For in-line real-time process monitoring and for accurate measurement of color or color changes, optek-Danulat Inc. has released the model AF26 dual-channel absorption sensor. It uses light in the range from 385 to 1100 nm at selected wavelengths. A precisely defined, constant light beam penetrates the process medium, is divided by a beamsplitter and passes through the interference filters at application-dependent wavelengths. Two hermetically sealed silicon photodiodes detect the attenuation of the light intensity and compensate for turbidity in the process streams. The optical window is made from a single crystal sapphire, providing resistance to abrasive and corrosive media. Line sizes range from 1/4 to 8 in., optical path length is from 1 to 1000 mm, and operating temperature is from 0 to 40 °C.