The Hanna High Scale Phosphate Checker® represents a good compromise between the choice of simple chemical test kits and professional instrumentation. Chemical test kits have limited accuracy and resolution as they are based on the distinction of color differences perceived by the human eye. The professional-grade instrumentation integrates a light source consisting of an LED or tungsten lamp with a filter and a light detector to accurately determine the absorbance and concentration of ions. Professional tools offer higher resolution and accuracy, but can cost hundreds of dollars. The Hanna High Scale Phosphate Checker® uses a fixed wavelength LED source and a silicon photocell to ensure the accuracy of professional instrumentation at the affordable price of a chemical test kit.