Ozone Applications
Compare O3 Sensor Technologies
Ozone Sensor Principles Compared
There are different methods to measure ozone for safety and process control. Each method has distintive advantages and disadvantages.
-Heated Metal Oxide Ozone (HMOS) Sensor
UV Absorption Ozone Analyzer
UV absorption is considered the gold standard for ozone measurement due to its accuracy, stability, and long-term reliability. UV based Ozone analyzers operate based on the principle that ozone molecules absorb ultraviolet (UV) light at the specific wavelength of 254 nm.
Core Principle
Ozone strongly absorbs UV light at 254 nm. By shining UV light through a sample cell and measuring how much of that light is absorbed, the analyzer can calculate the exact ozone concentration using the Beer–Lambert Law.
UV Ozone Analyzers Explained in More Detail
Operating Mechanism of UV Ozone Analyzers
A UV ozone analyzer typically includes:
- UV Light Source
- Usually, a low-pressure mercury lamp producing stable UV light at 254 nm.
- Sample Cell (Optical Pathway)
- Sample gas is drawn through this chamber, and the UV light passes through it.
- Detector
- Measures the intensity of UV light after it passes through the sample.
- Reference Measurement
- A second optical path or filtered air stream provides a “zero ozone” reference.
- Signal Processing
- The analyzer computes ozone concentration based on the reduction in UV intensity caused by ozone absorption.
Electrochemical Ozone Sensors
Electrochemical sensors are one of the most common and practical methods for detecting low-level ozone in workplaces, ambient air, and safety applications. They are compact, low-power, and sensitive—making them ideal for portable detectors, fixed safety monitors, and personal exposure devices.
How Electrochemical Ozone Sensors Work
Electrochemical ozone sensors operate using a redox (oxidation–reduction) reaction that generates an electrical signal proportional to the amount of ozone present.
Electrochemical Ozone Sensors Explained in More Detail Click HERE
Core Principle
Ozone is a strong oxidizer. When it diffuses into the sensor and contacts the working electrode, it participates in a chemical reaction that produces electrons. These electrons create a measurable electrical current.
The current measured in a voltage change is directly proportional to the ozone concentration, typically displayed in ppm.
Operating Mechanism of Electrochemical Ozone Sensors
A typical electrochemical sensor contains:
- Gas-Permeable Membrane
- Allows ozone to diffuse in while blocking particles, humidity, and contaminants.
- Electrolyte Layer
- Provides the medium where the redox reaction occurs.
- Three-Electrode Cell
- Working electrode: Ozone is reduced/oxidized here.
- Counter electrode: Balances the reaction.
- Reference electrode: Maintains a stable baseline potential for accurate readings.
- Microcontroller / Signal Circuitry
- Converts the electrical current into ppm or ppb ozone readings.
Heated Metal Oxide (HMOS) Ozone Sensors
Heated Metal Oxide Sensor (HMOS) technology is a rugged, long-life method for ozone detection commonly used in industrial safety, equipment interlocks, and low-ozone environments. These sensors are known for their durability, fast response, and ability to operate in harsh environmental conditions where other sensor types may struggle.
How HMOS Ozone Sensors Work
HMOS sensors detect ozone based on changes in the electrical resistance of a heated semiconductor metal oxide surface when it interacts with ozone and other oxidizing gases.
HMOS Ozone Sensors Explained in More Detail Click HERE
Core Principle
A tiny ceramic bead or planar sensor element—typically coated with tin dioxide (SnO₂) or a similar metal oxide—is electrically heated to a controlled high temperature. When ozone molecules come into contact with this hot surface, they react with oxygen species on the sensor, causing a change in electrical resistance.
That resistance change is measured as a voltage change and converted into an ozone concentration reading in ppm.
Operating Mechanism of Heated Metal Oxide Ozone Sensors
- Integrated Micro-Heater
- Heats the metal oxide element to its operating temperature (typically 200–400°C).
- Metal Oxide Sensing Layer
- Exposed directly to the ambient air or sampled gas stream.
- Ozone Interaction
- Ozone, being a strong oxidizer, reacts on the sensor surface and alters the charge carrier density.
- Resistance Change Measured
- The electronics detect the change in resistance and translate it into a concentration signal.
Sensor Comparison
Ozone Sensor types compared
| Category | UV Absorption Analyzer | Electrochemical Sensor | Heated Metal Oxide (HMOS) Sensor |
| Measurement Method | Measures absorption of UV light at 254 nm using Beer–Lambert Law | Measures electrical current from ozone redox reaction in electrolyte | Measures resistance change of heated SnO₂ surface exposed to ozone |
| Accuracy | Very high accuracy (up to 1%) | Moderate, 10% accuracy | Moderate, up to 5% for liminted ranges, 10% typical |
| Drift Over Time | Minimal drift, continuous zero reference | Drift due to electrolyte consumption | Minimal drift, no consumable electrolyte |
| Consumable Components | None (UV lamp only) | Electrolyte is consumed by ozone | None (no electrolyte, no moving parts) |
| Sensor Life | UV-Lamp life of ~3-5 years | 6-months to 3-years | 2-5 years |
| Measurement Range | ppb to 25% wt / 500 g/m³, broadest measurement range | ppm range | ppb detection with upper range suited for ambient safety |
| High Level Ozone Tolerance | Excellent — no sensor damage | High ozone shortens sensor life | Good, no sensor life changes, limited accuracy of high ozone levels |
| Cross Sensitivity | Minimal — unaffected by oxidizing gases | Cross-sensitive to oxidant gases (NO₂, Cl₂, etc.) | High cross sensitivity to VOCs along with oxidant gasses |
| Humidity & Temperature Effects | Temperature and Humidity compensated | Sensor performance most affected by humidity & temperature | Wide operating temperature range due to internal heater, less affected by humidity than Electrochemical sensors |
| Power Requirements | Line-powered instrument | Ultra-low power, battery friendly | Low power, can be battery operated |
| Response Time | 10+ Seconds | Very fast (< 10 seconds) | Very fast (< 10 seconds) |
| Calibration Requirements | On-site calibration possible | Sensor can be replaced or shipped easily for calibration. Frequent ozone exposure will require more frequent calibration | Sensor can be replaced or shipped easily for calibration. |
| Portability | Fixed or benchtop use | Excellent for portable & wearable devices | Excellent for fixed long-term ozone detection, can also be battery powered and portable. |
| Regulatory Acceptance | EPA accepted for ambient ozone | Safety use only | Safety use only |
Ozone Monitor Information:
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We offer additional gas detection products in partnership with our subsidiary, Gas Sensing. For gasses other than ozone view the Gas Sensing website.
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