How to
Measure EMF
by
Andrew Eriksen, MS
Instruments
for measuring electromagnetic fields (EMFs)
Left to Right: upgraded Trifield gaussmeter, AM radio, HF
Detektor
Electromagnetic fields (EMF) are invisible, but exist everywhere
on Earth. To find them, we use
instruments.
There are many types of EMF and no single instrument can measure
them all. This article explains
what frequencies are and presents three low-cost instruments, each of which
measures some forms of EMF. It is
necessary to use all three types of instruments to get a more complete picture
of the EMF in a particular place.
After that, the question of how much EMF is acceptable is looked into,
together with where to check for EMF.
Frequency ranges
EMF radiation is mainly characterized by its frequency and its
strength. [1]
The frequency is measured in the unit hertz, which means Òcycles per secondÓ. Most people are familiar with hertz from radios--if an FM
station advertises that people can find them at Ò97.9 on the dial,Ó that means
they broadcast on the frequency of 97.9 mega hertz (or 97,900,000 hertz). The EMF transmitted by this station is
received by radios and turned into music and speech. However, an FM radio is not good at telling us how strong
the signal is, or what goes on across the dial at the same time.
An electrical wire in a house also broadcasts a signal, though
much weaker than a radio station.
Here it sends out the frequency 60 hertz (50 hertz in some countries),
which an FM radio cannot pick up, but a gauss meter can. The gauss meter, in turn, is completely
blind to a radio signal, or to most of the radiation coming from a computer,
for instance.
All sorts of electronic devices broadcast at different
frequencies; most do it on many frequencies at the same time.
For a person who is sensitive to EMF, it is important to know the
full picture if trying to minimize exposures to EMF.
The figure on page three gives an overview of the frequency
bands, and roughly which of them are measurable by which instrument. In practice, there is some overlap.
The gauss meter
The gauss meter measures the strength of the low-frequency EMF
radiation, like that coming from electrical wires (50 or 60 hertz). The better models can also show some
higher frequencies (thousands of hertz, kilo hertz), which come from some
electronic appliances, such as power supplies.
In North America, a gauss meter measures the strength of the
radiation in the unit milligauss. In other countries,
microtesla is used. (1 microtesla
= 10 milligauss).
Cheaper gauss meters are usually only able to show EMF levels
down to about one milligauss (0.1 microtesla). That is barely acceptable for healthy
people, and inadequate for people sensitive to EMF. People who are sensitive to
EMF are often affected by levels below 0.1 milligauss,
sometimes even below 0.01 milligauss (0.001 microtesla, 1 nanotesla).
Figure 1: Frequency
bands and frequency ranges measured by three different instruments.
A good cost-effective gaussmeter is the
TriField meter from Alpha Labs, which is available
from several mail-order sources, such as NEEDS and Less EMF (see vendor list).
The TriField meter can measure down to
0.2 milligauss and does not contain any digital
electronics, so it is tolerable to use, even by the most sensitive people. It has three built-in sensors, so it
automatically measures in all three dimensions. Most cheaper models have only one
sensor and must be turned around to find the highest reading. This instrument can also measure electrical
fields and radio waves, but it is not sensitive enough on those settings to be
of any value.
For a general survey of an area, simply walk around with the
meter in hand and notice what the levels are.
Areas where much time is spent, such as the bed, the favorite
chair and the dining and computer areas should be checked more thoroughly. In these places of longer exposure
times, it is important to check for EMF where all the body parts will be, both
the feet, the head, and in between.
The field can be much stronger on the floor than higher up--either
because of wires under the floor, or perhaps from electronic equipment placed
on the floor.
The human body appears to pick up EMF in all body parts, but some
areas, such as the head, may be more sensitive.
Other places to check with a gauss meter are near the circuit
breakers and the electrical meter, space heaters, electric stoves and water
heater, and various electronic equipment--including those
little plug-in transformers.
And remember to check on the other side of the wall from an electrical
device. Finally, check the car
with the engine running, especially the dash board and
the foot well.
TriField meter with upgrade
By request from the community of electrically sensitive
people, Alpha Labs designed an upgrade to their TriField
meter, that makes it 100 times as sensitive. This allows it to measure down to 0.002
milligauss (2 microgauss,
0.2 nanotesla).
This upgrade is only available directly from Alpha Labs, which
also sells enhanced meters directly.
The upgrade costs about $70 and requires the meter to be mailed to Alpha
Labs. Call first (see below). There are no other meters available in
this price range with this level of sensitivity.
The upgraded TriField meter is shown in
the picture. The wand is an
external probe, which does the measuring when plugged in. When not plugged in, the meter works
with the standard sensitivity.
With the probe plugged in, the scale on the
meter must be divided by 100 when read. For instance, if the instrument knob is turned to ÒMAGNETIC 0-3
range)Ó and the dial shows Ò1Ó on the middle scale, it is actually 0.01 milligauss. If
it shows Ò0.6Ó, that means 0.006 milligauss (which is
also 6 micro gauss).
