HSS VPF-710 fog / visibility sensorHSS sensors with unrivalled accuracy and long-term reliability |
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Links to previous pages Fog / Visibility
Section
_______________ Tel UK: 01275 847787 Fax UK: 01275 847303
by Biral to rigorous IS0 9001:2000 quality standards. _______________ |
As with all the HSS sensors the HSS VPF-710 sensor
is configured for accurate measurement of visibility in the densest of fogs to very clear
air conditions and is the refinement of 2 decades of experience and technology resulting
in a compact, robust instrument with excellent performance. Originally designed for the US military, the HSS VPF-710 is suitable for use in any system where a digital output is required and sophisticated levels of remote monitoring are desired, for example on road or national weather networks feeding data back to a central collection point. It is a very compact, robust instrument with all electronics contained in the sensor head. It has excellent time proven performance and is suitable for use in extreme conditions.
The VPF-710 sensor uses forward scatter meter technology to measure visibility in all weather conditions. The sensor measures the amount of light scattered by small suspended particulates (i.e. fog, haze and smoke aerosols) or larger particles (i.e. rain, snow, ice pellets, drizzle and mist) passing through the sample volume. The sensor calculates the atmosphere EXtinction COefficient (EXCO) from which the Meteorological Optical Range (MOR) is calculated. Using an infra-red light source and intelligent sensing technology the measurements are unaffected by other light-sources. 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. The HSS VPF-710 is a single lightweight unit and can easily be installed by one person. The sensor is constructed of dip brazed high grade aluminium. All components that are exposed to weather are hard-coat anodised for protection against corrosion. Maintenance and calibration 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 below. Operation in temperature extremes The sensor operates in temperatures ranging from - 58º F to + 140º F. For operation below - 27º F the heated version is recommended (please refer to the heated option below). The VPF-710 System The sensor is constructed of high quality aluminium which is hard anodised to give a superior finish that lasts for years and does not require painting. As standard the sensor has:
Self-test and monitoring system The sensor condition and performance can be monitored remotely using the self-test diagnostic software which comes as standard to monitor:
Even greater self-test and monitoring is available with the optional advanced self-test and monitoring system (see below under variations) In addition the following variations are available:
Alternative Variants / Options Heated version - the sensor is fitted with window de-misters allowing operation of the sensor in temperatures down to 27º F. However, where the temperature drops below 27º F for more than a couple of hours a day the heated version is recommended. This version will provide error free operation in conditions down to - 58º F.The operational range of the sensor is from - 58º F to + 140º F. The heated version is available for all mains powered units (any voltage between 100-250 VAC) and 24 VDC battery powered units. However, please note that there is a restriction on heaters for 12 VDC units. A low power heater can be provided but it will operate at half of the standard rating (standard heater output = 15 W per hood and reduced heater output = 7 W per hood). The reduced heating units can be controlled by three methods: 1. ON all of the time...power hungry but effective. 2. OFF all of the time...conserve power but may ice up if snow accumulates. 3. Switched on and off situation depending on the temperature settings monitored internally by the sensor (best use of power and error free measurements).
RS-422 communications - where there is 39 ft or more between the sensor and control computer RS-422 configuration is required. Ambient light sensor - allows ambient light conditions to be measured according to ICAO (4 level and with specific angle of view). Designed for use with RVR (Runway Visual Range) systems on airfields and for use with Allard’s Law if night time visibility conditions are to be determined according to this instead of using the standard Meteorological Optical Range values (MOR). Weather station module - provides 3 analogue inputs (0-10 V) allowing the VPF-710 to be used as a weather station. Output is a single time correlated data string. Advanced self-test and monitoring system - provides increased levels of diagnostic testing which in addition to the functions of the standard self-test and monitoring will also allow you to monitor:
For accessories see below Examples of data output Please see the linked data example (pdf)
