HSS VF-750 Sensor Description

The VPF-710 digital visibility sensor is designed for accurate measurement of visibility and has been in operation for over 20 years. It is a compact, robust instrument with excellent time proven performance and is suitable for use in extreme conditions.

Measurement Principle

The VPF-710 sensor uses forward scatter meter technology to measure visibility in all weather conditions. The sensor calculates EXCO (the atmospheric EXtinction COefficient) by measuring the amount of light scattered by small suspended particulates (ie fog, haze and smoke aerosols) and larger particles (ie rain, snow, ice pellets, drizzle and mist) passing through the sample 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 communications available as an option. The data is output in various ASCII data strings, such as a small compressed data string, expanded data string and monitoring data string amongst others. The unit can be 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 by one person 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.

Operation in temperature extremes

The sensor operates in temperatures ranging from -500C to +600C. For operation below - 30C the heated version is recommended (please refer to the variants overleaf).