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The leaf wetness sensor is a plant surface humidity measurement instrument widely used in greenhouses, laboratories, farms, artificial climate chambers and other environments. The instrument is compact in size, stable in performance and high in sensitivity, and adopts analogue form for accurate measurement. It is popular among researchers in modern agricultural research. Leaf surface wetness sensor is to promote the development of precision agriculture is an important basis for the use of the instrument can understand the growth and development of crops and crop growth research; prevention of pests and diseases and early warning; foliar fertiliser, spraying, spraying and irrigation control, etc., is the observation and research of foliar humidity, prevention of pests and diseases and sprinkler sprinkler control of an important tool, so how does the foliar wetness sensor do accurate measurement of the How does the foliar wetness sensor measure accurately? What is the working principle of the leaf surface wetness sensor?

In terms of composition, the leaf wetness sensor is mainly composed of a leaf analogue panel, a signal processing circuit, a temperature correction circuit, a potting shell and other parts. In the process of measurement, its internal processor will treat the entire leaf panel as a dielectric constant medium to measure, through the high-frequency signal source and its processing circuit to achieve the measurement of humidity information. In order to prevent the influence of temperature and drift, the internal temperature correction and signal drift compensation circuits are also used to achieve accurate and reliable measurement.

The above is the working principle of the leaf surface wetness sensor. It is worth saying that the leaf surface wetness sensor belongs to a very precise device, so the user in the process of use, some places still need to pay attention to, such as the use of the process, please do not disassemble, with sharp objects or corrosive liquids in contact with the sensor indicates that in order to avoid damage to the product, and do not arbitrarily change the product has been welded at the time of delivery of the components or guides to ensure that leaf surface wetness sensor Stability and accuracy of use.

Water vapour evaporates from the leaf surface to the periphery of the leaf through open stomata and epidermal conductance pathways, so that a water vapour concentration gradient across the critical layer is formed. The humidity measured by the leaf surface wetness sensor in the immediate vicinity of the leaf surface depends on it. In still air, the absolute humidity in the critical layer is not equal to the value obtained by conventional measurements at some distance from the leaf surface (e.g. at the top of the crop or in a standard meteorological shed).

A practical method for determining water vapour pressure in the immediate vicinity of the leaf surface has so far been through foliar moisture sensors. If a measuring instrument is installed on or near the leaf surface, the critical layer itself changes and the measured values are not reliable. Measurement of the humidity on the leaf surface by means of a leaf surface wetness sensor reports the humidity conditions between 3 mm and 30 mm from the leaf surface. Accurate measurement of humidity within 3 mm of the leaf. In conclusion, the use of foliar moisture sensors is feasible for tightly controlled laboratory conditions.

The wind across the foliage becomes laminar and the industry takes water molecules directly from the foliage or else the wet bulb changes the humidity in the critical layer. This naturally has an effect on the surface measurements of the foliar wetness sensor. At the same time, the wet and dry bulb method requires that the wind speed through the wet bulb is greater than the wind speed that destroys the critical layer. Therefore, to accurately measure humidity values at the leaf surface, the past method is not appropriate.

Due to the limitations of the commonly used methods in the past and certain shortcomings and can not really meet the leaf surface humidity measurement, so far the development of the leaf surface wetness sensor in the use of not only convenient, for the experimental determination of the data results are more accurate compared to some traditional methods, so the leaf surface wetness sensor in other areas of the application will gradually increase, and will not be confined only to the determination of agricultural crops.