FET Gas Sensor Phase Feedback for High Temperature Stability
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Solution Overview
Problem
Field effect type (FET) gas sensors face challenges in maintaining reliable gas concentration detection under high temperature environments due to non-linear current-voltage characteristics at contact portions, leading to instability and increased data processing costs, and existing methods for detecting gas concentrations are not optimal for such conditions.
Innovation Solution
A gas sensor design incorporating a capacitance element with an inductor forming a resonant circuit, a phase detection circuit to detect phase differences between standard and resonant frequencies, and a feedback unit to adjust voltage and maintain constant capacitance, thereby stabilizing gas concentration detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If FET gas sensor is used for high temperature operation, then the sensor can operate without additional cooling devices and can remove soot stains, but the contact portions exhibit non-linear current-voltage characteristics leading to detection instability
Solution Approach 1:
The patent implements a feedback mechanism where the measured capacitance value is continuously compared against a reference value, and the gate-source voltage is adjusted based on the difference to maintain stable detection. This feedback loop compensates for the non-linear characteristics at high temperatures, ensuring reliable operation without additional cooling devices.
Solution Approach 2:
The patent changes the operating parameters by introducing capacitance measurement and dynamic voltage adjustment. Instead of operating with fixed voltage, the system measures capacitance and adjusts the gate-source voltage accordingly, transforming the detection method to accommodate high-temperature non-linear characteristics.
2Device complexity
If conventional detection method is used, then the sensor structure is simple, but the detection accuracy decreases under high temperature conditions
Solution Approach 1:
The patent introduces capacitance measurement as an intermediary parameter between the gas detection function and the output signal. By measuring the capacitance of the gate insulating film, which changes with gate-source voltage, the system obtains accurate gas concentration data under high-temperature conditions without significantly complicating the sensor structure.
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 solution enables stable and reliable gas concentration detection even under high temperature conditions, minimizing the influence of accumulated charges and maintaining high stability, thus improving the reliability of gas sensors.
Implementation Method 1
an inductor connected to the element unit and forming a resonant circuit in cooperation with the capacitance of the element unit; a phase detection circuit detecting a phase difference between a standard frequency and a resonant frequency of the resonant circuit
Data Source
AI summary
A gas sensor capable of stably detecting a gas concentration with a high reliability even under a high temperature environment is provided. The gas sensor includes an element unit having a capacitance value changing in accordance with a gas concentration, an inductor forming a resonant circuit in cooperation with the element unit, a phase detection circuit detecting a phase difference between a standard frequency and a resonant frequency of the resonant circuit, and a feedback unit supplying, to the element unit, a voltage changing in accordance with the phase difference detected by the phase detection circuit. The capacitance value of the element unit is controlled by the voltage from the feedback unit so as to reduce the phase difference between the resonant frequency and the standard frequency, and a gas concentration detection output is output based on the phase difference.