Microwave is a generic name for an electromagnetic wave with a relatively long wavelength from 1cm to 1m.
Microwaves travels in a straight line in the space, however, it is reflected on a metal surface and the energy is transmitted through decaying electrically-insulated dielectric substance. For example, water is composed of positive ions and negative electrons in pairs, and pairs of ions and electrons rotate toward the electric field when microwave is radiated at them as shown in Figure 1 (a). When the electric field is reversed as shown in Figure 1 (b), the pairs of ions and electrons rotate to reverse arrays. Energy lost due to this rotation is microwave attenuation. Therefore, the molar mass to be rotated increases when moisture content increases, and attenuation also increases. Water is known as a high dielectric substance among dielectric substances. Our microwave transmission type moisture meter applies this principle and measures moisture by radiating microwaves at the measurement object and measuring the energy amount before and after transmission.