Gas Sensor Thermistor Resistance Correction for Aging Drift
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Solution Overview
Problem
Existing gas sensors face issues with measurement errors due to aging of thermistors, which affect the accuracy of gas concentration calculations.
Innovation Solution
A gas sensor design that includes a detection circuit with two thermistors, heaters, and a control circuit to manage their connection and heating, allowing for separate resistance measurement and gas measurement operations, with corrections based on actual resistance values measured under controlled conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermistors are used in gas sensors to detect gas concentration, then gas detection capability is achieved, but measurement precision deteriorates due to aging-related temperature characteristic changes
Solution Approach 1:
The patent performs a resistance measurement operation before the gas measurement operation to obtain a resistance value of the first thermistor under controlled conditions (without heating). This preliminary measurement allows the system to detect aging-related changes in the thermistor's resistance characteristics before actual gas detection begins, enabling compensation or correction in subsequent gas concentration measurements.
Solution Approach 2:
The patent uses the resistance value measured during the resistance measurement operation to correct or compensate for the detection signal obtained during gas measurement. By feedback the actual resistance state of the thermistor (which may have changed due to aging) into the calculation system, the gas concentration measurement accuracy is maintained despite thermistor degradation over time.
2Measurement precision
If thermistors are heated to specific temperatures for gas measurement, then gas concentration detection is enabled, but device complexity increases due to need for separate resistance measurement and gas measurement operations
Solution Approach 1:
The patent divides the measurement process into two distinct operational modes: a resistance measurement operation where the first thermistor is measured without heating to obtain its resistance value, and a gas measurement operation where the thermistors are heated to detect gas concentration. This segmentation allows each operation to be optimized independently and enables the system to switch between modes based on measurement needs.
Solution Approach 2:
The detection circuit and control circuit are designed to perform multiple functions: they can conduct resistance measurement operations to characterize thermistor properties, gas measurement operations to detect gas concentration, and switch between these modes. The same hardware components serve both characterization and detection purposes, reducing the need for separate dedicated systems.
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
Reduces measurement errors by accurately measuring thermistor resistance values regardless of aging, ensuring precise gas concentration calculations.
Implementation Method 1
a first heater configured to heat the first thermistor; a second heater configured to heat the second thermistor
Implementation Method 2
a detection circuit including a first thermistor and a second thermistor; generate an output signal indicating a concentration of a gas to be measured based on a detection signal appearing at a connection point between the first and second thermistors
Data Source
AI summary
Disclosed herein is a gas sensor that includes: first and second thermistors; first and second heaters configured to heat the first and second thermistors, respectively; and a control circuit. The control circuit is configured to, in a gas measurement operation, generate an output signal based on a detection signal appearing at a connection point between the first and second thermistors by heating the first and second heaters. The control circuit is configured to, in a resistance measurement operation, measure a resistance value of the first thermistor with a series connection of the first and second thermistors disconnected. The control circuit is configured to correct a value of the output signal based on the resistance value of the first thermistor measured in the resistance measurement operation.