Ozone Sensor

Ozone Sensor Tip

OzoSense Residual Ozone Analyzer from PI for the measurement of ozone concentration in water, is designed to be simple to install and operate and offers unrivaled stability, accuracy and precision, while offering excellent value for money.

The OzoSense range of Ozone Analyzers, Ozone Controllers and Ozone Monitors utilize the very latest and best ozone sensors available in the world today. They are membrane devices which are insensitive to changing pH, use no reagents, are extremely stable, and have reduced maintenance and reduced whole life costs.

New! Now available with up to four ozone sensor inputs.

  • Stable and reliableexcellent process control
  • Suitable for all potable, process and salt waters
  • Up to 6 months between maintenance
  • Up to 3 months between calibration
  • Does not respond to residual chlorine
  • Resistant to detergents in the water

The OzoSense sensors and flow cells are available with different controllers giving you the same great performance with different communication, display, and control options. With the OzoSense range of residual ozone analyzers, you get everything that you need – and nothing that you don’t, saving money without compromising the quality of measurement.

The OzoSense Residual Ozone Monitor suffers no interference from other oxidants such as Chlorine. Coupled with its excellent zero and calibration stability it is extremely well suited to the monitoring of the Residual or Dissolved ozone concentration in water in clean or harsh environments.

The Residual O3 Monitor is bufferless and reagent free, meaning it has a low total cost of ownership and with maintenance intervals at 3 or even 6 months, the bufferless Ozone Monitor is fast becoming the instrument of choice for the engineer who wants the best ozone monitor at the best price.

Principle of Operation

The membraned amperometric ozone sensors are two electrode sensors which operates at an elevated applied potential which in turn eliminates zero drift. Its unique design means that no reagents or buffers are required at all.

In addition to the state of the art amperometric chlorine dioxide sensors the OzoSense range of ozone analyzers has all the functionality that you need, and more. Simply choose the CRONOS, CRIUS® or CRATOS controller to give you the highest quality ozone monitor, 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.

OzoSense at installation in Turkey

OzoSense at installation in Turkey

OzoSense Water Treatment Applications

  • Ozone Dosing Control
  • Remote Sites
  • Cooling Towers
  • Food Preparation
  • Hospitals
  • Secondary Ozonation

Anywhere you have a requirement to measure residual ozone is a suitable application for the OzoSense. The OzoSense ozone monitor range is particularly suited to working in sites where reliability and ease of use are most important. The sensor is resistant to the presence of tensides making it suitable for use in many washing applications.


As described in a separate brochure, the OzoSense can come equipped to automatically clean itself at user defined intervals with all the benefits of no operator intervention for 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.

Multi-Sensor Systems

The whole range of OzoSense Ozone Monitors and Controllers can be fitted with additional sensors such as more ozone sensors, chlorine, pH and many others. Please ask your local distributor for more details.

What range of sensors are available?
Pi offers ozone sensors from a range 0.05-0.2, 0.05-0.5, 0.05-2, 0.05-5, 0.05-10, 0-20 mg/l (ppm)

Can I measure ozone in seawater?
When you add ozone to seawater you get bromine. Pi offers a total bromine sensor for this application.

How often do I calibrate my sensor?
This depends on the application. The online residual ozone sensor has a very low drift so most people calibrate it either once a week or once a month.

How often do I change the ozone sensor electrolyte?
Every 3-6 months

Can I measure ozone in the presence of tensides (detergents)?
Yes, the OzoSense is resistant to the effects of tensides.

Can I operate the sensor at an overpressure so I can return the sample to the process?        
Yes and No. The sensor can operate at 1 bar overpressure but the pressure must be constant or the reading will vary. This is usually not enough to put the sample back into a process so most customers use an open flow cell to ensure a constant pressure.

Will changing pH affect the reading?

What is the shelf life of the membranes and electrolyte?
If stored in a cool dry place, two years.

What are the interferences?
There will be a small response to residual chlorine  (<2%) and also to chlorine dioxide (<7%).

What are the materials of construction?
PVC and stainless steel

What is the Temperature range of the sensor?
>3 °C – < 50 °C

Why is there no zero adjustment?
The sensor operates at a positive voltage all of the time so any drift on the zero is negligible compared to the positive operating voltage so no zero is necessary.

What will happen if the temperature varies?
Nothing! The sensor has a thermistor that measures the temperature and does an automatic compensation.

What should I use to calibrate the sensor?
Use a handheld meter. These are available from a variety of suppliers and nearly all of them utilise colourimetric DPD to determine the ozone concentration in the sample.

What do I have to think about when I am taking a sample to do a DPD test?
Firstly take the sample from right at the instrument. Secondly don’t take the sample when the concentration is varying quickly, and thirdly use a good quality handheld and follow the instructions carefully.

I have tried to calibrate and the analyzer says that the sample wasn’t stable?
During calibration the analyzer looks at the stability (rate of change) of the signal from the probe and if it varies by more than 10% over the countdown then the analyser prevents calibration to avoid the calibration routine introducing errors.

What is Ozone?
Ozone is an allotrope of Oxygen having the chemical formula O3. It is three Oxygens joined together. If decays to O2.

Why is Ozone used to disinfect water?
O3 is a powerful oxidant and can therefore be used to disinfect water. Specifically it can:

  • React with and remove manganese
  • Destroy some pathogens resistant to chlorine such as Giardia and Cryptosporidia.

Why Is Ozone favoured for some applications?
Ozone disinfects and leaves no taste or odour. In addition it completely breaks down urea so doesn’t form organochlorine or combined chlorine products.