Bristol Industrial & Research Associates Ltd (BIRAL)

- Model VPF-510 - Visibility Sensor

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The VPF-510 Visibility sensor offers reliable visibility measurement in a robust and highly corrosion resistant package. The serial digital output supplemented by analogue outputs and switching relays makes this sensor particularly suited to offshore and marine applications.

The sensor can be configured to report either Meteorological Optical Range (MOR) or extinction coefficient (EXCO) in the serial data interface and on the voltage or current outputs. To further increase flexibility the sensor measurement range is configurable for the analogue outputs. When the sensor is required to drive a local warning beacon, sign or fog horn the relays can be used.

As standard the sensor is fitted with an extensive self-test monitoring capability which includes window contamination monitoring and output compensation. The VPF-510 can be AC mains or low voltage DC powered and hood heaters are available for use in areas prone to snow.

The sensor is fitted with 6m cables and is constructed from hard coat anodised dip brazed aluminium for superb corrosion resistance.

  • MOR or EXCO output
  • Highly corrosion resistant hard coat anodised finish
  • Window contamination monitoring and compensation
  • Serial digital and analogue outputs
  • Visibility threshold switching relays
  • 6m flying lead connections
  • VPF-500 replacement

Like all VPF series sensors the VPF-510 enclosure is constructed from dip-brazed aluminium with a hard coat anodised finish. This combination results in a sensor that offers superb abrasion and corrosion resistance. It is not unusual for VPF series sensor to be still operating after 20 years’ service in marine environments.

The 45° forward scatter angle and 850nm infrared light source used by the VPF-510 provide the best possible visibility measurement accuracy in all weather conditions. Visibility is output as Meteorological Optical Range (MOR) or extinction coefficient (EXCO) according to the user’s requirement.

In common with all Biral visibility and present weather sensors the VPF-510 uses 2kHz modulation of the light source combined with narrow pass band optical filters and synchronous detection at the receiver to ensure the measurement is not affected by bright or flashing lights. This design also ensures the sensor accurately reports visibility during precipitation. The horizontal hood design eliminates the problems caused by surface reflections that are a source of error in sensors employing look down hood geometries.

The optical windows of the sensor are fitted with low power heaters to prevent the formation of condensation. Window contamination monitoring and compensation allows the visibility output to maintain its accuracy even as dirt builds up on the optical surfaces. The sensor reports the window contamination in the output message using two stages of warning flags allowing cleaning to take place in a convenient manner.

Communication with the sensor is over a RS232 serial data link; RS422 or RS485 communications are optionally available. ASCII encoded data is used and the sensor can operate in either a polled or broadcast modes. The data message can include a time stamp from the internal real time clock in addition to the standard visibility and self-test information. The sensor is supplied with two user configurable threshold relays and one fault relay. One threshold relay can be configured to report the presence of precipitation. A voltage output is provided as standard which can be complimented with an optional current output.

The VPF-510 is available in both low voltage DC and mains AC power configurations. Optional hood heaters are available for use in environments where blowing snow may block the optical windows. The sensor is fitted with 6m fixed cables for all power and signal connections; other cable lengths are available on request.

The VPF-510 is a single lightweight unit that can be easily transported and installed by one person. It is designed for use in all weather conditions and has a wide operating temperature.

  • Measurement:
  • Visibility, MOR or EXCO
  • Output:
    • RS232, Optional RS422/RS485
    • 0 - 10 V
    • 4-20mA (optional)
    • 2 Threshold and 1 Fault Relay
  • Measurement Principle: Forward scatter 45°
  • Measurement Error: 2% at 2,000m
  • Sensor Power: 12 V DC, 24V DC, 120 V AC or 240 V AC (6W Approx)
  • Hood Heating Power: 30W
  • Window heating and contamination monitoring: Fitted
  • Operating Temperature: -50°C to 60°C
  • Operating Humidity: 0 – 100% RH
  • Protection rating: IP66
  • Weight:
  • Sensor Head: 4.9 kg DC: 6.1kg AC
  • Cables: Approx. 3 kg

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