This sensor is designed to provide an accurate free chlorine reading without any of the negative limitations of traditional membrane sensors. This new technology works well in the presence of stabilizers such as cyanuric acid. These can be supplied with your controller or added at a later date. Like all free chlorine sensors, the reading supplied by the CP-1 sensor is flow dependant, therefore it requires a dedicated flow cell. The replacement CP-1 sensor comes with a package of glass cleaning beads.