The ICAD (Iterative CAvity enhanced DOAS) HONO / NO2 measurement system uses direct optical absorption spectroscopy in the spectral range between ~ 360 to 390 nm. By measuring the absorption spectrum and applying the ICAD algorithm, the unique and characteristic absorption structures of HONO and NO2 are directly identified and separated from other overlapping absorptions like water vapour (H2O) or O4. This gives the advantage of direct HONO and NO2 measurements (in comparison to LOPAP and CLD) without interferences to other substances or the need of drying mechanism which introduce new interferences (e.g., LOPAP, CLD, CRD, CAPS). As the ICAD system relies not on absolute intensities, but rather characteristic differential absorption structures, it has no absolute zero-point drift and is almost completely insensitive to temperature variations, vibrations and light source degradation as found for other optical instruments. It is thus the perfect tool for accurate and precise long-term measurements, but also for mobile applications requiring a wide measurement range, high precision and fast response times. The operation is simple as no consumable gases are required. Data display is directly available with any WiFi or LAN device or over the RS232 interface. 

Patents: DE102015000423; EP3329251; US15/748,923; China ZL201680057099.6, EP3325928

SPECIFICATIONS

COMMENTS

*1 Custom specifications with different measurement range are possible. By reducing the measurement range better precision and LOD can be achieved.

*2 Response: Different measurement cell types are available, allowing different response times. Smaller measurement cells allow a much faster response time, but result typically in a lower precision.

*3 Upper limit. Drift is negligible due to twice daily automated reference measurements.

*4 Regular automatic determination of the absorption path by light source modulation.

*5 No significant spectroscopic cross sensitivity with respect to: Carbon oxides, Methane, Hydrogen, Sulfide, Sulfur Dioxide, Chlorine, Chlorine Dioxide, Hydrogen Cyanide, Hydrogene Chloride, Phosphine, Hydrogen, Ammonia, Acetylene, Nitromethane, Ethylene, Ethanol, Methyl Mercaptan, Ethyl Mercaptan, Formaldehyde, Ozone < 1ppm

APPLICATIONS

• High precision HONO / NO2 measurements (science, research, background air pollution monitoring)

• Urban air quality monitoring (outdoor, streets, tunnels, street canyons, mobile measurements)

• Indoor air quality and workplace monitoring

• Mobile, quick and precise HONO / NO2 pollution study, personal exposure studies e.g., for workspaces, pedestrians

• Emission monitoring (e.g., stacks)

THEORY OF OPERATION

Flow scheme and Measurement Principle of the ICAD HONO / NO2 measurement system.

Time scaled Allan Deviation for HONO and NO2 measurements.

ADVANTAGES