Air Temperature with Solar Radiation Shield

Measures temperature of convected air currents, air without solar radiation ( ie shaded ) by using a white gill screen which eliminates the warming effect of energy from direct sunlight. Sense element and 6 gill screens weigh 300g. The sensor is of a precision semiconductor type giving an output 10mV per °C. Accuracies of 0.25°C are typical. Running on +12v DC, operating between -40 to +110°C. .Response time of sensor housed in screen is approximately 10 seconds given that the wind movement is > 10 mph. Sensor requires no maintenance.

Temperature Interpretation
Current temperature is shown as a whole figure [integer] (10°C) in Celcius with a representation in Fahrenheit. Maxima and Minima values are shown with one decimal place (10.3°C) and time at which these occurred. Air now temperature is retrieved every 30 seconds. Max and mins are reset once per 24 hours usually at 23:45 but can be user defined. Temperature and Windchill online HTML graphs are generated from historical records which in addition to high resolution graph facilities offer a quick recent look at these trends.

Wind Chill is calculated using Air and Windspeed. The value relies on speeds being greater than 3 mph and temperature less than 33°C.

Dewpoint can also be calculated, this is the temperature at which air becomes saturated with water at a constant pressure, the water no longer being a vapour, for example early morning dew. Requires information from a Humidity Sensor.

Windspeed Anemometer

Measures movement of air at the preferred height of 10 metres and converted into either Miles per hour, Metres per second, Kilometres per hour or UK Knots by the equipment. Sense method is achieved by a Hall effect semiconductor affected by rotating magnet. Uses +12v DC. Accuracy upto 70 mph is ±1 mph. Cups and body are one piece injection moulded black polycarbonate (lexan) UV stabilised, which have sufficient elasticity to survive heavy impacts. Rotating shaft is Beryllium Copper fully hardened riding in a modified teflon, self lubricating bearing.Signal generated by a permanent Indox magnet influencing a Hall effect switch with square wave output, linear variation of frequency with speed. Startup speed (threshold) 1.75mph,operating temperature -55°C to +60°C, Free of ice. Weight: 400g. Flexible boot. protects electrical connections.Range 0-250 mph. The positioning of the sensor is critical to the accuracy, all obstructions, ie buildings/trees, higher than the positioning of the sensor must be three times the height distance away. More Information.

Windspeed Interpretation
Wind Run - incorporated into the Wind Direction HTML graph, distance wind has travelled in a given time period. Useful for determining the movement of pollution from an industrial process.

Windspeed Now - gated over a moving 3 second window period.

Two and Ten minute average - allow easier interpretation of wind speed from its volatile nature. Quick reference online Windspeed average and Gust / Peak HTML graphs are generated.

Gust gust / peak value - in any given second with time at which this occurred to the nearest minute, sampled 1 times per second, giving overall daily maximum gust and are reset once per 24 hours usually at 23:45. Direction of gust can be recorded if required. Historical records are examined to display an overall maximum windspeed value for the last 48 hours or other period. In addition a max gust value over the last 20 minutes is given. Sensor requires no maintenance.

Wind movement is also represented as a force value using the Beaufort scale giving a number between 0 and 12 with a description on conditions ranging from Calm to Gale. When Knots are selected, the conditions are described in terms of sea conditions and probable wave heights.

Wind Chill is calculated using Air and Windspeed.

Wind Direction

Direction Sensor vane UV-stabilised black ABS plastic. Stainless Nose. points into the wind providing direction the force is coming from. Interpreted by a conductive plastic potentiometer, with stainless shaft & bearings. Requires a force greater than 1 mph and has a linear movement around 360°. Signal is a DC voltage from wiper of potentiometer. Using <1mA current, operating in -55°C to +60°C free of ice conditions. Weight 100g, Flexible boot. protects electrical connections.Range 0-250 mph.

Direction Interpretation
Direction information is divided into 16 points, each sector covering 22.5°. As wind movement is volatile, the sensor is sampled 3 times per second and an impression of direction built up using 16 totalisers. At every display interval the largest total dictates the direction of wind. Combined with Windspeed information, a polar plan of wind movement can be determined for the locality. Wind distribution thru' out the sectors is displayed in the Analysis section of real time data and represented as the run of wind in each direction on the trend graphics.

Rainfall

Rainfall catchment area is 200mm into a funnel and tipping bucket mechanism, self emptying, each tip represents 0.1mm actuating a reed switch using a magnet.. Maximum of 50mm per hour. Low maintenance - check for leaves after autumn. Non heated. Can be heated in colder areas. 190mm height.

Rainfall Interpretation
Precipitation (non frozen) is totalled and displayed as millimetres. Total is stored for each interval usually 3 times per hour. With Air temperature information will display output as rainfall, sleetfall or snowfall. Current data is shown as rainfall total daily and historically over last 3 days (default) or longer periods if required. An online chart recording type Rain HTML graph is also available.

Barometric Pressure

Signal conditioned absolute pressure transducer. 800 - 1100 mBar. Calibrated & temperature compensated.The output voltage generated is directly linearly proportional to the barometric pressure range. Operating temperature -40 to +85°C, temperature compensated -10 to +60°C. Linearity and Hysteresis.. Typically 0.005 to 0.1 % Full Scale Offset. (refering to best straight line fit measured for offset pressure, full scale and half scale pressure.). Temperature shift -10 to +60°C.typically 0.05 to 0.3 % FSO/10°C, response time 1 millisecond. Pressure reading is aways set to read the pressure at sea level, compensation is added to sites above or below.A maximum working height allowable for the sensor is 1270 metres above sea. Accuracy: ±0.3 millibars over the range 948 to 1050mB.

Pressure Interpretation
Can show the arrival of stormy or calmer weather conditions, Now, Maximum and Minimum are captured with time occurance. Rising, Falling and Steady analysis is derived from examining records 1 hour or more prior . Pressure HTML graphs indicate trend in addition to high resolution graphs generated from stored data. "mBars" also know as millibars is the same as hecto pascals hPA.Pressure related to sea level is also known as QNH, used by the aircraft industry, the pressure 'reduced' to mean sea level, an altimeter set to the airfield QNH reads the elevation of the airfield when on the ground. Barometer changes can be used to detect problems within certain landfill sites where internally generated gases such as Methane can be released and concentrated due to rapid pressure jumps.

Solarimeter

Visible wavelength photo diodes providing a sun intensity value which can be calibrated to Watts per metre sq, but generally provides light level conditions. The HTML graphic trend produced shows a point at which light is at sunshine intensity (orange) and no direct solar energy within the grey areas.

Interpretation.

The sensor is calibrated to provide sunlight hours (also displayed as minutes) and html graphics showing daylight and sunlight separations.

External Sensor Platform

The Platform is generally positioned at the highest location possible to avoid wind obstacles such as trees or other tall buildings. The ideal height is 10 metres. The instruments are held via a 50mm x 3m mast to a side wall using brackets. Two signal cables (6mm dia) foil shielded feed back to the weather station interrogation unit.