Water exhibits a strong absorption characteristic of some specific wavelengths of infrared light, and its infrared absorption spectrum is shown below. When using these specific wavelengths of infrared radiation materials, the water will absorb some of the infrared energy contained in the material, the more the more moisture absorption, so as to reduce the amount of reflected light measurement calculation of material moisture.
        Because the material of infrared reflectance due to the different absorption characteristics and spurious features vary, if only the water absorption wavelength, surface state, color, structure and other factors can interfere with material moisture measurement; the three wavelength method, namely a strong water absorption wavelength (wavelength) and two is absorbed by the water not too strong (wavelength reference wavelength), detection and calculation of the three wavelength of reflected light energy ratio, can eliminate the interference of other factors on measuring moisture.
        The working principle of the OMM3001 moisture meter is shown in the following drawing. The infrared light emitted through the points on the disc filter, through the mirror on the detected material; different filters on the disc points only allow a certain wavelength of infrared light, divided in motor driven disc rotating speed, the measuring wavelength and reference wavelength of the infrared light into alternately measured material; the infrared part is the material absorption, reflection to the concave mirror by the photoelectric sensor is received and converted into electrical signals by subsequent circuits to calculate material moisture.