Several molecular bonds absorb near infrared light at well defined wavelengths. The common bonds are O-H in water, C-H in organics & oils and N-H in proteins. The absorbance level at these specific wavelengths is proportional to the quantity of that constituent in the material.

Narrow band pass filters within the Transmitter create a sequence of light pulses. At least one of these pulses is at the absorbance wavelength specific to the constituent to be measured. The other pulses are created at wavelengths not absorbed by the measured constituent. The pulses illuminate the product and the diffuse reflected light is collected and focused onto a single, temperature controlled detector.

The electrical signals generated by the detector are then processed to provide a value that is proportional to the concentration of the measured constituent. The value is then displayed in % or other engineering units.