The Hanna Total Chlorine Checker® bridges the gap between simple chemical testing kits and professional instruments. Chemical testing kits have limited accuracy and analysis, as they rely on human vision to discern color differences. Professional instruments incorporate a light source, such as an LED or tungsten bulb, with a filter and light detector to accurately determine ion concentrations. Professional instruments offer greater analysis and accuracy but can cost hundreds of dollars. The Hanna Total Chlorine Checker® uses a defined LED light type and a photodiode sensor to provide the accuracy of professional instruments at an affordable price of a chemical testing kit.