Micro-thermistor Gas Pressure Sensor Using Binary-wave Excitation
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Solution Overview
Problem
Conventional gas pressure sensors, such as Pirani gauges, face inaccuracies due to temperature fluctuations and fabrication errors, especially at low pressures, and struggle with integration into MEMS devices like bolometers and gyroscopes, requiring a solution for miniaturization and immunity to temperature fluctuations.
Innovation Solution
A micro-thermistor gas pressure sensor with a suspended platform device that uses binary-wave electrical excitation to measure ohmic responsivity, providing relative immunity to temperature fluctuations and compatibility with CMOS processes, allowing precise gas pressure measurement over a wide dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional Pirani gauges are used for wide dynamic range pressure measurement, then the sensor can cover a broad pressure range and remain relatively simple and inexpensive, but the sensor shows temperature sensitivity and cannot be easily integrated into MEMS devices
Solution Approach 1:
The sensor is divided into functionally independent components: a suspended platform structure for pressure sensing, a micro-thermistor for temperature measurement, and separate heating/reading circuits. This segmentation allows each component to be optimized independently and facilitates integration into MEMS devices while maintaining wide dynamic range capability
Solution Approach 2:
The suspended platform structure serves multiple functions: it acts as both the pressure sensing element and the mounting structure for the micro-thermistor. The micro-thermistor itself serves dual purposes as both a temperature sensor and a heating element, reducing the overall component count and simplifying integration
2Reliability
If conventional temperature compensation methods using bridge circuits are used, then temperature immunity is improved, but the structural complexity and readout circuit complexity increase, impeding MEMS integration
Solution Approach 1:
The micro-thermistor on the suspended platform serves itself as both the temperature sensor and the heating element. By measuring the self-heating effect and using it to infer pressure, the system eliminates the need for separate temperature compensation circuits and bridge readout electronics, achieving temperature immunity with minimal added complexity
Solution Approach 2:
The system changes the operating parameters by using the micro-thermistor's resistance change due to self-heating as the primary measurement signal. By operating in a regime where the thermistor's temperature coefficient is exploited, the system achieves temperature compensation through parameter measurement rather than through complex circuit compensation
3Ease of operation
If absolute voltage reading methods are used for pressure measurement, then the measurement method is simple, but fabrication errors cause inaccuracies that cannot be compensated
Solution Approach 1:
The system uses feedback by continuously monitoring the micro-thermistor resistance and adjusting the heating current to maintain a constant temperature difference between the platform and ambient. This feedback mechanism compensates for fabrication variations and environmental changes, improving measurement precision while maintaining operational simplicity
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 micro-thermistor sensor achieves precise gas pressure measurement with good immunity to temperature fluctuations and fabrication errors, enabling its integration into MEMS devices and compatibility with CMOS processes, thus addressing the challenges of miniaturization and dynamic range.
Implementation Method 1
a suspended electrical transducer that changes electrical resistance with a change of temperature
Implementation Method 2
the heat transferred from the micro-thermistor device to the environment is a function of the gas pressure
Implementation Method 3
The principle of gas pressure measurement consists in heating the micro-thermistor device with a binary-wave electrical excitation
Data Source
AI summary
An apparatus and method precisely measure gas pressure over a large dynamic range and with good immunity to temperature fluctuations, encompassing applications such as gas sensing, bolometer imaging and industrial process monitoring. The micro-thermistor gas pressure sensor assembly includes a suspended platform micro-thermistor sensor device exposed to the gas pressure of a given atmospheric environment, an electrical readout circuit connected to the suspended platform micro-thermistor sensor device, wherein the suspended platform micro-thermistor sensor device acts as a variable electrical resistance in the readout electrical circuit, a binary-wave voltage source connected to the suspended platform micro-thermistor sensor device, and an ohmmeter.