Optical particle size analyzer GFAS-DPOL

laser light scatteringfor environmental analysiswith data logger

Overview
The GFAS-DPOL combines a high-sensitivity forward and back scatter particle sizing measurement with polarization detection and an integrated ultrasonic anemometer for wind-speed and wind-direction. It is used to study fog formation, development and decay and to derive particle number concentration, liquid water content (LWC), extinction coefficient and visibility in warm and mixed-phase fog.

Features and benefits

• Detailed data on fog composition — Measures properties of complex fog/smog particles to support composition analysis and forecasting.
• Scatter optics plus polarization — Shape-factor and polarization measurements differentiate liquid droplets from ice crystals, dust or ash; refractive-index analysis indicates dissolved or insoluble material in droplets.
• Complete field solution — Integrated sample aspiration pump, control and data-logging computer, ultrasonic anemometer for wind speed and direction, self-orientation to wind, and power filtering/transient suppression.
• Lifecycle Care Program — Available maintenance and support program to preserve instrument integrity and performance.

Technology

• Ground-based single-particle optical spectrometer derived from airborne Cloud and Aerosol Spectrometers with Polarization.
• Forward-scattering optical geometry accepts and sizes particles passing through a uniform-power region of the laser beam.
• Forward-scattered light is split (50/50) and measured by photodetectors to determine particle size and depth-of-field response.
• Shape-factor and polarization detection enable particle-type discrimination (liquid droplets vs ice crystals, dust, ash).
• Complex refractive-index analysis supports inference of dissolved or insoluble material in droplets.

PADS – Particle Analysis and Display System

• User-friendly virtual instrument panel to control GFAS-DPOL and display real-time data and logs.
• Sample and record data.
• View particle volume and number concentrations, Median Volume Diameter (MVD) and Effective Diameter (ED).
• View liquid water content (LWC) as measured by the GFAS-DPOL.
• Monitor laser health and instrument temperatures.
• Reprocess recorded data with updated parameters for further analysis.

Main applications

• Visibility and fog studies; research into fog formation, development and decay; aerosol and cloud physics investigations.

Technical information
Measured Parameters:
Forward & back scatter measurements; Polarization detection measurements

Auxiliary Parameters:
Wind speed; Temperature; Pressure

Derived Parameters:
Particle diameter; Particle number concentration; Polarization ratio; Liquid water content; Effective diameter; Median volume diameter

Particle Size Range:
0.5 - 50 µm diameter

Number of Size Bins:
30

Typical Sample Area:
0.24 mm²

Sample Flow Volume:
1 m3/min

Sampling Frequency:
Standard data rate selectable, 0.04 s to 20 s (PBP); data rate limited only by particle coincidence

Refractive Index (default):
Non-absorbing, 1.33 (industry standard for water)

Light Collection Angles:
Forward: ~3.5° – 12°; Back: ~183.5° – 192°

Data System Interface:
Ethernet

Environmental Operating Conditions:
Temperature: -40 to 45 °C (except in heavy icing conditions); Relative Humidity: 0–100% non-condensing; Altitude: 0–4,000 meters

Probe Dimensions:
63 cm H x 39 cm W x 75 cm L

Power Requirements:
Universal power supply: 85–265 VAC / 50/60 Hz / 600 W

Characteristics / Technical specifications

• Model: GFAS-DPOL
• Brand: ENVEA
• Function: Ground-based fog & aerosol spectrometer with polarization detection
• Measured parameters: forward & back scatter; polarization detection
• Auxiliary parameters: wind speed; temperature; pressure
• Derived parameters: particle diameter; number concentration; polarization ratio; liquid water content; effective diameter; median volume diameter
• Particle size range: 0.5–50 µm
• Number of size bins: 30
• Typical sample area: 0.24 mm²
• Sample flow volume: 1 m3/min
• Sampling frequency: selectable, 0.04 s to 20 s (PBP); data rate unlimited until particle coincidence
• Refractive index (default): non-absorbing, 1.33
• Light collection angles: Forward ~3.5°–12°; Back ~183.5°–192°
• Interface: Ethernet
• Operating temperature: -40 to 45 °C (except heavy icing)
• Relative humidity: 0–100% non-condensing
• Altitude range: 0–4,000 m
• Probe dimensions: 63 × 39 × 75 cm (H × W × L)
• Power: 85–265 VAC, 50/60 Hz, 600 W