Description of AS56-F / AS56-N sensors
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optek-sensors AS56, Version 04.2010_1.2US, 15.04.2010
www.optek.com
Attenuation of light intensity, as a result of absorption and/or scattering of
substances in the process medium, is described by the Lambert-Beer Law. It
states, the logarithm of the transmission loss is proportional to concentration of
the substance. This is true for dissolved substances and undissolved material.
Depending on the particular material properties, concentrations can be detected
in ppm as well as in %.
According to this law, the extinction coefficient, defined through ingredient and
wavelength, affects the logarithm of the transmission loss, too. Therefore, the
choice of wavelength or wavelength range is of decisive importance for the
measurement and is defined for each measurement type with the help of optical
filters.
The third factor of influence in the Lambert-Beer Law is the path length of light
passing through the process medium. Equally proportional, the path length, too,
is an important aspect with regard to specification of a photometer. The distance
to be covered by light is defined through the optical path length (OPL), that is the
distance between the windows in the measuring segment of the sensor. The
OPL of your sensor is given on its serial number plate.
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