test methods
Fundamental
advantage
Shortcomings
Remote Sensing
The reverse electromagnetic wave intensity of soil with different water content is different
Large range of measurements
Only a few centimeters of soil below the ground can be measured and based on fixed-point measurement data, the accuracy of measured data is not high.
GPR method
The propagation speed of electromagnetic waves in soil corresponds to the dielectric constant of soil
Larger measurement range
Only a few centimeters of soil below the ground can be measured and based on fixed-point measurement data, the accuracy of measured data is poor
Drying method
The soil was dried at about 105°C, and the moisture content was directly calculated to determine the soil moisture content.
Low cost, simple, high accuracy
It takes time and effort, and destroys the soil at the measurement point, which is not conducive to in-situ measurement. The sampling process will cause evaporation error.
Neutron moisture meter
Calculate soil moisture measurements by recording the number of fast neutrons that have similar mass hydrogen atoms as slow neutrons
Representative, high accuracy of measurement data, moderate instrument prices
The measured slow neutron number depends on the conversion of the standard curve to water content. The calibration process will introduce errors and have radiation hazards.
Time domain reflectometry
The propagation speed of electromagnetic waves in soil medium corresponds to the dielectric constant of soil
Quick and accurate, continuous automatic monitoring of in-situ soil
Measurements need to be corrected and expensive
Γ-ray method
When γ-ray penetrates the soil, the degree of energy decay corresponds to the soil moisture content.
Fast, accurate, continuous automatic monitoring of soil measurements
Affected by the dry density of the soil, only suitable for laboratory determination
Tension meter method
The negative pressure of the negative pressure tube corresponds to the soil suction
Cheaper, simpler operation for long-term monitoring of in-situ soils
Affected by the temperature, it will fail when the soil moisture content is low, and the water in the negative pressure will bring error to the soil.
Dew point microvoltmeter method
The temperature of the thermocouple probe is measured by the electrical method, and the linear function that the specific temperature is the water potential of the measured interval is discussed.
It can measure the low soil water potential and can measure long-term monitoring value of in-situ soil
Affected by temperature changes very much, the measurement error is very high when soil moisture is high
Resistance method
Resistance changes correspond to surrounding soil water potential
cheap price
Sensitive to soil type, salt concentration and soil temperature, the measurement range varies with different resistance blocks
Professional measuring instruments (multifunctional soil moisture recorder, multi-point soil moisture monitoring system)
Using sensors to measure soil moisture
Real-time monitoring of soil moisture changes and curve analysis of measurement results
The result of the measurement is influenced by the salinity in the soil
Now more commonly used measurement method is to use measurement soil moisture thermometer to measure, but there is also a measurement method is also used more, that is the soil moisture monitor designed based on the principle of FDR, this measuring instrument performance and FDR is similar, but it is cheaper than him.Activated Alumina,Activated Alumina Balls,Alumina Desiccant,Alumina Adsorbent
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