CAPS PMex Monitor

The CAPS PMex monitor provides a measurement of the optical extinction (the sum of scattering and absorption) of an ambient sample of particles.  Currently, there is a choice of 5 different wavelengths – blue (450 nm), green (530 nm), red (630 nm), far red (660 nm ) and near infrared (780 nm, at additional cost)  – which match the spectral bands of most other particle optical properties measurement equipment.  These instruments have a 1 second time response and provide a level of detection (3σ) less than 2 Mm-1 with 1 second integration time.  These monitors are entirely self-contained, requiring no consumables such as zero air and can be operated autonomously for over 12 months using on-board data storage if one second averaging is chosen.

Measured particle extinction at 630nm in Pasadena, CA during the CalNex campaign shown as 1 hour average values. Note the diurnal variation in extinction levels.

Measured particle extinction at 532 nm outside of Estes Park, CO shown as 1 minute averages. Note the low levels of ambient particle extinction. The spikes are particulate emissions from passing vehicles

  • Measurement of particle optical extinction using patented Cavity Attenuated Phase Shift technology with a choice of 5 different wavelengths ranging from 450-780 nm.
  • Measurement of ambient optical extinctions at the 1 Mm-1 level.
  • Climate Change Research
    Optical Properties Closure.
  • Roadside Monitoring.
  • Combustion Plume Analysis.
  • Aircraft Engine Exhaust Monitoring.
  • Choice of 1 of 5 Wavelengths:

    Near Infrared  (780 nm)

    Far Red (660 nm)

    Red        (630 nm)

    Green     (525 nm)

    Blue      (450 nm)

  • No calibration required.
  • Autonomous Operation:
  • No Zero Air.
  • Automated Background Subtraction.
  • Linear Response (0 – 2000 Mm-1).
  • Maintenance-Free.

Sensitivity (S/N =3)2.5 Mm-1 (1 s), 0.25 Mm-1 (60 s)Response Time(10-90%)< 2 sSample Flow0.85 l min-1 (volumetric flow)Operating PressureAmbientMaterials Exposed to SampleCopper, Stainless Steel and AluminumSize/WeightRack mount, 19” x 24”, 25 lbs
[61 cm x 43 cm x 23 cm, 12 kg]Electric Power50 W; 100-250 VAC (50-60 Hz)
Data OutputRS-232 (Data acqusition and instrument control software provided)On-Board Data Storage (6 GB)Download through USB Port Front Panel Display

Aerosol light extinction measurements by Cavity Attenuated Phase Shift Spectroscopy (CAPS): laboratory validation and field deployment of a compact aerosol extinction monitor, P.Massoli, P. Kebabian, T. Onasch, F. Hills,A. Freedman, Aerosol Sci. Technol., 44, 428–435 (2010).

System and method for trace species detection using cavity attenuated phase shift spectroscopy with an incoherent light source, P.L. Kebabian and A. Freedman, U.S. Patent No. 7301639 (issued November 27, 2007)

Optical Extinction Monitor Using CW Cavity Enhanced Detection, P.L. Kebabian, W.A. Robinson and A. Freedman, Rev. Sci. Instrum., 78, 063102 (2007)

♦ For more information on our CAPS monitors contact Dr. Freedman: