½ hour measurements
The results are used for smog warning.
Ozone (O3) is measured by absorption of ultraviolet radiation. The air is drawn into a chamber and illuminated with ultraviolet light. O3 effectively absorbs light of a certain wavelength in the ultraviolet range. The concentration of O3 can therefore be determined from how much of the ultraviolet light is absorbed in the chamber.
Teknisk beskrivelse (engelsk)
Analyzing method: UV-absorption.
O3 monitors (API M400 and 400A):
- Principle: UV-absorption at 254 nm. The ratio between the absorption in the measurement cell with sample air and with absorption in the cell with O3 selectively removed permit calculation of the O3 concentration.
- Measuring range: 0-500 ppb, at 0.6-0.8 l/min.
- Lower detection limit: <1 ppb
- Precision ±5%
- Selectivity: Water vapour dilute the sample
- Routine checks: Automatic zero point check every day around midnight with zero- air from a generator, and "span" check by a built-in O3-generator.
- Calibration at the laboratory: 1) O3 from a generator traceable to NIST. Checked against a NIST reference photometer once a year.