GB/T 33705-2017 in English

In-depth interpretation of the national standard for frequency domain reflection method for soil moisture observation

1. Overview of the standard

The National Standard of the People's Republic of China GB/T 33705-2017 "Frequency Domain Reflection Method for Soil Moisture Observation" specifies the observation items, site selection requirements, instrument requirements and observation steps for observing soil moisture using the frequency domain reflection method. This standard applies to the construction, operation and maintenance of automatic soil moisture observation stations using the frequency domain reflection method.

2. Observation principle and technical background

Frequency domain reflection is a method of measuring soil moisture content by using the change in the frequency of electromagnetic waves based on the difference in dielectric constants between water and other dielectrics in the soil. This method accurately measures the volumetric moisture content of the soil through the frequency change of the electromagnetic waves emitted by the sensor in materials with different dielectric constants, and derives parameters such as weight moisture content, relative humidity and effective water storage.

3. Site selection requirements

4. Instrument requirements

5. Observation steps

1. Parameter setting:Includes input of site information and soil moisture constant.
2. Data collection:Read once every 1 minute, and average every 10 measurement results as the observation value.
3. Data processing:Calculate the derived quantities such as weight moisture content and relative humidity according to the formula.
4. Data storage:It is recommended to store hourly data, and the length of time is determined by business needs.

6. Implementation suggestions

In actual applications, instruments and equipment should be checked regularly to ensure their normal operation. Especially when the soil volume moisture content measurement results are abnormal, it is necessary to check the communication lines and equipment status in time, and perform annual maintenance and calibration in accordance with standard requirements.

7. Conclusion

GB/T 33705—2017 provides a scientific and technical basis for soil moisture observation, ensuring the accuracy and reliability of data. By selecting a reasonable site, using high-performance instruments and standardizing operating procedures, the overall level of soil moisture monitoring can be effectively improved.