Domestic Capacitive Sensor Chip Applied in Water and Soil Moisture Detection

The determination of soil moisture content refers to the quantitative determination of various liquid moisture in the soil. Sometimes it also includes ice and some mineral crystal water, which can be generally divided into two categories: sampling method and in-situ determination method. The sampling method is to measure the moisture content of the soil sample after sampling in the field, and the in-situ measurement method is to directly measure the soil moisture content in the field using instruments and equipment.

Agriculture is the foundation that supports the construction and development of the national economy. To do a good job in agricultural development, we must pay attention to fertilization and soil improvement, adjust soil moisture, and promote agricultural development. For the sustainable development and regulation of soil moisture, soil moisture detectors can be used to detect soil moisture, providing a scientific basis for regulating soil moisture. Soil moisture is an important part of soil and plays a very important role in crop growth and water-saving irrigation.
Under the action of molecular gravitation, soil particles absorb water molecules in the air on their surface and become hygroscopic water. It is an extremely thin water film close to the surface of soil particles, which is aggregated by 15-20 layers of water molecules. There is a strong attraction between hygroscopic water and the soil, and it is the main component of soil water in the soil layer when the soil is close to the permanent wilting point of plants. Hygroscopic water is tightly bound on the surface of soil particles, close to the properties of solid water. Hygroscopic water has no ability to dissolve solutes, has extremely weak or even non-conductive conductivity, has a low freezing point, cannot flow in a liquid state, and cannot be absorbed by plant roots, so it is also called strongly bound water.
Soil hygroscopic water can also refer to the part of the moisture that the fresh soil still contains after it has been dried under ventilated conditions for 1 week and stabilized. Since the soil analysis is based on the dry quality of the soil, and the hygroscopic water can be removed at a high temperature of 105°C, the hygroscopic water is generally measured while measuring the physical and chemical properties of the soil.
Moisture is the main factor determining the dielectric constant of soil. Measuring the dielectric constant of soil can directly and stably reflect the real moisture content of various soils. The principle of on-site testing of soil moisture - frequency domain reflection principle (FDR): the instrument emits electromagnetic waves of a certain frequency, the electromagnetic waves are transmitted along the probe, and return after reaching the bottom to detect the output voltage of the probe. Since the change of the soil dielectric constant depends on the soil Water content, the water content of the soil can be calculated from the relationship between the output voltage and water.