Gas Sensor Reference Element for Accuracy
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Solution Overview
Problem
Existing gas sensor systems face challenges in maintaining accuracy due to factors like temperature, voltage, drift, frequency, and noise, and are often hindered by the high cost and unavailability of precision components.
Innovation Solution
A gas sensor design incorporating a reference element of the same type and geometry as the gas-sensing element on the same substrate, with electronic circuitry that measures the voltage difference between them, which is proportional to gas concentration and insensitive to temperature, voltage, drift, and noise variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If precision reference components are used to improve measurement accuracy, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent creates a reference element that is a copy of the sensing element in terms of geometry, material composition, and electrical properties, but differs in gas sensitivity. This copying approach allows the reference element to track environmental effects (temperature, voltage drift, noise) without requiring expensive precision components, as the reference and sensing elements naturally experience identical conditions due to their congruent construction
Solution Approach 2:
The patent segments the sensor system into two functionally distinct but structurally identical elements: a gas-sensitive element and a reference element. This segmentation allows independent optimization of each element's function while maintaining manufacturing simplicity through standardized fabrication processes for both elements
2Measurement precision
If tighter tolerances on electronic components are used to reduce temperature and voltage effects, then measurement precision is improved, but device complexity increases
Solution Approach 1:
By creating a reference element that is a structural copy of the sensing element, the system eliminates the need for complex compensation circuits. The reference element passively tracks environmental variations, and the simple voltage difference measurement automatically compensates for temperature and voltage effects without requiring complex electronics or tight component tolerances
3Measurement precision
If a reference element is integrated on the same substrate, then measurement precision is improved by canceling environmental effects, but device complexity increases
Solution Approach 1:
The patent merges the reference element and sensing element onto the same substrate, fabricating both elements using identical processes and materials. This integration ensures both elements experience identical environmental conditions (temperature, voltage, mechanical stress, noise), allowing environmental effects to cancel out in the voltage difference measurement while simplifying the overall device structure through monolithic fabrication
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 approach provides higher accuracy and lower costs by using lower precision components, effectively canceling out noise and temperature-related errors, and has been shown to detect hydrogen concentrations below 10 ppm with stability across various conditions.
Implementation Method 1
Each of the gas-sensing element and the reference element can be a metal-gated metal-oxide semiconductor (MOS) solid-state device. The metal gate of the gas-sensing MOS device preferably comprises a metal selected from the group consisting of palladium and a palladium alloy.
Implementation Method 2
The gas detection circuitry actuates both the gas-sensitive and reference elements and measures the voltage difference between them. The voltage difference is proportional to the gas concentration and is essentially undominated by changes in temperature, voltage, drift, frequency, noise and/or other similar factors.
Implementation Method 3
a thermally conductive, electrically insulative substrate
Data Source
AI summary
A system for sensing a gas stream constituent comprises: (a) a thermally conductive, electrically insulative substrate, (b) a gas-sensing element mounted on the substrate and capable of sensing the constituent, (c) a reference element mounted on the substrate having electrical properties congruent with the gas-sensing element and being insensitive to the constituent, (d) an electronic circuit interconnecting the gas-sensing element and the reference element. The circuit is capable of actuating both of the elements and measuring the voltage difference between the elements. The voltage difference is proportional to the concentration of the constituent in the gas stream.