Abstract: An optical sensor is provided with an adjustable and variable optical path length (OPL). The optical sensor can be used in conjunction with a flow cell for ultraviolet (UV) absorbance measurements. On opposite sides of the flow cell, optical windows are installed in cylindrical window holders and held in place by window retainers. The distance between opposing faces of the optical windows defines the OPL. A fine pitch, close tolerance thread is machined on the outside of the window holders. This thread mates with a thread machined on an inside wall of a mounting ring. Rotation of the window holder and attached optics housing extends or retracts the window and window holder assembly, thereby providing the variable OPL. The OPL can be ascertained by examining external visual linear and/or rotational indicators on the sensor device.

Abstract: A system and method for measurement and control of suspended solids in a fluid includes a sensor, dosage supervisor and logic module. The sensor includes a measurement chamber with a piston. A diverter valve controls introduction of sample fluid into the measurement chamber in coordination with position of the piston. A measurement cycle includes the diverter valve allowing sample fluid into the measurement chamber as the piston retracts from the measurement chamber. The diverter valve prevents sample fluid from leaving the measurement chamber as the piston extends into the measurement chamber to compress the sample fluid. After a certain time of compression, light is transmitted across a portion of the sample fluid. The light received by a light detector is used as a measurement of suspended solids concentration in the fluid. This measurement is used to control introduction of polymers into a fluid source.