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 “cycles per second”. Most people are familiar with hertz from
radios--if an FM station advertises that people can find them at “97.9 on the
dial,” 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 “MAGNETIC 0-3 range)”
and the dial shows “1” on the middle scale, it is actually 0.01
milligauss. If it shows “0.6”, that
means 0.006 milligauss (which is also 6 micro gauss).
If
the knob is set at “MAGNETIC (0-100 range)” and the dial points to “4” 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 “stray voltage” or “stray
currents”. 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 isn’t. 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
doesn’t 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.
Ÿ
Computer, screen and
keyboard
Ÿ
Wrist watch
Ÿ
Electronic thermostat
and thermometer
Ÿ
Fluorescent light,
low-energy light
Ÿ
Microwave oven
Ÿ
Refrigerator, freezer,
Ÿ
Electric water heater
Ÿ
Cordless phone, mobile
phone
Ÿ
Outlets with GFI/GFCI
protection
Ÿ
Electric fence
Ÿ
Car, car electronics
Ÿ
Electric power lines
Ÿ
Night stand clock
Ÿ
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 “microwave oven
effect”. 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 “No Place to Hide” 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.