The FDO is a luminescence-based, optical DO sensor for the IQ SensorNet process monitoring system. The FDO is a reliable, proven, long-term solution for continuous DO monitoring that can help optimize your aeration system and lower energy costs. Replaceable sensor cap provides a longer life and simple maintenance. A standard sensor cap (SC-FDO 700) is provided for typical applications. A fast response cap (SC-FDO 701) is available for highly dynamic environments.