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ABB AW400 Series Residual Chlorine Monitor

AW400 Series
KC Controls HB series Ball Valves  AW400 Series Data Sheet

Residual chlorine is one of the most important measurements for the effective monitoring of cooling, potable and industrial water treatment processes. ABB's new Residual Chlorine Monitor AW401 incorporates the features our customers need to monitor and control residual chlorine levels accurately and affordably. The design enables users to either connect up to three residual chlorine monitoring sensors to the system or to combine pH, ORP and residual chlorine sensors, thus reducing the cost of each measurement considerably.

  • Total and Free Residual Chlorine Measurement
    add potassium iodide to reagent to convert free chlorine measurement to total chlorine
  • Reagentless Operation
    reduced operating costs with reagentless operation at a pH of 7.5 or less
  • Multiple Sensor Input Capability
    reduced installation costs for multiple point monitoring operations
  • Self Cleaning Sensor Assembly
    prolongs sensor life and maintains accuracy

The AW400 is compatible with ABB's 17XX pH and ORP sensors and can be equipped with PID control for feed- forward dosing applications. Consumable parts are limited to the occasional addition of corundum sand and, rarely, the replacement of the copper anode. When it comes to meeting our customer's demands for accurate, affordable residual chlorine measurement, ABB's AW400 exceeds expectations.

Measurement Principle

The sensor is an amperometric cell comprising two concentric electrodes; an inner, spiral, gold measuring electrode and an outer copper cylinder – the 'counter-electrode'. Sample water flows into the electrode chamber through nozzles located in the measuring cell. The cell also contains a small amount of a special corundum sand that is circulated by the water and acts as an abrasive on the electrodes, keeping them at peak sensitivity. The AW400 measuring cell is polarized because of the normal reactivates (potential) of these two different metal electrodes in water. When oxidizing substances such as chlorine, bromine, iodine or their derivatives are present in the sample between the electrodes, the measuring (gold) electrode is depolarized and the counter electrode (copper electrode)dissolves as Cu++. This electron flow generates a signal (current), that is proportional to the oxidizing agent concentration in the sample. The signal is compensated for temperature variations via software in the AW400 transmitter through a PT100 thermistor.


Here are just a few of the common residual chlorine level monitoring applications for which the AW400 is ideally suited:

  • Drinking water
  • Cooling water for power stations and industrial facilities
  • Fruit and vegetable disinfection baths
  • Tertiary treated waste water
  • Swimming pools and spas

The choice is yours, you choose the disinfectant... we'll measure it! Regardless of the disinfectant used at your site, Chlorine, Chlorine Dioxide, Bromine or Ozone, the ABB AW400 is ready for use; simply select the disinfectant from the user-menu on the monitor.

For more information click on the pdf image above for full specifications, call KC Controls on 01293 538940 or send us an e-mail to