A Small Single Stevenson Screen (Stevenson screen) is an enclosure to shield meteorological instruments against precipitation and direct heat radiation from outside sources, while still allowing air to circulate freely around them. It forms part of a standard weather station. The Stevenson screen holds instruments that may include thermometers (ordinary, maximum/minimum), a hygrometer, a psychrometer, a barometer and a thermograph. Its purpose is to provide a standardised environment in which to measure temperature, humidity, dewpoint and atmospheric pressure. It is manufactured from teakwood material as dimensions strictly as per IS:5948-1970 specifications. All the four sides are double louvered, roof is double and the floor consists of overlapping boards seperated by an air space. The front door is hinged at bottom and provided with two chains so that it comes to rest in an approximately horizontal position when opened to its full extent. The screen itself supported on four legs.
Thermometer screen comes with steel stand height such that the floor of thermometer screen will be exactly 117.5 cm above the ground ( at the eye site level). The steel legs are made from MS angles duly coloured & marked with different colour for foundation level
There are two types of Screen available Small size (Single) Thermometer Screen(Internal size between louvers : 560 x 315 x 412 mm)
Generally it is used for placing separate glass thermometers :
Dry Bulb thermometers
Wet Bulb thermometers.
There is vertical wooden platform for mounting these four thermometers on it.
Big size (Double) Thermometer Screen (Internal size : 1355 x 355 x 345 mm)
Generally it is used for placing Thermograph, Hygrograph or Barograph inside it.
The Sunshine Recorder is used for the accurate measurement of the duration of bright sunshine at a place. The sunshine Recorder consists of a glass sphere mounted concentrically in a section of a spherical bowl. Three overlapping grooves are provided in the bowl to take cards suitable for different seasons of the year. The instruments are mounted on heavy base, The scale of degree of latitude from -5 to 45 Degree. The sphere support with the glass sphere and bowl can be tilted, adjusted and clamped at an angle to suit the latitude of the station. The focused Sun’s rays burn a trace on the card to indicate the period of bright sunshine during the day.
The glass sphere has a focal length of 74.9 mm and having deviation of +/- 0.25 mm. The base of the instruments is good quality marble stone.
The card used in the instrument is made from white pasteboard and has a thickness in between 0.43 mm to 0.48 mm. There are three types of card used in the instrument, namely Straight, Curved Short and Curved Long. The upper surface of the card is colored to a standard shade of the blue/dark gray colour. The instruments is supplied with one year cards.