Non-invasive TDR Probe Calibration for Soil Moisture
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Solution Overview
Problem
Existing calibration procedures for invasive time domain reflection probes are not suitable for non-invasive probes, as they fail to accurately account for the influence of the circuit board substrate on soil moisture and density measurements.
Innovation Solution
A non-invasive time domain reflection probe calibration method using mixed solutions of ethanol and deionized water to calculate the medium weight coefficient and waveguide length, and different concentrations of NaCl solutions to calibrate waveguide geometric dimensioning, along with compacted soil samples to establish correlation parameters for dielectric constant and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If invasive probes are inserted into the soil for testing, then the soil moisture content and density can be measured, but the insertion causes extrusion of the soil (squeezing effect) which generates test errors
Solution Approach 1:
The patent introduces a non-invasive probe that measures soil moisture and density through the ground surface without direct insertion. The probe uses electromagnetic wave propagation characteristics through an intermediate medium (the ground itself) to obtain measurement data, thereby avoiding the harmful squeezing effect while maintaining measurement capability
Solution Approach 2:
The patent replaces the mechanical insertion method with an electromagnetic field-based measurement method. Instead of physically inserting probes into the soil (mechanical system), the invention uses electromagnetic waves to penetrate and measure soil properties through the ground surface, eliminating mechanical disturbance to the soil structure
2Object-affected harmful factors
If non-invasive probes are used to avoid soil insertion, then the squeezing effect is overcome, but the calibration procedure becomes complex due to the need to eliminate circuit board substrate influence
Solution Approach 1:
The patent performs preliminary calibration actions by establishing reference measurement data under controlled conditions before actual soil testing. The calibration process pre-determines the relationship between electromagnetic wave characteristics and soil properties, storing these as reference parameters that simplify subsequent field measurements
Solution Approach 2:
The patent changes the calibration approach from complex multi-parameter adjustments to a simplified method based on electromagnetic wave propagation time and dielectric constant relationships. By focusing on key physical parameters (wave propagation characteristics, dielectric properties) rather than multiple geometric and material parameters, the calibration procedure becomes more manageable
3Ease of operation
If non-invasive probes with circuit board substrate are used, then probe insertion is avoided, but the substrate influence must be eliminated to achieve accurate soil moisture content and density testing
Solution Approach 1:
The patent extracts and separates the substrate influence from the measurement process. By identifying and isolating the circuit board substrate's electromagnetic characteristics, the calibration procedure removes its confounding effect from the final soil property calculations, leaving only the soil-related measurement signals
Solution Approach 2:
The patent applies partial calibration actions by focusing on the specific electromagnetic parameters affected by the substrate rather than attempting to control all possible variables. The calibration process addresses the substrate influence through targeted adjustments to wave propagation time and dielectric constant measurements, achieving sufficient accuracy without overly complex procedures
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables accurate calibration of non-invasive time domain reflection probes by determining the medium weight coefficient and waveguide length, eliminating the substrate's influence and improving the accuracy of soil moisture and density measurements.
Implementation Method 1
time domain reflection technology... measure the soil moisture content and density... electromagnetic wave propagation time along the waveguide... dielectric constant and conductivity of the medium
Implementation Method 2
using different volume ratio of ethanol and deionized water mixed solution to calculate a test target's medium weight coefficient and waveguide length... calculating a dielectric constant of the mixed solution
Implementation Method 3
using different concentrations of NaCl solution to calibrate waveguide geometric dimensioning of the non-invasive time domain reflection probes... calculating a conductivity of the NaCl solution
Data Source
AI summary
A non-invasive time domain reflection probe calibration method includes: using different volume ratio of ethanol and deionized water mixed solution to calculate a test target's medium weight coefficient and waveguide length of the non-invasive time domain reflection probes; using different concentrations of NaCl solutions to calibrate a waveguide geometric dimensioning of the non-invasive time domain reflection probes; preparing compacted soil samples with known different moisture contents and densities, and calibrating a correlation parameter of compacted soil samples' dielectric constant and conductivity with moisture content and density. The method not only determines the sensitivity of the test target medium of the non-invasive time domain reflection probes, but also obtains the waveguide length and geometric dimensioning of the probe, and realizes an accurate test of moisture content and density of the soil. The calibration method has an accurate calibration result, a wide application range, a convenient operation and a strong practicability.