3
The characteristic of electromagnetic fields :
Electromagnetic fields propagate as waves and travel at the speed of
light (c). The wavelength is proportional to the frequency.
λ
(wavelength) =
c (speed of light)
f (frequency)
If the distance to the field source is less than three wavelength, then
we are usually in the near-field. If the distance is more than three
wave length, the far-field conditions usually hold.
In the near-field, the ratio of electric field strength (E) and magnetic
field strength (H) is not constant, so we have to measure each
separately.
In the far-field, however, it is enough to just measure one field quantity,
then the other could be computed accordingly.
2-2 Application
Quite often routine operation, maintenance and service work has to be
done in areas where active electromagnetic fields are present, e.g. in
broadcasting stations, etc. Additionally, other employees may be
exposed to electromagnetic radiation. In such cases, it is essential that
personnel are not exposed to dangerous levels of electromagnetic
radiation, such as:
High frequency (RF) electromagnetic wave field strength
measurement.
Mobil phone base station antenna radiation power density
measurement.
Wireless communication applications (CW, TDMA, GSM, DECT).
RF power measurement for transmitters.
Wireless LAN (Wi-Fi) detection, installation.
Spy camera, wireless bug finder.
Cellular/Cordless phone radiation safety level.
Microwave oven leakage detection.
Personal living environment EMF safety.