If the knob is set at ÒMAGNETIC (0-100 range)Ó and the dial
points to Ò4Ó on the top scale, that means the EMF level is 0.04 milligauss (or 40 micro gauss).
The external probe is a wand 11 inches long. To save money and space, it measures
only in one direction. To get an
accurate measurement, it is necessary to perform three measurements at each
location.
To measure with the wand, first place the wand horizontally and
read off the number, once the needle has stabilized. It may be best to remove your hands
from the wand, as any slight movement
affects the reading. Then turn the
wand ninety degrees in either direction and do another reading.
Finally, stand the wand vertically and do a third reading. The highest reading is the correct
measurement for this location.[2]
One of the things this very sensitive wand can pick up is ground currents, which is electricity which runs in the soil. Some people refer to ground currents as
Òstray voltageÓ or Òstray currentsÓ.
Ground currents typically come from grounding rods on electrical power
poles, transformers and in buildings.
They can be found hundreds of yards away from any human structure.
Large power lines can sometimes be picked up more than a mile
away, in very rural areas.
When measuring ground currents, the reading will be the same
whether the probe is lying on the ground, or is several feet above it. The EMF-level does not rapidly diminish
with distance, as it does with a point source.
The AM radio
To get an idea of what EMF lurks in the middle range of
frequencies, a simple AM radio can be used. It does not provide a reading on a dial, but instead it
allows one to hear EMF emissions from electronic equipment, electrical motors,
arcing wires, GFCI relays and much more, most of which a gauss meter cannot
pick up.
A cheap AM radio is best, as more sophisticated models have
circuitry to suppress static--and static is what we want to pick up. Radios with digital controls are
unlikely to be useful here. A
simple, cheap battery-powered hand held radio is a good choice. (I use a Radio Shack model 12-467,
which costs about $20.)
Simply turn on the radio and set the dial in an area where the
least amount of noise is heard, and where there is nothing received from any
station. In my area, the top and
bottom of the dial range works very well.
Then walk around and put the radio close to electrical outlets in the
wall, exposed wires, fluorescent lights, telephone cords, any electronic
equipment, GFCI-protected outlets in the bathroom and kitchen, and so forth.
The radio will only pick up static when it is close to the source
in most cases. Humans may be more sensitive than the radio and need to keep a
greater distance.
Try to move the station dial to another place and check around
again. Some
equipment may sound differently or
louder on a different setting.
If the speaker is put against a wall or some equipment, the sound
coming from it may be reflected back and sound louder than it is, so you may
think there is an EMF problem where there isnÕt. It is thus best to hold the radio so the speaker is pointed
towards you and away from the item being checked.
Metallic surfaces act like antennas. When the AM radio is held near a metallic surface, it may
pick up a far-away radio station.
When touching metal, crackles may be heard. This is normal and does not mean there is a problem. The metal doesnÕt somehow gather and
enhance the EMF that was already there; it merely reflects and channels
it.
Radio frequency meter
In the high-frequency bands we encounter a soup of EMF from near
and far. High frequency EMF
reaches further than low-frequency EMF. In our own homes, there may be cordless phones,
microwave oven, computers and wireless networks. Some of these emissions can also come in from neighboring
buildings. From afar, transmission
towers of many kinds contribute to the overall level of electro-smog.
Today, there are virtually no areas free from radio frequency
radiation. The question is only
how much there is.
A great number of instruments are available to warn us about
radio frequency EMF, from simple pocket-devices that beep when the level rises,
to instruments one can point towards a source and it will display what
frequencies are being transmitted on.
A compromise on cost and sensitivity that I myself use is the HF-Detektor from the German company Aaronia. It costs about $150 and is very
sensitive for the price. One has
to go to a very remote area for it not to pick up anything.
It is a little more complicated to use than the TriField gauss meter, so it is not for people who are
uncomfortable with any sort of electronics. It contains a microprocessor and is uncomfortable to handle
for some electro sensitives, but with experience, a
measurement can be done in 5 seconds.
The instrument comes in a stylish design, but it needs to be
redesigned, because the antenna breaks off easily and the output is hard to
read in sunlight.
Reading the manual is essential for being able to use this
instrument. It gives readings in
decibel, which can be converted into watt-per-square-meter, using a table. The unit milligauss
is meaningless for these frequencies.
Things to try
With these tools in hand, it is like being outfitted with a new set of ears. Here is a list of things to try to measure. When measuring, notice how the reading is higher close up, and how it diminishes rapidly with a little distance, and notice how the different instruments react.
á Computer,
screen and keyboard
á Wrist
watch
á Electronic
thermostat and thermometer
á Fluorescent
light, low-energy light
á Microwave
oven
á Refrigerator,
freezer,
á Electric
water heater
á Cordless
phone, mobile phone
á Outlets
with GFI/GFCI protection
á Electric
fence
á Car,
car electronics
á Electric
power lines
á Night
stand clock
á Wireless
network equipment
Tips on measuring EMF
The levels of EMF may change over time, when measuring power
lines or the ambient level. Try to
measure on different times of the day, and on both weekdays and weekends.
