What are the display modes of the soil moisture sensor?

The soil temperature and humidity recorder is composed of two sensors, namely the soil moisture sensor and the soil temperature sensor. It is precisely because multiple sensors can be connected that multiple parameters can be measured simultaneously. 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 is divided into two categories according to the display method: one is the direct display method, and the other is the secondary sensing method.

Direct display mode: Direct display mode can be divided into three types:

One is the display type with suction negative pressure gauge (also known as negative pressure tensiometer);

The second is the electric contact vacuum meter display type, which is often used for alarm type moisture sensors;

The third is to use the U-tube mercury column display type. Among the three direct display methods, the U-shaped mercury column display type has the highest accuracy, the most accurate reading and the smallest error, and can be accurate to millibars. The disadvantage is that in the use of farmland, when the U-shaped pipe is broken, the mercury will pollute the farmland and cause environmental pollution. The choice of the three display modes is often selected according to the specific requirements of the user.

Secondary sensing display mode: 

The secondary sensing display type is to convert the pressure reading in the direct display sensor into the moisture content. For example, the mercury indication part of the U-shaped tube can be replaced with a piezoresistive sensor as the secondary sensing The digital soil moisture measuring device can be digitized and directly display the soil suction value of the sensor. Secondary sensing can also be used for remote measurement of soil water potential. For example, the soil water tensiometer (sensor part) is buried in the soil depth required in the field, and the negative pressure suction of soil water is transmitted through the penetration of the water film in the porous clay probe. , make the moisture sensor generate negative pressure, this negative pressure is transmitted to the piezoresistive sensing current transmission secondary sensor, and an electrical signal is given, which is transmitted to the remote telemetry thermometer through the wire, and can be transmitted to the computer by the interface line, so as to complete the Telemetry of soil water potential in the field. However, the 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 cannot be measured under the high suction.

The sensor method to measure soil moisture has the advantages of in-situ measurement in the field, fast direct reading, no damage to soil structure, low price, no radioactive substances, safety and reliability, and it is convenient for long-term observation and accumulation of field water potential data. In particular, the secondary sensor has the advantages of digitization, and can be connected with the computer interface, so that the soil moisture measurement can be automatically monitored. This modern measurement method has become a new trend in the research of soil moisture measurement methods.

Agriculture Sensors Catalog

Agriculture-Sensors-Catalog-NiuBoL-2024.pdf