Waterproof Photometer 7500 includes adaptable tube holder and USB port for PC connection. Up to 500 results can be stored and downloaded for trend monitoring and report production. Built around water test reagents that use light to measure color change in water samples, model is accurate to ±0.005 at 0.3 absorbency units with resolution of 0.001 absorbency units. Sealed to IP67, photometer runs on AA batteries, USB port from computer, or adapter.