Resonant Gas Sensor Humidity Correction via Capacitance
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Solution Overview
Problem
Existing gas sensors lack specificity and are affected by humidity, leading to interference from water molecules, which complicates the detection of target gases due to their sensitivity to moderate humidity changes and the omnipresence of water.
Innovation Solution
A resonant sensor device with a capacitor formed by electrodes and a sensing material, capable of distinguishing between analyte and water molecules by measuring both the mechanical response and capacitance changes, allowing for accurate detection of target gases while accounting for humidity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resonant sensor is used to detect analyte, then sensitivity to analyte molecules is improved, but sensitivity to humidity changes worsens
Solution Approach 1:
The sensor system is segmented into two independent sensing channels: a resonant sensor for detecting analyte mass and a capacitor for detecting water content. Each sensor type targets a specific aspect (mass change vs. dielectric change), allowing the system to separate analyte detection from humidity interference by dividing the measurement functions.
Solution Approach 2:
The capacitor acts as an intermediary sensor that specifically measures water content through dielectric constant changes. This intermediary measurement of humidity allows the system to compensate for water interference in the resonant sensor readings, mediating between the analyte detection and humidity effects.
2Object-affected harmful factors
If filter or membrane is added to block water access, then humidity interference is reduced, but cost and device complexity increase
Solution Approach 1:
The patent replaces mechanical filtration approaches with an electrical measurement approach. Instead of using physical filters or membranes to block water, the system uses a capacitor to electrically sense water content through dielectric constant changes, substituting a mechanical solution with an electrical field-based solution.
Solution Approach 2:
The capacitor serves as an intermediary that indirectly measures water content without requiring physical separation or blocking mechanisms. This intermediary sensing approach avoids the complexity of filters while still achieving humidity compensation.
3Measurement precision
If second sensing material is added to monitor water adsorption, then humidity correction is enabled, but errors between different materials increase measurement uncertainty
Solution Approach 1:
The patent changes the measurement parameter from mass-based (resonant frequency) to dielectric-based (capacitance). By using the capacitor's dielectric constant measurement, the system directly measures water content without relying on comparative adsorption between different sensing materials, eliminating the reliability issues associated with material variability.
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
Enables precise detection of analytes like carbon dioxide and methane by differentiating between water and target gas molecules, reducing errors and maintaining sensitivity without increasing cost, size, or complexity.
Implementation Method 1
at least one resonant sensor having an oscillating portion... a processor programmed to determine an analyte value in dependence upon measurements of both a response of the oscillating portion (e.g., a frequency shift or a change in resonance frequency)
Implementation Method 2
measure... a capacitance of the capacitor... The capacitor is formed by at least two electrodes and a sensing material positioned between the electrodes
Implementation Method 3
The capacitor is formed by at least two electrodes and a sensing material positioned between the electrodes... measure a capacitance of the capacitor
Implementation Method 4
When measuring an analyte in ambient environmental conditions, the sensor indicates not only a mass change due to the target gas, but also due to the additional adsorption of water molecules in the sensing material
Data Source
AI summary
A device and method are provided for detecting analyte with correction for the effects of humidity. The device comprises a resonant sensor having an oscillating portion. A capacitor is positioned on the oscillating portion. The capacitor is formed by at least two electrodes and a sensing material positioned between the electrodes. A readout circuit is arranged to measure a response of the oscillating portion (e.g., frequency shift or change in resonance frequency, stiffness or strain) and a capacitance of the capacitor when substances are adsorbed or absorbed in the sensing material. This combination of measurements enables the device to distinguish between various types of adsorbed or absorbed molecules, especially distinguishing between an analyte of interest and water molecules that might interfere with the detection of the analyte. A processor determines an analyte value indicative of the presence, amount or concentration of the analyte in dependence upon measurements of both the response of the oscillating portion and the capacitance to account for the effects of water in the sensing material.