Particle Sensor (Nephelometer)
|Sensor Code||AQM PMT/ PM10/ PM2.5|
|Sensor Type||Laser Nephelometer|
|Accuracy||<±(2 μg/m3 + 5% of reading)|
|Flow Rate||2L per minute|
|Lower Detectable Limit (2σ)||<1 μg/m3|
The particle sensor can be integrated into the AQM 65 along with gas analyzer modules to give continuous and simultaneous measurement of dust/particulate and gas.
The sensor combines a laser nephelometer with a high precision sharp cut cyclone to give accurate real time measurement of ambient particulate matter. By changing the sharp cut cyclone the particle sensor can be used to measure PM2.5, PM1 or TSP. For simultaneous measurement see the Particle Profiler.
A nephelometer is an optical sensor that uses light scattering from particulate matter to provide a continuous real-time measurement of airborne particle mass. The light source is a visible laser diode and scattered light is measured in the near forward angle using focusing optics and a photo diode. The nephelometer has an on-board temperature sensor which corrects for thermal drift, sheath air filter to keep the optics clean, automatic baseline drift correction and a fibre optic span system to provide a check of the optical components.
The sharp cut cyclone is a precision engineered component fitted to the AQM 65 inlet that physically selects particles of a target size e.g. PM10 targets particle <10 microns. This ensures precise measurement of only the size fraction of interest. The inlet is fitted with a heater that is used to remove moisture from the incoming sample. Moisture can reduce the accuracy of optical measurement, so for best results the inlet heater is activated in the event of high humidity.
Compared to reference instruments such as a beta attenuation monitor (BAM) this particle sensor based on nephelomtery is compact, lightweight and costs 3-5 x less to own and operate. In addition data is measured, logged and reported at one minute intervals.
Typical applications include:
- urban and national ambient air quality monitoring
- roadside and near roadside monitoring
- industrial perimeter monitoring
- mine and quarry boundary monitoring
- checking pollution ‘hotspots’
- air quality research