The Kemtrak DCP007NIR uses fiber optics to shine a precisely focused monochromatic (single wavelength) light beam through the process medium and back to a silicon photo-detector.

The attenuation of the transmitted light beam caused by light absorbing substances in the process medium is mathematically described by the Beer-Lambert law.

Applying the Beer-Lambert law (below), the concentration of the sample can be calculated.

A = ε l c

where:

A = absorbance (= - log transmittance)

ε = molar absorption coefficient

L  = optical path length

C = concentration of absorbing species

DCP007 Photometer measurement principle