All aerobic and anaerobic life is adapted to survive in a narrow range of oxygen concentration. Oxygen is the terminal acceptor in oxidative phosphylation in mitochondria, the cell's ATP making powerhouse. Oxygen also regulates production of proteins involved in nitrogen fixation in anaerobes, and is required for inflammatory elimination of invading foreign substances such as virus and bacteria by production of reactive oxygen species (ROS). WPI's dissolved oxygen sensors are sensitive linear and enjoy a broad range of application.