Solid Rod Soil Probe With GPS Timing
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Solution Overview
Problem
Current soil moisture probes are fragile, difficult to install and remove, and suffer from accuracy issues due to mechanical shock susceptibility and interference from soil resistive elements like salt, which affects frequency measurements.
Innovation Solution
A solid rod moisture soil probe with sensors and circuitry on the outer surface, allowing for precise measurements close to the soil, powered by a wireless transmitter unit and battery pack, enabling GPS-derived precise timing for accurate frequency counting and featuring a slide hammer attachment for easy installation and removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If crystal or tuning-fork based oscillators are used to establish precise time period for frequency measurement, then measurement precision is improved, but reliability deteriorates due to susceptibility to mechanical shock and fragility
Solution Approach 1:
The patent changes the operating frequency parameter from nominal 100 MHz to at least 200 MHz. This higher frequency operation reduces the impact of resistive elements in the soil on measurement accuracy while maintaining reliable oscillator performance without requiring fragile crystal or tuning-fork devices
Solution Approach 2:
The patent replaces expensive, fragile crystal oscillators with simpler, more robust oscillator circuitry that can tolerate mechanical shock. While this may reduce theoretical precision, the system compensates through higher operating frequency and improved signal processing, achieving reliable field deployment without delicate components
2Ease of manufacture
If hollow cylindrical tube with large diameter is used to house circuitry, then ease of manufacture is improved, but ease of operation deteriorates due to difficulty in installation and removal
Solution Approach 1:
The patent divides the probe into modular segments: a hollow cylindrical tube for housing circuitry, separate sensor assemblies, and a threaded rod component. This segmentation allows each part to be manufactured independently and assembled field-ready, improving both manufacturing ease and field installation by enabling modular replacement and attachment of installation tools
Solution Approach 2:
The patent introduces a threaded rod as an intermediary component that connects the hollow tube to the sensor assemblies and provides a mechanical interface for installation tools. This intermediary element mediates between the manufacturing requirements of the tube and the operational requirements of easy installation/removal
3Reliability
If circuitry is positioned inside the hollow tube away from soil, then reliability is improved by protecting from damage, but measurement precision deteriorates due to reduced sensitivity to soil moisture
Solution Approach 1:
The patent implements a nested structure where sensor assemblies with capacitive elements are positioned within or adjacent to the hollow tube housing. The sensors are nested close to the soil interface while the main circuitry remains protected inside the tube, achieving both protection and sensitivity through this hierarchical arrangement
Solution Approach 2:
The patent extends the sensor elements beyond the tube housing in the radial dimension, allowing capacitive sensing surfaces to be positioned close to the soil while the electronic circuitry remains protected within the tube. This dimensional separation resolves the conflict between protection and sensitivity
4Ease of operation
If operating frequency is kept at nominal 100 MHz, then ease of operation is improved by reducing errors from resistive elements, but measurement precision deteriorates due to interference from salt and other soil elements
Solution Approach 1:
The patent changes the operating frequency parameter from nominal 100 MHz to at least 200 MHz. This higher frequency operation reduces the impact of resistive elements in the soil on measurement accuracy while maintaining reliable oscillator performance without requiring fragile crystal or tuning-fork devices
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
The solution provides a durable, easy-to-install, and accurate soil moisture measurement system with improved sensitivity and resistance to mechanical shock, minimizing errors from soil resistive elements.
Implementation Method 1
One common type of probe uses one or more sensors to measure the capacitance of the soil surrounding the sensor, with the measured capacitance converted—either at the probe or offboard—to a corresponding volumetric water content
Implementation Method 2
Because wet soil has a much higher dielectric constant than dry soil, a change in soil moisture results in a change in the soil dielectric and thus a change in combined capacitance
Implementation Method 3
When the combined 'capacitor' is used as part of an oscillator circuit, a change in soil moisture will result in a change in the frequency of the oscillator circuit and thus the soil moisture can be ascertained from the oscillator frequency
Data Source
AI summary
A moisture soil probe system includes a probe having a solid rod with a plurality of sensors attached around the outer circumference of the rod in close proximity to the soil being measured, covered by a waterproof coating. A wireless transmitter unit receives a precision GPS timing signal which is propagated to logic and control circuitry associated with each sensor for use in calculating a volumetric moisture content of the soil in proximity to the sensor. The calculated moisture content is transmitted back to the wireless control unit which further transmits the data to a central station.