Capacitive Humidity Sensor Hysteresis Compensation

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Solution Overview

Problem

Capacitive humidity sensors face limitations in accuracy due to factors such as temperature, contamination, drift, aging, and hysteresis, which affect their calibration and measurement precision.

Innovation Solution

A capacitive humidity sensor design with hysteresis compensation using a trend-based process involving low-pass filters with different time constants to adjust sensor output, accounting for the sensor's history and rate of humidity change, thereby improving measurement accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a capacitive humidity sensor is used to measure humidity, then humidity measurement is achieved, but measurement precision deteriorates due to hysteresis effects

Engineering Contradiction:

Improvehumidity measurement accuracyVSAvoidsensor output consistency

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent implements a feedback mechanism by continuously monitoring the sensor output and comparing it with a reference value or previous measurements. The system adjusts the measurement based on the detected hysteresis pattern, using the sensor's own output history to compensate for inaccuracies. This closed-loop approach dynamically corrects hysteresis-induced errors without requiring external intervention.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the measurement parameters by introducing temperature compensation and using multiple measurement frequencies. By measuring at different frequencies and temperatures, the system captures the hysteresis behavior and uses this information to correct the primary humidity measurement. This multi-parameter approach transforms the hysteresis from a source of error into a correctable phenomenon.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If hysteresis compensation is implemented using trend-based process with low-pass filters, then measurement precision improves, but device complexity increases

Engineering Contradiction:

Improvehumidity reading accuracyVSAvoidsignal processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-calculating and storing the characteristics of the low-pass filters with different time constants. The compensation algorithm uses pre-established relationships between the filtered signals and hysteresis errors, eliminating the need for complex real-time calculations. This preparatory work simplifies the runtime processing while maintaining high measurement precision.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces intermediary low-pass filtered signals as mediators between the raw sensor output and the final compensated measurement. These intermediate signals with different time constants serve as bridges that capture various aspects of the hysteresis behavior, making the complex compensation task manageable through systematic combination of simpler processed signals.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 hysteresis-related inaccuracies by modifying sensor outputs based on humidity trends, leading to more accurate humidity readings by compensating for past environmental conditions and reducing estimation errors.

Implementation Method 1

capacitive based humidity sensors, the humidity has an effect on a dielectric constant of a polymer substance, metal oxide substance, or otherwise. The change in the dielectric constant is measured to determine the humidity.

Methodology Applied

Scientific EffectCapacitance: Capacitance