How is RF radiation measured?
RF waves and RF fields have both electrical and magnetic components. It is often convenient to express the strength of the RF field in terms of each component. For example, the unit “volts per meter” (V/m) is used to measure the electric field strength, and the unit “amperes per meter” (A/m) is used to express the magnetic field strength. Another common way to characterize an RF field is by means of the power density. Power density is defined as power per unit area. For example, power density can be expressed in terms of milliwatts (one thousandth of a watt) per square centimeter (mW/cm2) or microwatts (one millionth of a watt) per square centimeter (µW/cm2). The quantity used to measure how much RF radiation is actually absorbed by the body is called the Specific Absorption Rate or SAR. The SAR is a measure of the rate of absorption of RF radiation. It is usually expressed in units of watts per kilogram (W/kg) or milliwatts per gram (mW/g).
