Trace gas handling and monitors
Contact: Dr. Harald Saathoff
AIDA trace gas handling system:
For the controlled supply of trace gases to the AIDA simulation chamber a stainless steel vaccum system is used. It allows for quantitative addition of trace gases from gas cylinders, glas bulbs, or cooling traps. Quantification is realised by using certified gas cylinders, by measuring the vapour pressure (4 MKS Baratron ranges: 10 hPa, 100 hPa, 1000 hPa, 30000 hPa) of trace gases in the glas bulbs or cylinders, and by controlling the volume added to the AIDA chamber using calibrated mass flow controllers.
AIDA trace gas monitors:
The trace gas monitors are connected to the AIDA chamber via Teflon (FEP) tubes ranging ~40 cm into the chamber. Sampling is done either continously or intermittent using automated valves. Signal output of the gas monitors is directly connected to the AIDA data aquisition & visualisation system and stored in the AIDA database.
Ozone concentrations are measured by UV absorption:
|
Ozone Instuments |
Measurement range | Detection limit | Sample flow | Calibration |
|---|---|---|---|---|
| Environment O341M | 0 - 10 ppm | 1 ppb | 0.5 l/min |
Ansyco GmbH |
| Monitor Labs 9811 | 0 - 20 ppm | 1 ppb | 0.5 l/min | comparison with reference instrument |
NO/NO2 concentrations are measured by fluorescence and photolytic conversion using a combination of two instruments and by Cavity Attenuated Phase Shift (CAPS):
| NO/NO2 Instruments | Measurement ranges | Detection limit | Sample flow | Calibration |
|---|---|---|---|---|
| ECO Physics CLD 77 AM | 0 - 10, 100, 1000, 10000 ppb | 20 ppt | 50 - 350 ml/min | certified gas mixtures |
| ECO Physics PLC 760 MH | selective conversion of NO2 into NO with UV (320-420nm) | - | " | certified gas mixtures |
| Environment AF32M (NO2) | 0-1 ppm (CAPS) | 0.1 ppb | 1 l/min | certified gas mixtures |
NH3 concentrations are measured by cavity ring down spectroscopy:
| NH3 Instrument | Measurement ranges | Detection limit | Sample flow | Calibration |
|---|---|---|---|---|
| Picarro G2103 | 0-500 ppb (0-10ppm) | 0.1 ppb (300 s) | >1500 ml/min | certified gas mixtures (via CO2) |
SO2 concentrations are measured by fluorescence:
| SO2 Instrument | Measurement ranges | Detection limit | Sample flow | Calibration |
|---|---|---|---|---|
| Environment AF22M | 0-0.1/ 0.2 / 0.5 /1 / 2 / 5 / 10 ppm | 1 ppb | 300 ml/min | certified gas mixtures |