MEMS Gas Sensor Humidity Adaptation via Periodic Heating

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Solution Overview

Problem

MEMS metal oxide semiconductor gas sensors are adversely affected by high humidity, leading to increased resistance and decreased gas response, which existing methods fail to adequately mitigate.

Innovation Solution

A gas detector with a MEMS gas sensor featuring a substrate, insulating film, and heater, where the drive circuit operates the heater with a predetermined pulse duration and includes a humidity detection mechanism to halt or elongate heating periods when high humidity is detected, thereby stabilizing the sensor's resistance and response.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the heater is operated continuously to maintain gas sensor performance, then gas detection reliability is improved, but power consumption increases and humidity influence worsens

Engineering Contradiction:

Improvegas detection reliabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The heater is operated periodically with a predetermined period and pulse duration rather than continuously. This periodic heating maintains the metal oxide semiconductor at operating temperature for gas detection while reducing overall power consumption and minimizing humidity-induced resistance changes that occur during continuous heating.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The heating operation is made dynamic by adjusting the period and pulse duration based on detected humidity levels. When high humidity is detected, the period is elongated or heating is halted temporarily, adapting the heating strategy to environmental conditions to prevent humidity influence while maintaining detection capability.

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If the heater operates with standard periodic pulses, then power consumption is reduced, but gas sensor response stability deteriorates under humid conditions

Engineering Contradiction:

Improvepower consumptionVSAvoidresistance stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

A humidity detection mechanism provides feedback to the drive circuit, which adjusts the heating operation accordingly. When high humidity is detected, the system responds by elongating the period or halting heating temporarily, creating a closed-loop control system that maintains resistance stability despite humidity variations while keeping power consumption low.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The heating parameters (period and pulse duration) are made dynamic and adaptive based on real-time humidity detection. This dynamic adjustment allows the system to maintain stable resistance characteristics under varying humidity conditions without requiring continuous high-power heating.

Inventive Principle:

Principle #15Dynamics

3Reliability

If humidity detection threshold is set strictly to prevent humidity influence, then sensor performance is protected, but detection capability in marginal conditions is reduced

Engineering Contradiction:

Improvesensor performance protectionVSAvoiddetection capability in marginal conditions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

Instead of using a fixed strict threshold, the system dynamically adjusts heating operation based on detected humidity levels. This dynamic approach allows the sensor to operate adaptively in marginal humidity conditions, maintaining detection capability while protecting against severe humidity influence through proportional response rather than binary threshold triggering.

Inventive Principle:

Principle #15Dynamics

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

This approach effectively prevents the negative impact of humid conditions on gas sensors by maintaining stable resistance and response, reducing the need for strict humidity thresholds and minimizing power consumption.

Implementation Method 1

a heater being provided on the insulating film; the drive circuit operates the heater with a predetermined period for a predetermined pulse duration in order to heat the metal oxide semiconductor

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

the resistance of the metal oxide semiconductor during the heating is used for gas detection. At the first stage during the heating, the resistance of the metal oxide semiconductor decreases rapidly

Methodology Applied

Scientific EffectGas sensing effect:

Implementation Method 3

a detection means for humidity for detecting humidity in an atmosphere

Methodology Applied

Scientific EffectHumidity detection:

Data Source

PatentUS11567021B2Gas detection device and gas detection method

Publication Date: 2023.01.31 FIGARO ENG INC

AI summary

A gas detector uses a MEMS gas sensor having: a substrate provided with a cavity and an insulating film over the cavity; a metal oxide semiconductor and a heater both provided on the insulating film. A drive circuit operates the heater with a predetermined period for a predetermined pulse duration in order to heat the metal oxide semiconductor. The drive circuit halts operation of the heater or elongates the period when a humidity sensor detects that the atmosphere is humid.