The benefits of an HSS sensor As with all the sensors in the HSS visibility sensor range there are a number of benefits which have been proven over many years of operation: Long-Term Reliability The Biral HSS sensors are designed to withstand years of abuse problem free and are the best choice for long life expectancy. For two decades customers such as the Dutch Motorway Authorities have been using HSS sensors and they are still enjoying the reliability and durability of the sensors (most have run the entire time without a single problem!). The US Military also continues to uses Biral HSS sensors in land and maritime roles. Extensive Trial History As Biral HSS sensors were the first sensors on the market, we have an extensive library of independent test results comparing the HSS brand against the competition. Not only do the reports show excellent performance but also Biral can show the consistency of the sensors’ performance since their conception in 1984. The sensors have been used by nearly every national weather service, several defence organisations, aviation authorities, offshore oil platforms, numerous lighthouse authorities and institutes carrying out meteorological research. Indeed, in the past, we have even sold to our competitors! References and test reports are available on request. Lightweight and Low-Powered Biral HSS sensors are some of the lightest around and can easily be installed by a single person. They are also designed for very low power consumption, allowing additional flexibility for a wider range of applications. HSS Sensors were developed two decades ago and were the first Forward Scatter Meters (FSM) to use an infra-red light-source, they have remained ahead of the competition ever since. There are three models available, all offering: Corrosion-Free Corrosion is not an issue with HSS sensors due to the fact that we only use hard-anodised aluminium combined with a salt-dip brazing process. The dip brazing ensures that the sensor enclosures are strong and leak-free while the military standard anodising provides unrivalled corrosion resistance. The extra expense of this process has proven worthwhile for strength, accuracy and long-term durability. Performance and quality are paramount and only the best results are accepted. Unbeatable Accuracy The combination of design, light-source type, wavelength and undisturbed sample volume gives Biral HSS sensors unbeatable accuracy. Design Using a unique patented design, the HSS range is considered to provide the best correlation of extinction coefficient (EXCO) to observed visibility. In reduced visibility conditions, whereas other sensors using different scattering angles report only precipitation, Biral HSS sensors continue to provide accurate visibility AND precipitation data. Light-Source The light-source is an infra-red diode which has been proven to provide higher accuracy, longer life and much more consistent readings than sensors using visible light-sources. The patented design of the HSS sensors means that no other sensor can match their performance. Wavelength Biral’s choice of light-source and wavelength (880 nm) is considered to be the best for accuracy where it counts most - around the 1 mile range. The choice of the wavelength is critical when deciding how the sensor performs in terms of accuracy and shifts in light spectra. The wavelength used is perfect for the shift in light from white (visibility below 1 mile) to blue (visibility from 1 mile to several miles). Almost all sensors using FSM technology can detect the white spectrum well, but HSS Sensors also detect the shift from white to blue spectrum and therefore maintain accuracy values to much higher visibility ranges. Undisturbed Sample Volume Accurate visibility and precipitation measurements require the sample volume to see only what is actually present. Other designs often suffer from precipitation splashing off the instrument enclosure, turbulence effects and unwanted reflections. The unique design of Biral HSS sensors ensures that the sample volume remains undisturbed regardless of wind direction and precipitation conditions. Optical Geometry Reflections from snow and surface water may cause measurement errors if they are allowed to enter the receiver, a common problem in some sensor designs. The sensor heads of all Biral HSS sensors are positioned in the horizontal plane to ensure that the measurements are not influenced by surface reflections. Biral HSS sensors also provide "no-dew window heaters" and optional hood heaters to ensure that the heads remain free from mist and obstruction even in the most challenging blowing snow conditions.
Specifications of VPF-710 visibility / fog sensor
*FSM = Forward Scatter Meter ***MTBF = Mean Time Before Failure
E&OE
Calibration reference kit - recommended for end-user confidence checks and recalibration. The kit contains a carrying case, zero plugs and a calibration plaque to a specific EXCO value. One kit can be used on any number of sensors of the same range. Stainless steel mounting kit - includes a U-bolt and fasteners to secure the sensor to any pole with a diameter between 1.5 - 2.5 inch. Transit case - scientific case lined with 3 inch foam to hold the sensor securely in place in extreme handling conditions. This unit is usually dispatched within 2-4 weeks ARO (After Receipt of Order) Warranty The VPF-710 Visibility Sensor comes with 2 years warranty as standard. After Sales Support Biral offers free advice and technical support for the lifetime of the instruments we sell. Once you have purchased the unit you can contact us for help on wwwmetsuppport@biral.com |
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| Links to previous pages Fog / Visibility
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| Links to previous pages Fog / Visibility
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| Links to previous pages Fog / Visibility
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| Links to previous pages Fog / Visibility
Section
Tel UK: 01275 847787 Fax UK: 01275 847303 Email: wwwmet@biral.com |
Not sure if this is the right sensor for you and would like help selecting a sensor? email us: wwwmet@biral.com
This range is in continuous development therefore specifications may change without prior notice. E&OE
Thank you for visiting www.biral.com/met/fog/vpf710.htm |
