Optek TF16 Instruction Manual page 10

Description of TF16 / TF16-N sensors
Due to the small scattering angle, direct light and scattered light practically travel
the same distance in the process medium. This is why product specific
disturbances such as color or color changes of the carrier medium as well as
soilings on windows may be optimally compensated.
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optek-Manual--1004-2006-02--TF16-US-2011-06-20
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