The Rosemount FCL Free Chlorine Measuring System measures free chlorine in fresh water. The free chlorine system includes a transmitter (Rosemount 56 Transmitter or Rosemount 1056 Transmitter), a Rosemount 499ACL Free Chlorine Sensor, a pH sensor (if required) and a constant head flow controller. The transmitter and flow controller are mounted on a back plate, and quick disconnect Variopol (VP) sensor cables are pre-wired to the transmitter, making installation and startup fast and easy.