1. Overview

The rod type soil moisture temperature conductivity observation system uses sensor tube insertion contact measurement to obtain soil indicators. Common rod type soil moisture observation belongs toFDR (Frequency Domain Reflectance) method. Newly developed by Campbell Corporation in the United StatesThe SoilVUE10 TDR tubular soil three parameter sensor adoptsTDR time domain reflectometry method.

Firstly, let's understand several quantities of soil moisture:

The forms of water in soil are solid water and gaseous water

Field water holding capacityIt refers to the soil moisture content when a large amount of capillary water is suspended in the soil without being affected by groundwater.

soil moisture contentGenerally refers to the excellent soil moisture content, i.e100gDried soil contains several grams of moisture, also known as soil moisture content.

These indicators are closely related to the type of soil, and the general types of soil are as follows:

Typical soil moisture content:

The movement and storage of soil water:

2. Measurement method for soil moisture content:

TDR(Time domain reflection method

TDRIt is based on the different transmission times of electromagnetic waves emitted by the detector in materials with different dielectric constants,And calculate the moisture content of the tested substance. The propagation speed of electromagnetic waves is closely related to the dielectric constant of the propagation medium,However, there are significant differences in the dielectric constants of soil matrix, water, and air(20At ℃,The dielectric constant of water is80,The dielectric constant of air is1,The dielectric constant of dry soil is between3～7)Therefore, changes in soil moisture content have a significant impact on the dielectric constant,Thus, the propagation speed of electromagnetic waves,You can determine its moisture content.

FDR(Frequency domain reflection method

FDRSoil moisture monitoring instrument is a type of instrument that utilizesLCThe oscillation of a circuit is determined by measuring the dielectric constant of a medium based on the changes in the oscillation frequency of electromagnetic waves in different mediaε, and then deduce soil moisture through a certain corresponding relationshipθvThe instrument.

3. EnviroPro Rod Soil Moisture Temperature Conductivity SensorEP100G

Soil moisture resolution: 0.01%

Soil salinity resolution: 0.001 dS/m

Soil temperature resolution: 0.01 °C

Soil moisture accuracy: +/- 2% @ 0% VWC to 50% VWC

Soil salinity measurement range: 0 to 6 dS/m*2

Soil salinity accuracy: +/- 5% @ 0 to 4 dS/m

+/- 5% @ 10% to 30% VWC

Soil temperature accuracy: +/- 1 °C @ 25 °C

signal output: SDI-12

power supply: + 6 to +15 VDC

working temperature: - 20 to +60 °C

power waste:0.1mAstatic state 1mAmeasure/Single measuring point

Distance between measuring points: every10cm per layer

Model selection:EP100G-04（4 measuring points);EP100G-08 (8 measuring points);EP100G-12 (12 measuring points);EP100G-16 (16 measurement points)

4. Stevenson rod type soil moisture temperature sensorGroPoint Profile

Soil moisture:

Measurement range:0-100%

Accuracy:0.5%

Soil temperature:

Measurement range:-20°C to +70°C

Working temperature:-40°C to +85°C

Accuracy:±0.5 °C

Signal output:SDI-12(RS-485)

Power supply:6 -14 VDC,*Big18 VDC

Waterproof:IP66/IP68

Sensor measurement spacing: every15cm per layer

Model selection:

GroPoint Profile 2（2nd layer measuring points)

GroPoint Profile3 (3-layer measuring points)

GroPoint Profile4 (4th floor measuring points)

GroPoint Profile5 (5th floor measuring points)

GroPoint Profile6 (6th floor measuring point)

GroPoint Profile8 (8th floor measuring point)

5.SOILVUE10-Pipe typeTDR Soil Moisture Sensor

SoilVUE ™ 10 is the United StatesThe integrated profile TDR soil moisture sensor developed by Campbell Company adoptsTrueWave ™ TDR technologyDesigned specifically for environmental researchers and monitoring networks, it canSimultaneously measuring soil moisture at multiple measurement points on a profile、temperature、conductivity.abouthaveFor researchers with similar needs，SoilVUE ™ The emergence of 10 is a noteworthy selection.

