Thermal Gas Sensor for Binary Mixture Concentration at Variable Pressure
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Solution Overview
Problem
Thermal type gas sensors are unable to determine the concentration of a gas in a binary mixture at variable pressure, as pressure significantly influences thermal conductivity, making it impossible to accurately measure gas concentration solely based on membrane temperature measurements.
Innovation Solution
A thermal gas sensor that measures both static and dynamic parameters of the gas mixture, using a specific frequency for the current source to heat and measure the membrane, allowing for the calculation of gas concentration and pressure through mathematical functions, eliminating the need for an additional pressure sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermal gas sensor measures only membrane temperature to determine gas concentration, then the measurement is simple and low-cost, but it becomes impossible to accurately determine concentration at variable pressure since pressure strongly influences thermal conductivity
Solution Approach 1:
The patent applies parameter changes by measuring multiple parameters (membrane temperature and transient response characteristics) instead of a single parameter. By analyzing the transient response of the membrane temperature during pressure changes, the sensor can distinguish between temperature changes caused by concentration variations and those caused by pressure variations, enabling accurate concentration measurement at variable pressure without adding a separate pressure sensor.
Solution Approach 2:
The patent utilizes the continuous monitoring of membrane temperature during normal sensor operation. Instead of requiring separate pressure measurements, the system continuously analyzes the transient temperature response as pressure changes occur, extracting concentration information from the dynamic behavior of the membrane temperature curve. This approach maintains measurement capability throughout pressure variations without interrupting the sensing process.
2Measurement precision
If a pressure sensor is added to enable concentration measurement at variable pressure, then measurement accuracy is improved, but the cost and complexity of the detection system substantially increase
Solution Approach 1:
The patent makes the thermal gas sensor multi-functional by enabling it to simultaneously measure gas concentration and detect pressure changes through its transient response characteristics. The same membrane and heating elements that measure temperature also provide pressure information through their dynamic response to pressure changes. This eliminates the need for a separate pressure sensor, reducing system cost and complexity while maintaining measurement accuracy at variable pressure.
Solution Approach 2:
The sensor system performs self-diagnosis and self-measurement by analyzing its own transient temperature response to pressure changes. The membrane and heating elements inherently respond to both concentration and pressure changes, and the evaluation unit extracts both types of information from the same temperature signal. This self-service approach allows the sensor to determine concentration at variable pressure using only its existing components, avoiding additional hardware costs.
3Speed
If the membrane has low thermal inertia for responsive measurement, then the sensor responds quickly to gas composition changes, but it becomes more sensitive to pressure fluctuations, making concentration determination impossible without pressure compensation
Solution Approach 1:
The patent applies dynamics by analyzing the transient (dynamic) response of the membrane temperature rather than relying solely on steady-state measurements. The low thermal inertia membrane quickly responds to both concentration and pressure changes, creating characteristic transient temperature curves. By evaluating the dynamic behavior of these curves during pressure transitions, the system can separate concentration effects from pressure effects, maintaining both fast response and accurate concentration measurement at variable pressure.
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 determination of gas concentration and pressure in binary mixtures, even at varying pressures, reducing the overall cost and complexity of detection systems.
Implementation Method 1
When the latter is heated by the heating means, its temperature settles at a stable value, which depends on the thermal conductivity of the gaseous mixture or of the surrounding gas
Implementation Method 2
The metal used for the means of measuring the temperature has a variable resistance as a function of the temperature, so that the measurement of the voltage at its terminals makes it possible to determine the temperature of the membrane
Implementation Method 3
The thermal conductivity λ of a gas is its capacity to transport heat, under the effect of a temperature gradient. It is an intrinsic quantity of a gas at a given pressure and temperature
Data Source
Figure 1~3
AI summary
The sensor has a measurement cell (1) intended to be located in a two-component mixture including a membrane (12) of low thermal inertia on which heating units i.e. heating devices (13), for the membrane are arranged. A source of alternating current of frequency is intended to supply the heating units and an electronic circuit, where the frequency is selected to calculate value of concentration of the gas and the pressure of mixture from parameters with the assistance of established mathematical function and characteristic coefficients of the sensor. An independent claim is also included for a method for determining concentration of gas in a two-component mixture at variable pressure.