The important basis of outdoor air in greenhouse is to look at thermometer, and the accuracy of temperature measurement is directly related to whether vegetables are in an environment suitable for growth. In order to read the temperature conveniently, some vegetable farmers only set a thermometer at one end near the shed door, which is not desirable. Because the temperature near the shed door is relatively low, if the vent is adjusted according to the displayed temperature, it will inevitably lead to the high temperature in the shed and affect the normal growth of vegetables.