Online Chlorine in Sodium Hypochlorite Monitor - HypoSense

Measuring the chlorine content of bleach is difficult due to the aggressive nature of the fluid and is currently done by manual titration in a laboratory. The HypoSense allows the user to measure the chlorine content of industrial sodium hypochlorite (industrial bleach) online, continuously.

Why is it necessary to measure the chlorine content of bleach online and continuously? Surprisingly the chlorine content in bleach changes more than you might think. It degrades over time and is particularly affected by the level of impurities, the chlorine content when it was manufactured, and the temperature and UV level that it is kept at. Being able to measure the chlorine content online will provide for much better process control in those applications that use bleach as a reactant.

The HypoSense has been designed to three criteria:

  • The Best Sensor Available – the HypoSense is an optical measurement where the amount that a certain wavelength is absorbed is directly proportional to the amount of chlorine in a sample.
  • The Best Control Possible – for processes that require knowledge of the chlorine level in bleach such as in the manufacture of monochloramine (MCA), being able to use the actual chlorine content of the hypochlorite solution allows for tighter and better process control.
  • Reduced Costs – knowing how much chlorine is in your hypochlorite means that overdosing is a thing of the past. If you are a manufacturer of bleach then you can manufacture to the right concentration and not overshoot. All of these benefits will save you money in your process.

The HypoSense offers a number of key benefits.

  • Optical measurement meaning low maintenance and no reagents
  • Integrated temperature compensation for stable results
  • Simple pipe mounting for easy and inexpensive installation
  • Fully integrated with the CRIUS®4.0 controller
  • Robust and suitable for harsh environments

The HypoSense is a high quality controller giving you the best process control and the best value for money. For more technical information contact us today.


Sodium Hypochlorite (NAOCl or NaClO) is a chemical solution made up of chlorine and sodium hydroxide. It is an unstable chemical that can be stabilized using caustic soda (NaOH).

Sodium Hypochlorite is commonly known as bleach and is often used for disinfection purposes.

Industrial bleach is slightly different in that it is made up of sodium hypochlorite and sodium hydroxide, usually with up to 16% active chlorine.

This is dependent on the amount of sodium hydroxide that is present in the solution, although a pH of 12 to 14 is to be expected.

Chlorine levels in industrial bleach are prone to change. This is because industrial bleach can decay over time.

Nothing. Sensors are often affected by temperature, but the HypoSense has a built-in internal thermistor that allows for automatic temperature compensation meaning that you don’t have to worry about variations in temperature.

All of Pi’s chlorine sensors, including HypoSense, have very low drift rates so how often you calibrate your sensor, depends on the application. Our customers range from people who calibrate once a week to once a month, even to once every six months.

Usually the HypoSense is maintenance free as the bleach should keep the sensor clean. If the application is in very dirty bleach, the sensor may require additional cleaning.

Yes. The HypoSense uses light absorption to make a measurement, so bubbles blocking the flow of light will cause an erroneous reading. One way to solve this problem is to ensure the flow path is vertical rather than horizontal. This can be done when mounting the sensor. A vertical flow path will help to force the bubbles away.

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