Photometer provides economical field spot testing, as well as fixed sensor calibration support for measuring free chlorine and chlorine dioxide. The environmentally friendly and highly accurate instrument is EPA-compliant for regulatory testing and carries the CE mark. A 525 nm LED light source is used to deliver high accuracy measurement of free chlorine from 0-11 ppm or chlorine dioxide at 0-6.5 ppm with photometric precision of ± 0.1/0.01%T and transmission range of 100-0.00%T. The chlorine dioxide sensor offers real-time measurement with an advanced amperometric sensor. It is available in both 0-2 ppm and 0-10 ppm measurement ranges.