Thermoelectric Moisture Sensor for Reduced Ion-Concentration Effects
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Solution Overview
Problem
Existing moisture sensors are susceptible to variations in measured values due to ion concentration, leading to unstable measurement results.
Innovation Solution
A moisture sensor utilizing a thermoelectric element to control temperature changes in the measurement object, with temperature measurement units on both heating and cooling surfaces, and an arithmetic unit to convert temperature change amounts into moisture information, minimizing the influence of ion concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance method or TDR method is used to measure moisture content, then moisture information can be obtained, but measurement stability deteriorates due to ion concentration influence
Solution Approach 1:
The invention changes the measurement parameter from electrical properties (capacitance, dielectric constant) to thermal properties (specific heat). By measuring the temperature change rate when a known amount of heat is applied, the system determines moisture content based on the specific heat capacity of the measurement object, which is less affected by ion concentration variations.
Solution Approach 2:
The invention replaces the electrical measurement system (capacitance method or TDR method) with a thermal measurement system. Instead of using electrical fields to probe moisture content, the system uses thermal energy input and measures the resulting temperature change, substituting electrical principles with thermal principles to eliminate ion concentration interference.
2Measurement precision
If temperature control unit operates to change measurement object temperature, then moisture information can be obtained through specific heat, but energy consumption increases
Solution Approach 1:
The temperature control unit operates periodically, applying heat to the measurement object in cycles. The heating element supplies heat for a predetermined time period, then stops, allowing the system to measure temperature change rate during the heating phase and reset during the cooling phase. This periodic operation reduces overall energy consumption compared to continuous heating.
Solution Approach 2:
The system applies heat for a predetermined, limited time period rather than continuously. The heating duration is optimized to provide sufficient temperature change for accurate measurement while avoiding excessive energy input. The heat application is partial in time, balancing measurement accuracy with energy efficiency.
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
Stable and accurate moisture measurements are achieved by utilizing specific heat properties, reducing the impact of ion concentration and enabling precise moisture content determination.
Implementation Method 1
a temperature control unit disposed in the measurement object and being able to change a temperature of the measurement object
Implementation Method 2
a temperature information acquisition unit acquiring temperature information indicating a temporal change of the temperature of the measurement object
Implementation Method 3
The temperature change amount is based on specific heat of the measurement object. The specific heat, which is a physical quantity, is less susceptible to a disturbance.
Data Source
AI summary
The soil moisture sensor includes a thermoelectric element disposed in the soil, a first temperature information acquisition unit acquiring a first temperature information that indicates a temporal change in temperature of the soil due to an operation of the thermoelectric element, a second temperature information acquisition unit acquiring a second temperature information that indicates a temporal change in temperature of the soil due to the operation of the thermoelectric element, and an arithmetic device obtaining moisture information on the basis of the temperature information. The arithmetic device includes a gradient information acquisition unit acquiring a temperature change amount per unit time by utilizing the first temperature information and the second temperature information, and a conversion unit converting the temperature change amount into the moisture content by utilizing conversion information indicating a relationship between the temperature change amount and the moisture content.