EM Field Measuring Review

Em Field Measuring Review


In our modern society, electricity is vital to our health, safety, comfort, and well-being. In today’s world, we are surrounded by high-tech gadgets and devices that transmit high-frequency waves, such as smartphones, iPads, iPhones, WI-FI routers, etc. All of them need electrical power. So, more and more electrical power stations, power transformers, electrical switch rooms are being built next to our neighborhood.  While our daily use of electricity is often taken for granted, public concern has arisen about potential adverse health effects from electric and magnetic – electromagnetic – fields (EMFs) produced by our use of electricity and all our ‘daily’ devices.

power towers

What is EMF and its Sources

Electromagnetic fields (EMFs) are invisible fields of electric and magnetic force associated with the movement of charged particles. EMFs are produced by natural sources, such as the movement of liquid magma below the earth’s crust as well as human-made sources, most often involving the production and distribution of electricity. EMFs also arise from the operation of electronic equipment and appliances in our homes and businesses such as computers, televisions, and refrigerators.

EMFs are comprised of both electric and magnetic fields. In electric power systems, voltage, defined as the force that causes electrons to flow in a wire or cable, produces electric fields. The strength of an electrical field is measured in units of volts per meter (V/m). Current produces magnetic fields (defined as the rate at which electrons flow across a conductor). The strength of a magnetic field is typically measured in units of tesla (T), gauss (G), or milligauss (mG). One milligauss is 1/1,000th of a gauss and one gauss is 1/10,000th of a tesla.

To illustrate (see pic. below), the cord of a lamp plugged into a wall socket but turned off will generate an electrical field from the voltage in the line. When the lamp is turned on, electrical current flows through the cord creating a magnetic field in addition to the electrical field.

Electric and Magnetic Fields

Both fields are invisible and perfectly silent.

The Electromagnetic Spectrum

The electromagnetic (EM) spectrum is the scientific name for types of photon radiation. Radiation is the energy that travels and radiates out as it moves. Electromagnetic radiation consists of photons (light particles) that travel in a wave-like pattern at the speed of light.

The amount of energy found in these photons forms various types of electromagnetic radiation in the spectrum expressed in terms of energy, wavelength, or frequency.

Frequency is measured in cycles per second (which is called a Hertz), the wavelength is measured in meters, and energy is measured in electron volts. The strength of an EMF depends on its wavelength and frequency. A greater number of waves with shorter wavelengths create more energy as you move up the spectrum.

EMF spectrum

What EMF Level is Safe?

There’s a heated debate as to what ElectroMagnetic Field (EMF) Level is considered safe. Since the experts have not come to a consensus, you’ll have to decide for yourself… Many government and utility documents report the usual ambient level of the 60-Hz magnetic field to be 0.5 mG.

Thus, any EMF detector reading higher than 0.5 mG is above the “usual” ambient exposure. Many experts and public officials, as well as the few governments that have made an effort to offer public protection, have adopted the 3 mG cut-off point. The EPA has proposed a safety standard of 1 mG. Sweden has set a maximum safety limit of 1 mG.

In everyday life, most people do not experience magnetic fields that exceed guidelines for acute exposure.

The table below shows the magnetic field strength of some common appliances and electronics. At a distance of three to five feet, the strength of the magnetic fields generated by most household appliances is indistinguishable from the typical amount a person might encounter even if the source was not present.



Field strength at 12 inches (milligauss)

Field strength at 12 inches (milligauss)

Coffee Maker

0.09 to 7.3

0 to 0.61

Copy machine

0.05 - 18.38

0 - 2.39


1.8 - 12.99

0.07 - 1.11

Vacuum Cleaner

7.06 - 22.62

0.51 - 1.28

Microwave oven

0.59 - 54.33

0.11 - 4.66

Computer monitor

0.2 - 134.7

0.01 - 9.37


How to Detect and Measure the EMF Level?

Since EMF is invisible, the only way is to measure its level is using an EMF Tester (or EMF Meter). An EMF Meter is a scientific instrument for measuring electromagnetic fields.

EMF Meters

There are many different types of EMF detectors/meters, but the two largest categories are single-axis and tri-axis. Single-axis meters are cheaper than tri-axis devices but take longer to complete a survey because the meter only measures one dimension of the field. Single-axis instruments have to be tilted and turned on all three axes to obtain a full measurement. A tri-axis meter measures all three axes simultaneously, but these models tend to be more expensive.

For in-house use, it is also possible to find such types of EMF meters as Radiofrequency (RF) Meter and Microwave Oven Leakage Meter.

Tri-axis vs Single-axis

Single Axis or Triple Axis also know as Trifield or 3-Axis. The single-axis EMF meter is a very direction meter when it comes to measuring EM fields. This means you have to be pointed at the EM field with the sensor to get a valid reading. If you are off axis or pointed away from the EM field, your readings will be very low or inaccurate and often non-existent.

The Trifield or 3-axis EMF meter allows you to measure the EM field in 3 dimensions. This means it will detect EM fields from all angles so there is no need to angle the device towards the EM field you are trying to measure. EMF meters of this type are better equipped to read broad types of EM fields and also assist in determining overall levels of EMF exposure.

Single-axis EMF meter is popular with many ghost hunters, it is also used in the RF and electronics industry to measure EM fields for potentially high exposure levels of EMF. Keep in mind that single-axis meters are a very directional EMF detector meaning that you have to point the unit directly at the EM source to get an accurate reading.

Tips on Measuring EMF

The levels of EMF may change over time when measuring EMF from the outside. Try to measure at different times of the day, and on both weekdays and weekends.

Some EMFs are 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.

Radio-frequency radiation can vary dramatically within minutes in areas with many sources, such as cell phones and wireless networks. This can be seen in areas with many shops, apartments, etc.

A common mistake is to walk around with an RF meter and think that certain spots are “hot”, when it is just the ambient level that temporarily peaked. Before considering a spot “hot”, make sure to really verify that with multiple readings, especially if there are no close-by sources.

Some equipment will broadcast on many frequencies. One example is a hair dryer: the heating element will emit EMF on 50 or 60 Hz, while the blower motor will broadcast across many frequencies. Another example is a compact fluorescent (CFL) light bulb.

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