Thermometers

Thermometer - An instrument used to measure temperature. Our traditional thermometers are either a closed, graduated glass tube in which a liquid (coloured alcohol) expands or contracts as the temperature increases or decreases or the easier to read bimetallic dial thermometer in which the dial is actuated by different thermal expansion of a narrow stip of two different metals bonded together and coiled in a spiral. All have been calibrated by the maker. Digital thermometer provide a great degree of accuracy and like their traditional counterparts need to have their outdoor sensors protected from direct sun to ensure this degree of accuracy. 

Hygrometer - An instrument used to measure relative humidity.