HSS VPF-730 Sensor Description

The VPF-730 sensor is one of a kind, being the only forward scatter meter to measure visibility AND present weather (WMO 4680) including precipitation type and rate. It is a compact, robust instrument with excellent time proven performance and is suitable for use in extreme conditions. The sensor is designed for accurate measurement and has been in operation for over 20 years.

Present Weather
Present Weather includes: all forms of liquid, freezing and frozen
precipitation; e.g., rain, drizzle, snow, snow pellets, snow grains, ice pellets (formerly sleet) and hail, and those suspended particles that are classed as obstructions to vision; namely, mist, fog, haze, dust and smoke.

Measurement Principle

The sensor calculates EXCO (the atmospheric EXtinction COefficient) by measuring the amount of light scattered by the particles in the sampling volume. From this EXCO value the MOR (Meteorological Optical Range) and thus visibility is determined.

Data Output

The sensor is configured with RS-232C signal output as standard with RS-422 communication available as an option. The data is output in various ASCII data strings, such as a small compressed data string, expanded data string and remote maintenance data string amongst others. The unit canbe set in either automatic or polled mode and data sent to a printer or to a PC for tagging, processing and archiving.

Maintenance, calibration, self-test and monitoring

The sensor is fully calibrated at the time of manufacture. Routine
maintenance, including a check on calibrations, can be performed easily in a matter of a few minutes and a re-calibration (although this should never be required) takes only slightly longer. The sensor condition and performance can be monitored remotely using the self-test and monitoring system detailed overleaf.