Thermal Gas Sensor Structures for Disturbance-Gas Compensation
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Solution Overview
Problem
Thermal sensor devices face challenges in accurately determining the concentration of a target gas due to cross-sensitivities to disturbance gases, temperature, and pressure changes, which affect the accuracy of measurements.
Innovation Solution
A thermal sensor device with first and second measurement structures having different heat dissipation capabilities, utilizing a processing circuitry to derive an output signal based on a weighted difference of temperature signals, reducing sensitivity to disturbance gas and pressure changes by optimizing the geometry and weights of the sensor components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single thermal sensor is used to measure target gas concentration, then the measurement is simple and cost-effective, but the accuracy is compromised due to cross-sensitivity to disturbance gases
Solution Approach 1:
The single thermal sensor is segmented into two measurement structures with different heat dissipation capabilities (different thermal conductances to substrate). This segmentation allows the system to differentiate between target gas and disturbance gas effects by comparing responses from the two structures, thereby improving measurement accuracy while maintaining cost-effectiveness.
Solution Approach 2:
The two measurement structures are designed with different local thermal properties (different thermal conductances to substrate). This local quality difference enables selective sensitivity to different gas components, allowing the system to compensate for disturbance gas cross-sensitivity while maintaining simplicity.
2Measurement precision
If additional sensors (humidity sensor, temperature sensor, pressure sensor) are used to compensate for cross-sensitivities, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The thermal sensor device performs multiple functions using a single sensor type: it measures target gas concentration, disturbance gas concentration, temperature, and pressure simultaneously. The two measurement structures with different thermal conductances enable this multi-functionality, eliminating the need for separate humidity, temperature, and pressure sensors while maintaining high measurement accuracy.
Solution Approach 2:
The system changes the thermal conductivity parameter of the measurement structures by designing them with different thermal conductances to the substrate. This parameter variation enables the same sensor type to respond differently to various gas components and environmental conditions, providing intrinsic compensation for cross-sensitivities without additional sensors.
3Measurement precision
If sequential measurements at different heating powers or frequencies are used to compensate for humidity effects, then measurement accuracy is improved, but measurement time and productivity decrease
Solution Approach 1:
The system performs continuous simultaneous measurements using two measurement structures operating in parallel. Both structures measure different aspects of the gas composition concurrently, eliminating the need for sequential measurements at different heating powers or frequencies. This maintains high measurement accuracy while maximizing measurement speed and productivity.
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 device achieves reduced sensitivity to concentration changes of disturbance gases and pressure, enhancing the accuracy and reliability of target gas concentration measurements.
Implementation Method 1
Heat transfer between the heater and the temperature sensors is influenced by heat transfer through the fluid
Implementation Method 2
a first temperature sensor for determining a first temperature signal, the first temperature signal being indicative of a temperature of the first measurement structure
Implementation Method 3
at least one heater element operable to cause heat transfer to the first and second measurement structures
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A thermal sensor device serves for determining a concentration of a target gas in a gas sample that further comprises a disturbance gas. The thermal sensor device comprises first and second measurement structures (1, 2) comprising first and second temperature sensors (TS1, TS2) and a heater element (31) operable to cause heat transfer to the measurement structures through the gas sample. Processing circuitry provides heating power (P3) to the heater element and derives an output signal (S) based on a response of the temperature sensors to the heating power, the output signal being indicative of a concentration of the target gas in the gas sample. The first and second measurement structures have different heat dissipation capabilities, and the processing circuitry derives the output signal from a weighted difference of temperature signals from the first and second temperature sensors. Thereby, a a cross-sensitivity of the output signal to a concentration change of the disturbance gas may be reduced or eliminated.