Aerosol Instrument Calibration
Verifying the calibration of aerosol instruments in the field is generally more complicated than for gas analyzers. Calibration aerosols must be generated as required, whereas span gases for gas analyzers may be stored in bottles at known concentrations until needed.
When measuring aerosol, many instruments measure size/number spectra. This poses an additional complication- the instrument's sizing accuracy must be checked, in addition to the number measurement accuracy.
Number Calibration Check
Verifying the number measurement accuracy of an aerosol instrument is particularly difficult- traditional techniques use electrometers to verify the calibration aerosol concentration, and these require an electrical neutralizer to provide the necessary charge distribution. These devices are usually radioisotope based, which places severe limits on the ease of transporting / using them.
Size Calibration Check
The commercial availability of NIST traceable aerosol size standards offers the possibility of a simple sizing accuracy check, which does not require radioactive sources or compressed air.
(The particle size is large enough that residual charge is not significant in electrical mobility instruments which employ corona chargers such as the Cambustion DMS500)
The process is as follows:
- Concentrated Poly Styrene Latex size standards in suspension with water and surfactant (as purchased).
- Dilute with distilled water to reduce concentration.
- Aerosolize using portable nebulizer.
- Remove water from surface of PSL particles via diffusion drier.
- Feed dried PSL particles into instrument under test and measure response.
Please contact Cambustion for further information.