RF and ELF levels from in-house appliances and devices.
So-called “Safety standards”
In most countries, professional testers have to follow the ICNIRP of FCC/IEEE so-called safety standards. Since these standards are so high, every test outcome would be within standards norms. In some cases, the levels measured will be reported as a percentage of these none protective standards, which will create the impression that these levels are very low. Please press here to read more about ICNIRP’s, WHO’s, other countries and our recommendations for reasonable RF and ELF exposure levels..
Averaged measured levels
In most countries, the “Safety Servery” protocol directs the professional testers to measure only the averaged level over a number of seconds or minutes. Professional safety meters can be set up to show the average level. The outcome of such measurement will usually be very low because modern digital RF signals are usually changing all the time, with many short transmissions (uSec, nSec, and mSec). This way of testing was OK in the analog world because In the old analog RF world the signals were slowly changing and pretty much constant (for example AM).
For example, the WIFI signal is very fast-changing, frequency hopping, and spectrum spread. The signal from a WIFI router that is not sending data to any PC or tablet is transmitting a Bicon signal in MAX output level possible, for 10 short bursts every second. The average of this signal is very low since most of the time it is OFF. But there is 10 max power burst every second (that are missed or are being averaged with 0 by the meter).
In most professional testing equipment there is a possibility to set up the meter to measure peak or average levels. Most professional testers uses the average mode and report a much lower level.
Meter’s sampling rate
This is, most possibly, the most important characteristic of an RF meter, even more, important than it’s accuracy. An RF meter with a slow sampling rate (2/sec) will not be able to catch, measure and show the high peaks of short RF transmissions, even if it will be set up to show peak levels. In the digital RF world signals are changing in a nSec, uSec, mSec level. WIFI, DECT, UMTS, BLUETOOTH, CDMA, pulse radar, even cell tower and many other modern digital signals are based on many, very short (mSec, uSec, nSec) pulses. A slow meter will not be able to “see” the fast signals. Just for reference, the CORNET ED78S, our recommended home-use EMF meter (1/2016) measures 3500 samples every half a second and shows the Max Peak and Average value.
A slow meter will show outcomes levels that are a fraction of the peak level (we believe that every peak and pulse influences the body). A slow meter that measures Average levels (as most professional testers do) will show even a lower level. Not all professional RF testers will use a fast RF meter that is able to measure the short high peak level correctly.
Meters sensitivity
When RF(Radio Frequencies) EMF (Electromagnetic Fields) radiation professional measurements are concerned there is grate impotency to the sensitivity of the meters. Most of the professional meters can scene RF levels of 0.1 uW/cm2 and up. EHS people, me included, feels pain and other symptoms at levels mush lower than 0.1 uW/cm2. What would the professional measurement results would worth to us or to people who are relay concerned with the health effect of RF EMF? Would you consider the level of 0.1 uW/cm2 safe?
I recommend that one of the first things you check with a professional EMF tester is how sensitive his RF meters are.
Measurement techniques and tests protocols.
The way the measurements and tests are performed is very important. In Israel, professional testers are obligated to test the radiation levels only at the high of one meter above the floor, and one meter from the walls. Such measurements do not take into account the possibility of an employee who decides to place his chair 1 feet away from the wall which is next to a power transformers room, or another case in which a worker sits on the chair at a height of 50 centimeters above the floor when below it there is a power transformer room.
What about the baby crawling on the floor with the in-floor electrical heating system? The baby will be exposed to much higher radiation levels than the levels that will be measured at a height of one meter from the floor by a licensed professional radiation tester.
Measuring several sources and multi frequencies
Both simple and professional RF radiation meters (for safety survey) are not cable to show the accumulated RF radiation over the frequency span and off all the sources combined. Most meters are capable to the show the RF EMF/EMR level in only a single frequency.
