Ozone monitors use the principle of UV light absorption to measure ozone concentrations in the air.
The Core Process of Ozone Monitoring
Here's a breakdown of how ozone monitors operate:
- Air Sampling: The monitor draws in two air samples, which consist of sample air and background air.
- Alternating Flow: The two samples are alternately pumped through measurement cells, labeled as cell A and cell B.
- UV Light Exposure: Inside the analyzer, both the sample air and the background air are exposed to UV light of a specific wavelength. Ozone molecules absorb light at this wavelength (specifically, around 254 nm). The amount of light absorbed is directly proportional to the ozone concentration in the air sample.
- Light Intensity Measurement: Each cell has a light sensor that measures the intensity of the UV light after it passes through the air. The difference in light intensity between the sample air and the background air is what allows the ozone concentration to be determined.
A Deeper Look at the Process
| Step | Description |
|---|---|
| 1. Air Intake | The monitor draws in ambient air. This air is then split into two streams: sample and background. |
| 2. Cell Switching | Sample and background air are alternately sent through the two measuring cells. |
| 3. UV Light Exposure | Both cells are exposed to a UV light source. Ozone molecules absorb UV light at a specific wavelength. |
| 4. Light Measurement | Sensors in each cell measure the intensity of the UV light after passing through the air sample. |
| 5. Data Analysis | The difference in light absorption between the two air samples indicates the amount of ozone present in the sample air. |
Why Two Cells?
Using two cells – one for the sample air and one for the background – allows the monitor to account for variations in the intensity of the light source, or any other factors that may affect light transmission through the cells. This results in a more accurate measurement.
Key Advantages
- Direct Measurement: This method directly measures the amount of ozone present, leading to accurate readings.
- Real-Time Data: Ozone monitors provide continuous, real-time data allowing for tracking of ozone levels over time.
- Non-Destructive: The process doesn't destroy or alter the air sample.
