Free Chlorine Measurement (Cl)

Cl 911 Free Chlorine Probe

Measuring cell for free chlorine with replaceable membrane caps.


  • Short response time
  • Minimal maintenance
  • Temperature compensation
  • No reagents required
  • Robust design
  • Environmentally stable
  • Easy to install

The sensor head of the Cl 911 contains a noble metal electrode covered by a gas-permeable membrane. During measurement chlorine in the sample passes through the membrane and reaches the electrode, where it is reduced in an electrochemical reaction. This reaction generates a current which is proportional to the concentration of chlorine in the sample. A sufficient flow rate (minimum 15 cm/s) is required for the measurement. We recommend to use a flow cell (available accessory).

Measured parameter and interferences: The probe detects free chlorine from hypochlorite, gaseous chlorine or generated by electrolysis. The sample water must be free of surfactants. Chlorine dioxide and ozone are detected as well.

  • Drinking water
  • Pool water
  • Process water
  • Cooling water
  • Chlorination of wastewater