The soil temperature and humidity sensor is composed of two sensors. Namely a soil moisture sensor and a soil temperature sensor. The soil temperature and humidity sensor is related to the growth of crops and is the basis of farmland operations.

The soil temperature sensor is a soil temperature sensor that can monitor the temperature of the soil. The atmosphere and the water, and is used in experiments and scientific research. The soil temperature is closely related to the growth and development of crops. The decomposition of fertilizers and the accumulation of organic matter. It is an important environmental factor in agricultural production. Soil temperature is also an extremely important factor in the formation of microclimate. So the measurement and research of soil temperature is an important part of microclimate observation and agrometeorological observation.

Soil moisture sensor is also known as: soil moisture sensor, soil moisture sensor, soil moisture sensor. It is mainly used for measuring soil volumetric water content, monitoring soil moisture, agricultural irrigation and forestry protection.

Capacitive soil moisture sensor

The sensitive element of the capacitive soil moisture sensor is a humidity sensitive capacitor. And the main material is generally metal oxide and high molecular polymer. These materials have a strong adsorption capacity for water molecules. And the amount of water absorbed varies with the change of environmental humidity. Because water molecules have a large electric dipole moment. The permittivity of the material changes after water absorption, and the capacitance value of the capacitor also changes. The change of the capacitance value is converted into an electrical signal, and then the humidity can be monitored. Humidity-sensitive capacitors are generally made of polymer film capacitors. When the environmental humidity changes, the dielectric constant of the humidity-sensitive capacitor changes, and its capacitance also changes. The capacitance change is proportional to the relative humidity. This feature can measure humidity. The humidity sensing media of commonly used capacitive soil moisture sensors mainly include: porous silicon. Polyphthalimide, in addition to polysulfone (PSF), polystyrene (PS), PMMA (linear, cross-linked, plasma polymerization).

Resistance type soil moisture sensor

The sensitive element of the resistive soil moisture sensor is a humidity sensitive resistor. And its main materials are generally dielectrics, semiconductors, porous ceramics, etc. These materials have a strong adsorption of water. After absorbing moisture, the resistivity/conductivity will change with the change of humidity. So that the change of humidity can cause the change of the resistance of the humidity sensitive resistor. And the change of the resistance can be converted into the required electricity. Signal. For example, an aqueous solution of lithium chloride forms a thin film on the substrate. As the water vapor content in the air increases or decreases, the thin film absorbs moisture and dehumidifies. The salt concentration in the solution decreases and increases. And the resistivity increases and decreases accordingly. The resistance between the two stages increases and decreases. Another example is the porous ceramic humidity sensor. The ceramic itself is composed of many small crystal particles. And most of the pores are in communication with the outside world. The pores can absorb water molecules and cause changes in ion concentration. Which leads to changes in resistance between the two poles.

Ionic soil moisture sensor

Ion-sensitive field effect transistor (ISFET) is a semiconductor biosensor, which was developed by P. Invented by Bergeld. The ISFET directly contacts the ion buffer solution in the measured solution through different sensitive film materials on the grid. And then the ion concentration in the solution can be measured.

The schematic diagram of the structure model of the ion-sensitive soil moisture sensor is shown in the figure below. Ion sensitive devices are made. The ion selective membrane (sensitive membrane) and the converter are composed of two parts. The sensitive membrane is used to identify the type and concentration of ions. And the converter converts the information sensed by the sensitive membrane into electrical signals. The ion-sensitive field effect tube makes a layer of sensitive film on the insulating grid. And the types of ions detected by different sensitive films are also different, so that it has ion selectivity.