Figure 1 ICAD-NOx-200DL series featuring 19" rack housing and OLED display.
The ICAD (Iterative CAvity enhanced DOAS) NO2/NOx/NO measurement system uses direct optical absorption spectroscopy in the spectral range between 430 to 465 nm. In contrast to the ICAD 200 series, the “L” series features an enhanced sensitivity by using a longer absorption cell and increased reflectivity mirrors. By measuring the absorption spectrum and applying the ICAD algorithm, the unique and characteristic absorption structure of NO2 is directly identified and separated from other overlapping absorptions like water vapour (H2O) or Glyoxal (C2H2O2). This gives the advantage of direct NO2 measurements (in comparison to CLD) without interferences to other substances or the need of drying mechanism which introduce new interferences (e.g., 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 insensitive to temperature variations, vibrations and light source degradation like other optical instruments. An internal converter for NO to NO2 (optional) with a NOx free O3 source allows measuring also NOx/NO with the same system (patented). 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
SPECIFICATIONS
*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 regularly automated reference measurements.
*4 Literature absorption data for NOx is used for gas quantification.
*5 No significant spectroscopic cross sensitivity with respect to: Carbon oxides, Methane, H2CO, Hydrogen, Sulphide, Sulphur Dioxide, Chlorine, Chlorine Dioxide, Hydrogen Cyanide, Hydrogen Chloride, Phosphine, Hydrogen, Ammonia, Acetylene, Nitromethane, Ethylene, Ethanol, Methyl Mercaptan, Ethyl Mercaptan
APPLICATIONS
• High precision NO2 / NOx measurements (science, research, background air pollution monitoring)
• Urban air quality monitoring (outdoor, streets, tunnels, street canyons, mobile measurements)
• Indoor air quality and workplace monitoring
• Quick & precise NO2 / NOx pollution study, personal exposure studies e.g., for workspace, pedestrians etc.
• Emission monitoring (e.g., stacks)
• Real Driving Emission Measurement of vehicles (RDE): requires extra CO2 option to derive NOx / NO2 per km or kWh
THEORY OF OPERATION
Figure 2: Flow scheme and Measurement Principle of the ICAD NO2 / NOx / NO measurement system (incl. additional NO to NO2 converter for NOx measurement and optional CO2 sensor, e.g., for emission measurements).
Figure 3: Time scaled modified Allan deviation for NO2 and NOx measurements. Note: Detection limits are defined as twice the modified Allen deviation values.
ADVANTAGES
