Gas Sensor Impedance Correction for Humidity Interference
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Solution Overview
Problem
Conventional metal oxide semiconductor (MOS) gas sensors measure only DC resistance and are affected by environmental conditions like relative humidity, leading to unreliable gas detection, especially for small gas concentrations, and require separate humidity sensors increasing cost and complexity.
Innovation Solution
A system and method that incorporates a gas sensor with an interferent-compensating sensing element in a single electrical circuit, using dielectric excitation to measure impedance responses at various frequencies, allowing for the determination of environmental conditions and correction of gas sensor responses to accurately identify and quantify gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MOS sensors measure only DC resistance, then the sensor structure is simple, but the measurement precision is poor and reliability is low under varying environmental conditions
Solution Approach 1:
The patent applies periodic action by using AC excitation signals at multiple frequencies to probe the sensor circuit. The impedance detector measures responses at different frequencies, enabling separation of gas-related impedance changes from humidity-related changes through frequency-domain analysis. This periodic excitation approach transforms the single DC measurement into multiple AC measurements, improving measurement precision while managing device complexity through systematic signal processing.
Solution Approach 2:
The patent implements parameter changes by varying the excitation frequency across multiple values. By measuring impedance responses at different frequencies, the system can distinguish between different physical phenomena affecting the sensor (gas adsorption versus humidity effects). This multi-frequency parameter variation enables more accurate gas detection by allowing mathematical separation of interfering effects, thereby improving measurement precision without requiring additional physical sensors.
2Reliability
If separate humidity sensors are added to correct environmental effects, then the measurement precision improves, but the device complexity and power consumption increase
Solution Approach 1:
The patent applies universality by making the impedance detector perform multiple functions: it simultaneously measures both gas concentration and humidity effects through multi-frequency AC impedance measurements. The same detector circuit that would normally only measure resistance now also characterizes capacitive effects related to humidity. This multi-functionality eliminates the need for separate humidity sensors, maintaining reliability while reducing device complexity and power consumption.
Solution Approach 2:
The sensor circuit performs self-service by using its own impedance characteristics at different frequencies to automatically compensate for humidity effects. The system extracts humidity information from the capacitive component of the impedance and uses this information to correct the gas measurement, without requiring external humidity sensors or additional correction hardware. This self-service approach improves reliability while minimizing added complexity.
3Measurement precision
If AC excitation at multiple frequencies is used, then the measurement precision and reliability improve by enabling interferent correction, but the use of energy increases
Solution Approach 1:
The patent uses periodic AC excitation at multiple frequencies to achieve precise gas measurements and humidity compensation. By systematically varying the excitation frequency and measuring impedance responses, the system extracts both gas concentration and humidity information from the same energy input. This periodic measurement approach improves measurement precision while managing power consumption through efficient use of the excitation signal across multiple measurement dimensions.
Solution Approach 2:
The system performs self-service by extracting multiple pieces of information (gas concentration and humidity) from a single multi-frequency impedance measurement. Rather than requiring separate sensors that would each consume power, the system uses the impedance detector to simultaneously gather both types of data from the same energy input, thereby improving measurement precision without proportionally increasing power consumption.
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 reliable gas detection across a wider range of environmental conditions by correcting for interferent conditions, reducing the number of components and power consumption, and providing accurate identification and quantification of gases.
Implementation Method 1
The impedance detector is configured to provide dielectric excitation of the gas sensing element and the interferent-compensating sensing element at a set of frequencies
Implementation Method 2
measure impedance responses of the sensing circuit to the dielectric excitation at the set of frequencies
Data Source
AI summary
A system and a method for gas sensing while correcting for an interferent condition around a gas sensor. The gas sensor provides dielectric excitation of a gas sensing element and an interferent-compensating sensing element arranged as a single electrical circuit at a set of frequencies, measures impedance responses of the gas sensing element and the interferent-compensating sensing element to the dielectric excitation at the set of frequencies, determines, based on the impedance responses of the gas sensing element and the interferent-compensating sensing element to the dielectric excitation the identities, the respective concentrations, or a combination thereof, of at least one analyte gas of the monitored environment, corrected for one or more sensed interferent conditions of the ambient environment.