Classification of soil moisture sensors
After more than half a century of development, soil moisture sensors have been in various types and forms. The measurement of humidity has a certain degree of complexity. And the well-known hair hygrometer, wet and dry bulb hygrometer, etc. Can no longer meet the actual needs of modern requirements. Therefore, various soil moisture sensors have been developed. What kind of soil moisture sensor best.
Capacitive soil moisture sensor
The sensitive element of the capacitive soil moisture sensor is a humidity sensitive capacitor. And the main materials are generally metal oxides and high molecular polymers. 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 soil moisture sensor best to detect soil moisture .
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).
In order to obtain good moisture sensing performance. It is hoped that the closer the two levels of the capacitive soil moisture sensor. The greater the change in the active area and the dielectric constant of the moisture sensing medium, the better. Therefore, a sandwich-type capacitive soil moisture sensor is usually used. Its advantage is that it can make the two levels of the capacitive soil moisture sensor closer. Thereby improving the sensitivity of the capacitive soil moisture sensor.