Measures atmospheric visibility (meteorological optical range) by determining the amount of light scattered by particles (smoke, dust, haze, fog, rain, & snow) passing through the optical sample volume
A 42-degree forward scatter angle is used to ensure performance over a wide range of particle sizes
MOR is calculated by converting the received signal strength (extinction coefficient, σ) using Koschmieder's formula, MOR (Km) = 3/σ
Performance in all weather conditions is achieved with an integrated sensor design that keeps all sensor cabling internal to the sensor for complete protection against the weather
Made from anodized aluminum and rugged, UVresistant fiberglass enclosures rated to IP66
Based on the proven field experience of the NWS and FAA, the sensor uses a "look down" geometry to reduce window contamination and clogging from blowing snow
The optical windows have continuous duty anti-dew heaters and optional thermostatically controlled external hood heaters are available for protection in extreme environments.
All power and signal lines to the Visibility Sensor are protected with surge and EMI filtering to guarantee uninterrupted service for the life of the sensor
Installation and maintenance are simple. A mounting flange located on the bottom of the Main Enclosure Box mates with a user supplied 1-1/2 inch IPS mounting pipe
Power and signal cables are installed through waterproof cable glands on the bottom of the Main Enclosure Box to terminal boards for simple but reliable connections
Calibration in the field is simple. Attach a factory supplied calibration fixture and follow a short procedure (<30 min.) Semiannual calibration is recommended
This equipment is in compliance with the essential requirements and other provisions of Low Voltage Directives 73/23/EEC 89/336/EEC as amended by Directive 93/68/EEC
