Soil temperature and humidity recorder is composed of two sensors, namely soil moisture sensor and soil temperature sensor. It is precisely because multiple sensors can be connected that multiple parameters can be measured at the same time. The multi-point soil temperature and humidity recorder is the most important instrument in soil testing instruments. Soil testing instruments are related to the growth of crops and are the basis of farmland operations. The moisture sensor can be divided into two categories according to the display mode: one is the direct display mode, and the other is the secondary sensing mode. Steel Frame, Platform and Stairs for Boiler: Spare Parts,Slant Fin Boiler,Central Boiler Parts,Boiler Pressure Parts Jinan Boiler Group Co., Ltd. , https://www.jinanboilergroup.com
Direct display mode: The direct display mode can be divided into three types: one is the suction negative pressure gauge display type (also called negative pressure tension gauge); the second is the electrical contact vacuum gauge display type, which is commonly used in the alarm type moisture sensor; U-tube mercury column display type. Among the three direct display methods, the accuracy of the U-shaped mercury column display is the highest, the reading is the most accurate, the error is the smallest, and it can be accurate to the millibar. The disadvantage is that in the use of farmland, when the U-shaped pipe breaks, mercury will pollute the farmland and cause environmental pollution. The choice of three display modes is often selected according to the user's specific requirements.
Secondary sensor display mode: The secondary sensor display type converts pressure readings from direct display sensors to moisture content. For example, the U-tube mercury indicator can be replaced with a piezoresistive sensor as a secondary sensor. The digital soil moisture measuring device can realize digitization and directly display the size of soil suction value of the sensor. Secondary sensing can also be used to remotely measure the soil water potential. For example, a soil moisture meter (sensor part) is buried in the soil depth required in the field. The negative suction force of the soil water is transmitted through the permeation of the water film in the porous clay probe. The negative pressure is generated by the moisture sensor, and the negative pressure is transmitted to the piezoresistive sensor current and transmitted to the secondary sensor to give an electric signal, which is transmitted to the remote telemeter temperature meter through the wire, and can be transmitted to the computer through the interface line, thereby completing Soil water potential telemetry in the field. However, the use of a negative pressure tensiometer can only measure the low suction range. When the suction is high, the clay head will be “penetrated†by the air, so the soil water potential under high suction conditions cannot be measured.
The sensor method for measuring soil moisture has the advantages of in situ determination in the field, rapid direct reading, no damage to soil structure, low price, no radioactive material, safety, reliability, long-term observation, and accumulation of field water potential data. In particular, the secondary sensor has the advantages of digitization and can be interfaced with a computer to enable soil moisture measurement to be automatically monitored. This modern measurement method has become a new trend in the study of soil moisture measurement methods.
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Classification of different display methods for soil moisture sensors