Exclusive to Campbell Science CompanyTrueWave ™TDRtechnologyUsing the best optionThe rise time of the waveform and advanced waveform analysis techniquesdeterminationThe actual travel time of high-frequency pulses. This processrealizationHigh Resolution, can obtainSmooth measurement signal,be better thanotherTDR measurementTechnology,Not all based onTDR sensors are capable ofgetEqually good measurement results.

Technical features and advantages

lOne sensor can measure simultaneouslySoil moisture, dielectric constant, electrical conductivity, and soil temperature for 9 layers (1-meter specification) or 6 layers (0.5-meter specification).

lsimpleeasyQuick installation.

lVersion 1.4 SDI-12 output signal, compatible with most data collectors.

lSpecially designed for long-term outdoor installation.

detailed description

SOILVUE ™10 is composed of TDR circuits connected to six or nine spiral waveguides, forming part of the entire threaded design. The built-in single sensor in the thread design improves the contact between the sensor and the soil, reducing potential errors caused by air gaps. The TDR circuit generates short rise time electromagnetic pulses for spiral waveguides, calculates the dielectric constant of the surrounding medium using the bidirectional travel time of the applied pulse, and determines the volumetric water content using a hybrid model.

The soil moisture profile sensor can be used with standardDrill holes with a 5cm diameter hand drill for installation. No need for mining machinery or expensive customized tools.

Waterproof grade is used between the cable and the sensorIP67 aviation plug connection, easy to replace.

6. Application of Soil Moisture Station:

Important guarantee for data quality control and rationality inspection

Realize unified data management

Convenient for users at all levels to use and manage

No need for a fixed computerNo need to install special software

Save on-site collectionHuman and material resources for data management

Working principle diagram:

•Building a basic data platform at the bottom level

•Building an application system based on the WebGIS (Sky Map) platform

•Divide the application system into front-end and back-end, with the front-end (homepage+central station page+local station page) used for application display and the back-end used for maintenance and management

•Support online browsing on PC or mobile (Android Baidu Browser, Mobile UC Browser) anywhere with internet access

Soil moisture station management platform:

Wireless transmission function:

Interface display

The login interface includes options such as homepage, data, warning, announcement, management, and help. You can directly query the data information of a certain time, a certain site, or a sample site.

Enter the "Data" option, and the site is located on the left side of the interface. Drop down options for sample plots, with time options on the right, allowing for detailed observation of data lists, line charts, statistical data, and other information for a certain site sample plot at a certain time, and exporting. csv files for the selected time and sample plot.

Data line chart:

Data List:

Soil Moisture Observation System Data Management Platform

Data transmission and management

Interface display:

Entering the "Warning" interface, you can clearly see the sites and sites with communication abnormalities.

The "Management" interface has options for "User Management", "Threshold Management", "Monitoring Station Information", "Historical Data", "Announcement Management", and "Data Reporting Management" on the left side of the homepage. On the right side of the homepage are all "System Administrators" and "Station User Information"

In the "Monitoring Station Information" interface, system administrators can modify and view site and plot information.

In the "Announcement Management" interface, system administrators can add announcements and view announcement information

Data information can be reported in batches by year and time period. System administrators can view and delete reported data informationWaiting for management.

7. References:

1.Dynamic analysis of soil moisture growth season in semi-arid loess hilly area-Xu ZhiyaoZhang Qindi, Yang Lei

2.Study on the Water Transport Law of Different Soil Types-Wang Suyu

3.Optimization deployment method for soil moisture monitoring based on effective high moisture content-Wang Shan,Hu Zhenhua

4.Research progress on temporal stability of soil moisture-Lin PengfeiZhu Xi, He Zhibin

5.The fluctuation of soil moisture on alpine grassland ecosystemThe impact of CO2 and N2O emissions-Wang Rui,Wang Ping, Gao Yongheng