HI97771 is an advanced portable photometer for the measurement of free and ultra high range total chlorine in water. This meter offers a superior optical system that utilizes a reference detector and narrow band interference filters for extremely fast and repeatable measurement. Chlorine is a common chemical used by for disinfection. High levels of chlorine, whether in liquid or produced by electrolysis of salt, is used in a variety of industries including produce washing, food processing, and the disinfection of medical equipment due to its' effectiveness as a biocide. The 2017 FDA Food Code 4-501.114 states that based on temperature the chlorine concentration of equipment wash water should be between 25 and 100 mg/L. HI97771 is designed to measure very high concentrations, 500 mg/L (ppm), of total chlorine in water. This meter also has a free chlorine range and can measure up to 5.00 mg/L (ppm). The HI97771 has an innovative optical system that offers superior performance in accuracy, repeatability, and the short amount of time it takes to perform a measurement. This compact, waterproof meter is extremely user friendly with a tutorial mode that walks the user graphically, step by step, in performing a measurement. The use of a backlit dot matrix LED allows the use of virtual keys which makes the operation of the meter very intuitive including selecting different methods, reviewing GLP data, recalling the last 50 measurements, and customizing the meter to user preferences. HI97771 is completely waterproof including the cuvette holder that is designed with ridges to protect the optical path from getting scratched by the cuvette and a gasketed battery compartment that holds three common AA batteries. The compact design fits comfortable in the hand for use in the field or on a table for benchtop use. The LCD is 71 mm (2.75") by 37 mm (1.6") and is backlit for easy viewing under all conditions.