PPM Sensor for CHLORINE level measurement CHEMTROL® is introducing a new line of PPM sensors for direct measurement of CHLORINE measurement in water in parts per million (ppm) or milligrams per litre (mg/l). Unlike other chlorine sensors on the market, our solid state sensor features superior precision and control of free chlorine levels, with industry-leading reliability and low maintenance requirements. These sensors are very precise and so reliable that they are covered by a 2-year warranty. They are easy to install and practically maintenance free. The PPM sensor can be used alone or in combination with an ORP sensor to give the operator complete control of water quality. New membrane-less sensors are also available for Chlorine Salt Generators.