CRONOS HaloSense

The HaloSense range of monitors are used in many applications requiring the measurement and control of online residual chlorine levels. The HaloSense analyzers are suitable for chlorine monitoring or control applications in potable water, seawater, process water, swimming pool water, waste water, etc.

The following are available in the HaloSense range of chlorine analyzers:

  • Online total chlorine analyzer
  • Online free chlorine analyzer
  • Chlorine in seawater meters
  • Online zero chlorine meter (designed to measure the absence of free chlorine)

A range of residual chlorine analyzers using the HaloSense range means that you get exactly what you need and nothing that you don’t. From a low cost no-frills chlorine dosing controller (CRONOS) to a color touch screen, remote access controller (CRIUS) – and all with the same great sensors! The CRATOS HaloSense Analyser is now available with up to 12 sensor inputs, reducing the cost per point. Chlorine dosing control is now simpler and cheaper than ever!

Principle of Operation

Dr Reiss chlorine sensor tipThe membraned amperometric chlorine sensor is enhanced with a third, reference, electrode which eliminates zero drift. pH correction is often not required at all. (NB. These chlorine sensors are often known as polarographic chlorine sensors although this is a misuse of the word polarographic). Its unique design means that pH correction is not usually required at all, completely eliminating reagents.

In addition to the state of the art potentiostatic chrono-amperometric sensors, the HaloSense range of residual chlorine monitors has all the functionality that you need, and more. Simply choose the CRONOS, CRIUS or CRATOS controller to give you the highest quality, with all the functionality you need at the lowest price possible. This means that you pay for everything that you need and nothing you don’t, without sacrificing the quality of measurement!

The sensors used by the HaloSense monitors are largely pH independent meaning that the measurements are bufferless and reagentless. They are amperometric chlorine sensors and show remarkable sensitivity and stability. For those making a chlorine measurement at high pH (>pH 8.5) on variable pH water it is possible to provide pH compensation from either a pH sensor connected to the analyzer or from an external pH meter.

The sensors work by separating the electrodes that perform the measurement from the sample, by a membrane. This membrane allows the free residual chlorine (HOCl and OCl-) or the total residual chlorine (HOCl and OCl- plus chloramines) through the membrane. Inside the sensor the dissolved chlorine meets the electrolyte which is at a low pH. This converts the majority of the OCl- to HOCl. The HOCl is reduced at the gold working electrode and the current generated is proportional to the free chlorine or total chlorine present, and the instrument gives a reading in ppm or mg/l.

This technique is the most advanced method of continuous measurement and has many benefits to the user including a very stable online chlorine measurement and better dosing control.

The HaloSense Analyzers are bufferless and reagent free, meaning they have a low total cost of ownership and with maintenance intervals at 3 or even 6 months, the HaloSense bufferless chlorine monitor is fast becoming the instrument of choice for the engineer who wants the best analyser at the best price.

The CRONOS, CRIUS and CRATOS free and total residual chlorine dosing controllers are equipped with process control options, data-logging, relay outputs, serial communications, Ethernet, Modbus, HART, Profibus. Remote Access of the chlorine monitors (including remote access to all control options) is available via the internet over GPRS and via a LAN. In fact the CRIUS HaloSense monitors have all the options you could want, whilst the CRONOS maintains a low cost and is particularly great value for money!

  • Low purchase cost
  • Low cost of ownership
  • Reduced pH dependency (largely pH independent)
  • Stable and reliable
  • Free chlorine monitor
  • Total chlorine monitor
  • Combined chlorine monitor
  • Bufferless chlorine monitor
  • Reagentless chlorine monitor
  • Reduced pH dependency free chlorine sensor

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  • Continuous chlorine monitoring
  • Water treatment plant residual chlorine dosing control
  • Secondary chlorination free chlorine dosing control
  • Distribution monitoring
  • Cooling tower monitoring and control
  • Pasteurizer dosing control
  • Seawater chlorination control
  • Chlorine monitoring in seawater

Anywhere you have a requirement to measure residual free or total chlorine is a suitable application for the HaloSense. The HaloSense analyzer range is particularly suited to working in sites where reliability and ease of use are most important.


The HaloSense range can come equipped to automatically clean themselves at user defined intervals, with all the benefits of no operator intervention for up to 6 months. The autoflush is particularly useful in food preparation, pulp and paper, and many applications where there is likely to be a build up of solids in the sample. For more information about autoflush click here.

Chlorine Analyser Self Cleans

pH Compensation

For some applications with high and variable pH, pH compensation can improve the accuracy of the continuous free chlorine analyzer. For pH compensation to be valid it must be done with the highest quality pH sensors and with chlorine sensors that have a reduced susceptibility to varying pH, such as those used in the HaloSense range of online residual free chlorine analyzers.