Most of the RF meters, even the more professional ones, are influance more from the strongest signal around, and mush less from other signals. In reality the radiation you are exposed to is the combination of all the signals across the frequency span. In addition in some meters the operator can configure the meter to test only small part of the frequency span, giving even a more partial outcome. In order to measure the RF correctly without the influence of this problem, you need to use a very fast (and expensive) speqtrum analyzer (60G/sec sampling rate, and higher), measure the levels across the span and combine them all.
RF measurement of several sources that are deployed around the meter is also problematic. As one vector of one of the sources can cancel one other vectors (fully or partially). For example, if you put 2 identical RF sources 2 meters apart, directed one to the other, and you put a human exactly in the middle between them, the person will get 2X the radiation of one source. While if you put a meter in between, the meter will most likely measure less than 1X of the RF radiation (depending of in/out phase of the transmission). The right way to measure this scenario would be to measure each source by it’s own, and then combine the levels. This is seldom done in the safety survey world.
Video presentation of this issue – https://youtu.be/VSm1nD-I6ZY
It is important to remember that in front of a cellphone mast, or in other test environments there are sometimes many sources of EMF/EMR in different frequencies, and the meter can usually measure only the highest level but can’t measure or calculate all.
Meter configuration and setup
In most professional EMF meters, it is possible to change the setup of the meter, so it will measure one or 3 axis, so it will measure only part of the frequency span, so it wil average the levels, so it will divide it’s sampling rate in a different way (over frequency or time span). All these changes can cause big changes in the measurement outcome.
In order to understand fully the measurement that was taken you need to read the full report of the test, or to take part in the tests. you need to pay close attention to the meters’ operation options and it’s selected configuration when the tests were done. You need to understand when and for how long the measurement was done. The to try an evaluate the effect of each factor over the outcome. Even then there is a lot of room for errors in the measurement process and configuration.
The Hours that the measurement is done at
Measurement results can be different at different times of the day. Low-frequency electromagnetic radiation levels, from the electric power network, will be higher during peak electricity consumption hours and will be lower when fewer people use the network. The same thing goes for radiation levels from the cellular network. When many people use cellular network services, for example, at noon, cellular antenna radiation will be very high, when at night it will be very low. Another example is that in day time all the street lights in the city are off but at night time they are on. In this case, low-frequency electromagnetic radiation from the power lines will be lower in the day time and higher in the night time. Day or night, Winter or summer, when residents in your neighborhood will use more electricity, for heating or air conditioning, the electromagnetic radiation from the electricity power lines will be higher. If the professional tester will visit you at noon he might measure very low radiation compared to radiation that will be measured in the evening peak time, in residential neighborhoods (18:00-21:00 weekdays for ELF). So, the hour that the test is done at has a real impact on the results of the measurements.
Controlling the radiation source.
Radiation sources can be shut down. If a cellular company knows about the measurement it can lower the transmission levels or shut down the antenna during the test. In this case, measured values will be very low compared with the actually existing values at most days when the antenna operates at full strength.
Another example is the shutdown of an entire high voltage line (electric company does it all the time to perform maintenance work on the lines or to control the power supply sources and consumption) during the measurement that will cause the measured levels to be very low compared to the daily situation when the line runs in full order.
Summing up, control over the radiation source can result in a significant change in the measurement results.
Safety meters calibration for RF
In Israel, the calibration test protocol is to test the meter accuracy during the measurement of only one RF signal at a time. This measurement is done for the following frequencies, again one by one:
650KHz, 1.2MHz, one frequency between 10MHz and 20MHZ, 80MHz, 200MHz, 400MHz, 800MHz, 1800MHz, 2400MHz, 7GHz, 18GHz, 23GHz.
The measurement is done in a lab condition for only one signal at the time, a signal which is constant. While the measurements in the field are done for many signals, most signals are multi frequencies and frequency hopping and that appear and disappear thousands of times in a second.
What good this calibration method is if it is so different then the condition in the field?
This calibration protocol allows professional meters that are not able to deal with fast-changing, multi-frequency, frequency hopping signals, created from multiple sources, to pass the test, but when they are used in the field, it is possible that they will show only a small amount of the RF radiation.