Differently Sized Thermal Sensor Cells for Gas Property Compensation
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Solution Overview
Problem
Conventional thermal flow sensors are influenced by gas properties such as density, heat conductivity, and specific heat capacity, leading to inaccurate flow rate measurements due to changes in temperature and pressure, requiring additional sensors for calibration or compensation.
Innovation Solution
A sensor arrangement with two differently dimensioned sensor cells, each sensitive to either heat conductivity or volume heat capacity, allowing independent determination of these properties through oscillation behavior analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal flow sensors are used to measure flow rate, then flow measurement is achieved, but the output signal is influenced by gas properties (density, heat conductivity, specific heat capacity) leading to measurement inaccuracy
Solution Approach 1:
The sensor system is segmented into multiple independent sensor cells (first sensor cell, second sensor cell, third sensor cell) each measuring different gas properties. This segmentation allows separate measurement of heat conductivity, volume heat capacity, density, and temperature, which are then combined through evaluation to compensate for mutual influences and achieve accurate flow rate measurement.
Solution Approach 2:
The invention changes the measurement parameters from direct flow rate measurement to measuring fundamental gas properties (heat conductivity, volume heat capacity, density, temperature) separately. By measuring these underlying parameters and using them for compensation, the system overcomes the limitation that thermal flow sensor output is directly influenced by gas property variations.
2Measurement precision
If additional sensors are added to compensate for gas property influences, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
Multiple sensor cells measuring different gas properties are merged into a single integrated sensor arrangement with unified evaluation. The first, second, and third sensor cells are combined on one device, sharing common structures and evaluation logic, which reduces overall system complexity compared to using separate independent sensors while maintaining the ability to compensate for all gas property influences.
Solution Approach 2:
The sensor arrangement is designed with multi-functionality where the same basic sensor cell structure can measure different gas properties depending on configuration. The evaluation unit universally processes signals from multiple sensor cells to determine various gas properties and perform compensation, making the system adaptable without requiring separate specialized sensors for each measurement.
3Measurement precision
If sensors are located in direct proximity to the flow sensor, then signal compensation precision is improved, but integration difficulty increases
Solution Approach 1:
The sensor cells are nested within a compact integrated structure where multiple measurement chambers are arranged in close proximity. The first, second, and third sensor cells are positioned adjacent to each other and to the flow sensor, allowing direct measurement of the same gas flow while minimizing spatial separation. This nested arrangement achieves high compensation precision while maintaining manufacturability through integrated device 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
Enables precise determination of heat conductivity and volume heat capacity without additional sensors, improving the accuracy of flow and pressure measurements in thermal sensors.
Implementation Method 1
a first sensor cell which can be excited thermally by means of a first heater
Implementation Method 2
configured to form a respective oscillation behavior, in particular oscillation behavior of the respective first or second heater, in dependence on a gas property of a gas surrounding the first and second sensor cell
Implementation Method 3
the heat conductivity is determined based on the oscillation behavior of the first sensor cell
Implementation Method 4
the volume heat capacity is determined based on the oscillation behavior of the second sensor cell
Data Source
AI summary
A sensor arrangement having: a first sensor cell which can be excited thermally by means of a heater; a second sensor cell which can be excited thermally by means of a heater; and an evaluation; wherein the first and second sensor cells are sensor cells of the same kind and are dimensioned and/or configured differently, and are configured to form a respective oscillation behavior in dependence on a gas property of a gas surrounding the sensor cells, in particular heat conductivity, volume heat capacity, temperature and/or pressure, and the evaluation is configured to evaluate the oscillation behavior of the first and second sensor cells together in order to determine the heat conductivity and volume heat capacity, heat conductivity being determined based on the oscillation behavior of the first sensor cell and volume heat capacity being determined based on the oscillation behavior of the second sensor cell.