Chlorine Analyzer for Residual Chlorine Monitoring – HaloSense

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• Continuous online monitoring for residual chlorine in any water
• Water treatment plant residual chlorine
  
• Secondary chlorination
  
• Distribution monitoring
• Cooling tower monitoring and control
• Pasteurizer dosing control
• Seawater chlorination
  
• Bromine monitoring in seawater
• Food washing and food container washing
  
• Chloramination control (MCA) in paper and pulp

The HaloSense chlorine monitor range is particularly suited to working in sites where reliability and ease of use are most important.

The following are available in the HaloSense range;

• Online free chlorine – 0.005-2ppm, 0.05-5ppm, 0.05-10ppm, 0.05-20ppm, 0.5-200ppm
• Online total chlorine – 0.005-0.5ppm, 0.005-2ppm, 0.05-5ppm, 0.05-10ppm, 0.05-20ppm
• Online residual chlorine in seawater analyzers (free or total bromine) – 0.005-2ppm, 0.05-5ppm, 0.05-10ppm, 0.05-20ppm
• Online zero chlorine (designed to measure the absence of free chlorine) – 0.005-2ppm for applications such as post activated carbon and pre-RO monitoring.

Other options include;

• AutoFlush – The HaloSense sensors 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
• Communications – The CRONOS^® and CRIUS^®4.0 free and total residual dosing controllers can be equipped with four PID process control options, data-logging, relay outputs, analog outputs and serial communications such as: Ethernet, Modbus and Profibus. Remote monitoring of the instruments (including remote access to all control options) is available via the internet over GPRS and via a LAN. In fact the CRIUS^®4.0 HaloSense monitor has all the options you could want, whilst the CRONOS^® provides a low cost alternative and is particularly great value for money!
• Control – Each Residual Chlorine Analyzer from Pi has the capability to be an extremely capable Chlorine Controller. The controllers can have multiple control channels which can utilize chemical control (usually a relay (switch) turns dosing on when the chlorine is too low or off when it is too high) or PID control. PID stands for Proportional Integrated Derivative and it is a mathematical manipulation of the sensor signal to give an output that will control a pump and manage a constant chlorine level in the water. All the features are adjustable and there are safety features built in such as overfeed protection. For a discussion of PID control please see our technical notes here.

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

The free chlorine sensors used by the analyzers are largely pH independent meaning that the measurements are bufferless and reagentless. They are amperometric sensors and show remarkable sensitivity and stability. For those needing to measure chlorine 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 transmitter 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 chlorine present, and the instrument gives a reading in ppm or mg/l.

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

The HaloSense range is bufferless and reagent free, meaning that it has a low total cost of ownership and with maintenance intervals of 1 year. HaloSense is fast becoming the instrument of choice for the engineer who wants the best instrument at the best price.

Focus Ons are a series of short articles distributed by email providing technical information regarding instrumentation, process measurement in potable, waste, process and pool waters. If you would like to join the mailing list, please contact us.

>> Small Water Treatment Plant Monitoring for Chlorine, pH and Turbidity

>> Using Open Flow Cells with Membraned Sensors

>> Seawater Chlorination

>> Zero Chlorine

>> Probe Fouling

>> Calibrating Sensors Using a DPD Kit

>> ppm Chlorine vs. ORP measurement