Your formula for water analysis. There are only two dates you need to remember once a year - Your anniversary and calibration of your dissolved oxygen sensors The Hach Orbisphere K1100 dissolved oxygen sensor is virtually maintenance free. Unlike other oxygen sensors, the K1100 only requires one calibration and two minutes of maintenance per year. Watch the video to see just how fast it is. 800-227-4224 * www.hach.com/K1100 CIRCLE 2 ON READER SERVICE CARD Watch the video now at www.hach.com/K1100http://www.hach.com/K1100 http://www.hach.com/K1100