EcoChem Analytics

Model PAS 2000 - Photoelectric Aerosol Sensor (PAS)

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Since 1991, EcoChem has pioneered the use of the Photoelectric Aerosol Sensor (PAS) for real-time measurement of Carbon aerosols. Previous versions of the PAS monitor (PAS 1000i, 1000e and 1002i ) are widely used by regulatory, research and industrial organizations. Incorporating customer feedback and state-of-the-art advances in measurement techniques, the PAS 2000 features the following technological advances: Use of an UV Excimer lamp. This lamp has a higher efficiency than any traditional UV lamp. The Excimer lamp can be rapidly switched on and off without a time delay. The offset produced by pre-charged particles can be eliminated by operating the lamp in a chopped mode.The Excimer lamp produces monochromatic radiation with a half bandwidth of 2%. Higher sensitivity instrument with a larger measurement range. Total microprocessor control with internal data acquisition and storage

Applications

  • Outdoor ambient air quality and monitoring in special settings like parking structures, traffic intersections and motorway tunnels
  • Indoor air quality in homes, offices and monitoring indoor sources like kerosene heaters, wood stoves and environmental tobacco smoke
  • Workplace monitoring in industrial environments where PAH are produced
  • Monitoring carbon aerosols during special situations like Forest Fires, Scrap Vehicle Tire Fires and Agricultural Burns
  • Emissions from Combustors, Refinery Heaters, Industrial Boilers and Furnaces
  • Emissions from Municipal, Hazardous and Medical Waste Incinerators
  • Exhausts from Diesel and Gasoline Engines
  • Emissions from Industrial Processes like Coke Ovens, Petroleum Catalytic Cracking, Iron and Steel Foundries, Aluminum and Carbon Black Manufacture

Features

  • Uses patented Excimer Lamp technology to detect particle-bound PAH continuously in real-time
  • Responds to ultrafine respirable particles which act as carriers of PAH into the body
  • Signal has be correlated to particle-bound PAH, Elemental Carbon (EC) and other soot measurement techniques. These carbon aerosols pose the maximum health risk
  • Sensitive in the nanogm/m3 to microgm/m3 range
  • Simple, reliable, field-rugged and proven technology
  • Automated operation requiring minimum human intervention. Built-in data acquisition for 2500 data points
  • Proven source monitoring with special dilution sample system

Measuring Principle
The PAS 2000 works on the following principles:

  • Using an Excimer lamp the aerosol flow is exposed to UV radiation. The Excimer lamp offers a high intensity, narrowband source of UV radiation. The wavelength of the light is chosen such that only the carbon aerosols are ionized, while gas molecules and non-carbon aerosols remain neutral.
  • The carbon aerosol particles emit electrons, which are subsequently removed when an electric field is applied.
  • The remaining positively charged particles are collected on a filter inside an electrometer, where the charge is measured. The resulting electric current establishes a signal, which is proportional to the concentration of Elemental Carbon and/ or PAH.


Also by operating the Excimer lamp in a chopped mode, the PAS 2000 can eliminate the background signal, which is associated with freshly generated aerosols. The chopped mode also enables a dynamic zero to be generated automatically by the instrument.

Calibration
Source-specific calibration curves are available or can be generated where the monitor output is compared to an analytically determined EC and PAH concentration. A site-specific calibration curve can provide greater accuracy for the particle size, charge and compound-specific to the source. In addition to the site-specific curves, an approximate universal calibration curve can be used for screening and real-time trending applications.

Chassis and Mounting
Housing Options The ambient air PAS 2000 can have the following housing options:

  • Standard desktop unit
  • Rack-mount unit

Technical Specification

  • Display: LCD Panel with 128 by 64 pixel resolution
  • Power: 115 volts AC / 60 Hz & 220 volts AC / 50 Hz, Max. power consumption 35VA
  • Range: 0 to 100 picoamp (user selectable)
  • Sensitivity: Calibration is site-specific (ng/m3 to microgm/m3)
  • Lower Threshold
  • Response time: < 10 seconds (adjustable)
  • Analog Output: (0 to 10 volt) and ( 0 to 20 mA or 4 to 20mA )
  • Digital Output: RS - 232
  • Sample gas: Built-in pump with flowrate controlled at 2 L/min
  • Operating temp: 40 to 104 ºF (5 to 40ºC)
  • Dimensions: Standard Desktop Unit ( Height x Width x Depth ) 4.5in x 9.3in x 12.5in ( 133mm x 236mm x 317mm )
  • Weight: 20 lb. ( 9 kg )
  • Data Storage: 2500 Data Points (each data point consisting of : Date, Time, Value )
  • Software: User-friendly PC-compatible graphical software collects data from PAS 2000. The software displays real-time strip charts and calculates averages. Data is stored in a variety or formats. Flat ASCII file output can also be generated for further analysis in standard spreadsheet programs (e.g. Microsoft Excel).
  • Data Acquisition Software: User-friendly PC-Compatible graphical software collects data from PAS 2000. The software displays real-time strip charts and calculates averages. Data is stored in a variety of formats. Flat ASCII file output can also be generated for further analysis in standard spreadsheet programs (e.g. Microsoft Excel).

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