Micromachined Thermal Field Pressure Sensor Design
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Solution Overview
Problem
Current pressure sensors face limitations in achieving high precision, large dynamic range, and cost-effectiveness, particularly in measuring absolute, gauge, and differential pressures, with issues such as low sensitivity at low pressures, nonlinearity, and susceptibility to contaminants, which hinders their integration with other sensing devices in miniaturized formats.
Innovation Solution
A micromachined thermal field pressure sensor (TFPS) utilizing a diaphragm structure with thermistors that register thermal field changes due to membrane deflection, enabling sensitive pressure measurements across a wide range, compatible with thermal flow sensors and capable of operating in the presence of contaminants, with a manufacturing process similar to integrated circuitry to ensure low cost and high volume production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If piezo resistive pressure sensors are used, then cost effectiveness is improved, but measurement precision deteriorates due to small dynamic range and large errors at low end detection
Solution Approach 1:
The patent replaces the mechanical piezo resistive sensing system with a thermal field-based sensing system. Instead of using strain gauges that measure mechanical deformation, the invention uses thermistors to detect thermal field changes caused by membrane deflection. This substitution enables high precision measurements while maintaining compatibility with cost-effective micromachining processes.
Solution Approach 2:
The patent changes the sensing parameter from mechanical resistance (piezo resistive) to thermal conductivity (thermal field). By measuring thermal field changes rather than mechanical strain, the system achieves extended dynamic range and improved low-end detection accuracy while maintaining manufacturing simplicity through standard micromachining techniques.
2Reliability
If capacitive pressure sensors are used, then temperature performance is improved, but device size increases and burst pressure decreases due to larger membrane size requirements
Solution Approach 1:
The patent replaces the capacitive sensing system with a thermal field sensing system. Instead of measuring capacitance changes between membrane and reference plate, the invention uses thermistors to detect thermal field variations. This substitution maintains good temperature performance while enabling significant miniaturization of the membrane and overall device structure.
Solution Approach 2:
The patent transitions from measuring electrical field changes (capacitive) to measuring thermal field changes. This dimensional shift in the sensing mechanism allows for reduced membrane size while maintaining sensitivity, as thermal conduction paths can be optimized independently of membrane area, enabling smaller device footprint without sacrificing temperature performance.
3Measurement precision
If dual thermal microbridge based absolute gas pressure sensor is used, then absolute pressure measurement capability is improved, but signal processing complexity increases and nonlinearity appears at low pressure end
Solution Approach 1:
The patent extracts the sensing function from complex dual microbridge structures with multiple heaters and thermistors, simplifying to a single membrane with strategically placed thermistors. By removing unnecessary heating elements and using the membrane itself as the thermal field source, the system achieves absolute pressure measurement capability with significantly reduced signal processing complexity and improved linearity across the pressure range.
Solution Approach 2:
The patent implements self-service by using the pressure membrane itself as the thermal field source rather than requiring external heaters. The membrane's thermal conduction properties directly reflect pressure conditions, eliminating the need for complex heating circuits and polynomial fitting calculations, thereby reducing signal processing complexity while maintaining measurement accuracy.
4Adaptability or versatility
If pressure sensors are miniaturized for integration with other sensing devices, then adaptability is improved, but sensitivity at low pressures deteriorates
Solution Approach 1:
The patent replaces mechanical strain gauge systems with thermal field sensing, enabling miniaturization without sacrificing low-pressure sensitivity. The thermal conduction-based measurement mechanism scales effectively to smaller dimensions, allowing the sensor to maintain high sensitivity in compact formats suitable for integration with other sensing devices in miniaturized 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
The TFPS achieves high sensitivity and large dynamic range pressure measurements with linear output, is resistant to contaminants, and can be easily integrated with flow sensors, suitable for various applications, including those requiring miniaturized formats, while maintaining stability and reliability.
Implementation Method 1
A micro-heater on the said membrane creates a stable thermal field
Implementation Method 2
at least one pair of the thermistors symmetrically or asymmetrically placed at the both side against the micro-heater... the thermistors shall register such changes
Data Source
AI summary
The design and manufacture method of a pressure sensor utilizing thermal field sensing with a thermal isolated membrane of a diaphragm structure is disclosed in the present invention. This device is made with silicon micromachining (a.k.a. MEMS, Micro Electro Mechanical Systems) process for applications of pressure measurement with large dynamic range, high accuracy and high stability during temperature variation. This device is applicable for all types of pressure metrology. The said thermal field pressure sensing device operates with thermistors on a membrane of the diaphragm structure made of silicon nitride with a heat isolation cavity underneath or a single side thermal isolated silicon nitride membrane with a reference cavity. This device can be seamlessly integrated with a thermal flow sensor with the same process.