Some EMF is seasonal.
A big power line may give a much higher reading on hot summer
afternoons, when everybody runs their air
conditioners. Or, the neighbors
next door may only generate EMF when they are home and doing certain
things.
Some equipment will broadcast on many frequencies. One example is a hairdryer: the heating element will emit EMF on 50
or 60 hertz, while the blower motor will broadcast across many
frequencies.
A computer consists of many parts inside the box and the
screen. All parts may generate a
multitude of frequencies. There
will be a number of transformers inside, which generate the different voltages
needed by various parts in the computer.
Each transformer emits EMF in the low kilo hertz
range. The processor chip itself
will emit EMF around a few gigahertz (the advertised
speed is the frequency of the processor).
There are many other components inside the computer case, such as disk
controller, network card, etc., which will run (and thus emit EMF) in the
megahertz range.
The screen and the cable going to it will have their own set of
emitted frequencies.
It is actually possible to tune in to a computer, using special
equipment. It is then possible to
read what is on the screen, right through walls of a building. Intelligence agencies and spies have
used this method for decades.
How much EMF is too much?
What levels of EMF are acceptable? That is a good question, with no firm answers. Nobody knows for sure, and it also
depends on whether it is continuous exposure--perhaps round the clock--or just
for shorter periods of time, like in a car. Some people also think that exposures during sleep should be
lower than what is acceptable during the day. And then it also depends on whether the person is healthy or
electrically hypersensitive.
The official standards for how much EMF radiation is allowed are
in the United States based solely on the heating effect on body tissues--the
Òmicrowave oven effectÓ. Any other
effects were completely unknown when the standard was set decades ago. Most other countries then simply copied
the US standard. All these
standards are nearly worthless.
Among health practitioners and some researchers, there is an
unofficial consensus that low-frequency EMF should be kept under the 1-4 milligauss range.
This is for ongoing exposures for a healthy person.
For people who are hypersensitive to EMF, the 1-to-4 milligauss range is not low enough. It is up to the individual to find out
what is. Some people do fine with
0.1 milligauss, some need less than 0.01 milligauss.
For the middle frequencies--those picked up by an AM radio--the
best advice is to avoid places where any static is picked up--especially for
the sleeping area.
For radio frequencies, the standards are all over the place, and
are again based
on the heating effect of body tissues.
These standards are published in the unit watt-per-square-meter (W/m2)
or microwatt-per-square-centimeter (uW/cm2, 100 uW/cm2 = 1 W/m2). A list of the
standards for several countries are published in the June 2002 issue of
the ÒNo Place to HideÓ journal (no longer published).
Most countries, including Australia, Canada, Japan, the United
States and most of Europe have standards limiting the radiation to 2 to 10 W/m2
(200 to 1000 uW/cm2). Great
Britain allows up to 100 W/m2. A
number of countries, like Russia, China and several European countries limit
the exposure to 0.1 W/m2. A few
local rules are much stricter. The
most strict is New South Wales, Australia, which only
allows 0.000,01 W/m2 (10 uW/m2).
New South Wales is the most populous state in Australia and includes the
Sydney metropolis. The New South
Wales standard is not as outlandish as it may seem; it is the other standards
that are outlandishly high.
Ambient levels of high-frequency EMF will rarely get near even
the New South Wales (NSW) standard, even in a big city. But being within a few feet of a
wireless network hub, or a roof-mounted cell-phone transmitter, probably
would. In the country, where the
cell-towers cover a larger area and thus have a higher
signal strength, this standard may be exceed when close to the tower.
There is no consensus on at what level people who are
hypersensitive to tower-emissions are safe. Some sensitive people suggest 1/10 of the NSW standard
(0.000,001 W/m2, 1 uW/m2), others prefer even lower.
Vendors
Alpha Labs
1280 South 300 West
Street
Salt Lake City, UT 84101
USA
Phone: 1-801-487-9492
Aaronia AG
D-54597 Euscheid
Germany
Less EMF Inc.
809 Madison Avenue
Albany, NY 12208
USA
Phone: 1-888-LESS-EMF / 1-518-432-1550
NEEDS
P.O. Box 580
E. Syracuse, NY 13057
USA
Phone: 1-800-634-1380
Copyright
© Andrew Eriksen, 2007.
Permission to copy and distribute this article is granted for
educational, non-commercial purposes.
________________
[1] Other characteristics include the shape of the signal (sinus wave, square
wave, irregular, etc.), whether it is continuous or pulsed, and many other
factors.
[2] The more precise number is the geometric sum of the three readings,
but such accuracy is not needed, and the instrument is not that accurate
anyway. If the three readings were
2,3, and 10, the more correct number is the square root of (2 x 2) + (3 x 3) +
(10 x 10) = 10.6.