Dual-Unit Humidity Sensor Calibration for Drift Compensation

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Solution Overview

Problem

Capacitive and resistive humidity sensors using polymers as humidity sensitive materials suffer from humidity drift, particularly in high-temperature and high-humidity environments due to chemically adsorbed water vapor and polymer spatial expansion.

Innovation Solution

A drift-free humidity sensor design incorporating two humidity sensor units with different maximum humidity drifts, each with interdigital electrodes arranged in a staggered manner, and a calibration method that utilizes a differential sampling structure and processing units to compensate for drift by calculating and weighting measurement values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If polymer materials are used as humidity sensitive materials in capacitive and resistive sensors, then the sensors can be easily compatible with CMOS processes and have good linearity, but they will generate chemically adsorbed water vapor that is hard to desorb, resulting in humidity drift

Engineering Contradiction:

ImproveCMOS compatibilityVSAvoidhumidity drift

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The sensor is divided into two separate sensor units: a first sensor unit with a polymer humidity sensitive material and a second sensor unit with an inorganic humidity sensitive material. Each unit measures humidity independently, and their results are combined through weighting to compensate for the polymer's drift while maintaining CMOS compatibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the material parameter by introducing an inorganic humidity sensitive material with different physical and chemical properties compared to the polymer material. The inorganic material does not exhibit the same drift characteristics, and by combining measurements from both materials with different weighting factors, the system achieves drift compensation while maintaining manufacturing ease.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If polymer materials are used in high-temperature and high-humidity environments, then the sensors can operate in challenging conditions, but the long-chain spatial expansion of polymers will lead to more apparent humidity drift characteristics

Engineering Contradiction:

Improveenvironmental adaptabilityVSAvoidhumidity drift

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The inorganic humidity sensitive material acts as an intermediary reference that is not affected by temperature-induced polymer expansion. By comparing and combining measurements from both the polymer-based and inorganic-based sensor units, the system compensates for drift caused by environmental conditions while maintaining the ability to operate in high-temperature and high-humidity environments.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If a single humidity sensor unit is used, then the device structure is simple, but it cannot compensate for humidity drift effectively

Engineering Contradiction:

Improvesensor structureVSAvoiddrift compensation

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system uses feedback by continuously comparing measurements from both sensor units and dynamically adjusting the weighting factors based on environmental conditions. This feedback mechanism allows the system to compensate for drift in real-time while maintaining a relatively simple overall structure that can be integrated into existing CMOS processes.

Inventive Principle:

Principle #23Feedback

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 effectively mitigates humidity drift, ensuring accurate and drift-free humidity measurements across various environments with high applicability to different humidity sensitive materials and low implementation costs.

Implementation Method 1

due to the inherent characteristics of polymers, capacitive, resistive or pressure-sensitive type sensors using polymers as humidity sensitive materials will inevitably generate chemically adsorbed water vapor

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

the first measuring electrode and the second measuring electrode are capacitive electrodes

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

the first measuring electrode and the second measuring electrode are resistive electrodes

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Data Source

PatentUS12480902B2Drift-free humidity sensor and calibration method thereof

Publication Date: 2025.11.25 SHANGHAI SHENXILING MICROELECTRONICS TECH CO LTD

AI summary

A drift-free humidity sensor and a calibration method thereof are provided. The drift-free humidity sensor includes a first humidity sensor unit and a second humidity sensor unit. The first humidity sensor unit includes a first measuring electrode, and a first humidity sensitive material is covered onto the first measuring electrode. The second humidity sensor unit includes a second measuring electrode, and a second humidity sensitive material is covered onto the second measuring electrode. The first humidity sensor unit and the second humidity sensor unit have different maximum humidity drifts. The drift-free humidity sensor effectively solves the drift problem of ordinary capacitive or resistive humidity sensors.