Whiteness Meter NWNM-200 adopted with the principle of photoelectric effect for measurement and whiteness calculation formula of the instrument is blue light whiteness R457. Built in with optical system, display system, detection system, data process and light source. Optical cell received the diffuse reflectance radiant brightness energy value of the sample surface. High-precision auto zeroing operation amplifier, amplified the value of sample surface and for energy calibration it inputs to the calibration circuit. The whiteness value of the sample is directly shown on the display. It is used to measure the whiteness value of powder or object with a flat surface.