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Product Name: Soil Moisture Meter / Tester
Product model: Soil moisture temperature measuring instrument (TZS-IIW), Timely positioning soil moisture measuring instrument (TZS-II), such as soil moisture meter (GMK-770S), soil moisture meter/meter/meter (TZS ), pen-type soil moisture meter (BS-30, BS-40) and more, please see http://
Six methods for testing soil moisture and comparisons:
Accurate determination of soil moisture is of great importance in guiding agricultural production and soil water research. There are many ways to measure soil water, which are summarized here in six ways:
(1) Drying method: Also called weight determination method, that is to take the soil sample into the oven and dry it to constant weight. At this time, the free water in the soil moisture is lost in the form of steam and the weight is weighed to obtain the soil moisture content. Drying methods include infrared, alcohol burning, and oven methods.
(2) Neutron method: the neutron source is buried in the soil to be measured, the neutron source continuously emits fast neutrons, the fast neutron enters the soil medium and collides with various atomic ions, and the fast neutron loses energy, so that It slows down. When fast neutrons collide with hydrogen atoms, the energy loss is greatest, and it is easier to slow down. The higher the moisture content in the soil, the more hydrogen atoms there are, and the greater the density of slow neutron clouds. The neutron meter determines the water content in the soil by measuring the relationship between the density of the slow neutron cloud and the water molecules.
(3) γ-ray method: Similar to the neutron instrument, the γ-ray transmission method uses 137Cs as a radioactive source to emit γ-rays, and the probe receives the energy of γ-rays transmitted through the soil, and is converted with the soil moisture content.
(4) Soil Moisture Sensor Method: Currently used sensors are various, including ceramic moisture sensor, electrolyte moisture sensor, polymer sensor, piezoresistive moisture sensor, photosensitive moisture sensor, microwave moisture sensor, and capacitive moisture sensor.
(5) Time Domain Reflectometry: The Time Domain Reflectometry (TDR) method, which is based on the propagation of electromagnetic waves in a soil medium, the decay of conduction constants such as velocity depends on the nature of the soil, especially on the water content in the soil and Conductivity.
(6) Frequency domain reflectometry: The FDR (Frequency Domain Reflectometry) method measures the volumetric content of soil moisture by measuring the change in electrolyte constants. These changes are converted into millivolt signals proportional to soil moisture. For example, the British-made Thetaprobe moisture measurement uses this technology. Its advantage is high measurement accuracy and low price. It can measure single-point or multi-point vertical sections.
Method comparison:
Drying method
Neutron method
Γ-ray method
Soil moisture sensor method
Time domain reflectometry and frequency domain reflectometry
Simple and intuitive, but the measurement does not have continuity. And sampling will interfere with the continuity of soil moisture in the field. The sampling holes left in the field will cut off some roots of the crop and affect the movement of soil moisture;
The neutron method can be periodically repeated at different depths in situ without destroying the soil, but the vertical resolution of the instrument is poor, surface measurement is difficult, and radiation hazards are healthy.
The gamma ray method and the neutron meter method have many advantages, and they have higher vertical resolution than the neutron meter, but the gamma ray also harms human health.
The accuracy of the sensor method for measuring soil moisture is affected by the design of the sensor, process manufacturing, etc. It is still in the further development stage.
The frequency domain reflectometry method and the time domain reflectometry method are the most commonly used. They all have the advantages of mature technology, high precision, and portability. Compared with TDR, FDR has more unique advantages in terms of moisture measurement methods because it has more stability, is less affected by salt, is more energy-efficient, has less limited cable length, can be continuously measured in situ, and has no radiation. British DELTA-T company is the originator of the global production of FDR soil moisture meter, has been leading the front of science and technology in the field of soil moisture measurement for more than 30 years, the products are widely used in more than 60 countries and regions.
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