The molecular structure, such as the hydrogen oxygen bond in water, absorbs near-infrared light of a specific wavelength (specific measurement band 1940nm). At a specific wavelength, the reflected near-infrared energy is inversely proportional to the near-infrared energy absorbed by water molecules in the material. The moisture content of the tested material can be calculated based on the amount of energy loss.
Water molecules are not stationary: they vibrate when encountering specific energy bands. The bond that binds two hydrogen atoms and an oxygen atom in a water molecule can stretch, contract, or twist in other forms. External energy is needed to induce these vibrations. The required energy covers specific bands throughout the entire electromagnetic spectrum. In different parts of the entire spectrum, there are some absorption bands that are very strong and some that are very weak. In the near-infrared region of the spectrum, this band is particularly strong for water molecules, and the instrument is easy to achieve in terms of emitting, filtering, and receiving energy.
Near infrared measurement technology is a non-destructive, non-contact real-time measurement technique.