Shed the principle and method of reading of the thermometer

Japan and Europe and the United States in the early 50 s application of greenhouse film mulching hotbed for success, then cover the shed and greenhouse also obtain good effect. In the autumn of 1955 the introduction of PVC agricultural film in China, the first in Beijing used to shelter cover vegetables, obtained the effect of the early production. Greenhouses are vegetable production of special equipment, with the development of production greenhouses used more widely. The greenhouses have been used to potted flower and the cultivation of cut; Fruit production for cultivation of grapes, strawberries and watermelon, melon, peach and citrus, etc. ; Forestry production for the cultivation of forest tree seedlings, ornamental trees, etc. ; Breeding for sericulture, chicken, cattle, pigs, fish, fish, etc. And there are to be used together with greenhouses greenhouses thermometer, also known as the maximum and minimum thermometer, it is mainly used to record in a day or a period of time the maximum temperature and minimum temperature in the air. The general measurement range is - 40+50C。 It works, within about two stick of glass wool stoma were blue indicating needle, when the temperature changes, the blue indicator needle by mercury push up; When the temperature drops, the blue indicator needle changes influenced by temperature drop; Thus indicates the maximum and minimum temperature. As shown in the left of the indicating needle to the lowest temperature, the right of the instruction pointer is the highest temperature. Maximum and minimum thermometer reading method is: the left number: the above red is minus temperature to the right of the said values: the following red values are below zero temperature.