Gas Sensor Steady-State Current Prediction

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Solution Overview

Problem

Conventional gas sensors experience a delay in measurement accuracy due to the time required for the measurement pump current to settle to a steady-state value, which can lead to fluctuations in target component gas concentrations during switching periods, resulting in decreased measurement precision.

Innovation Solution

A gas sensor and measurement method that utilize a solid electrolyte with a preliminary oxygen concentration control unit to determine the steady-state value of the measurement pump current by analyzing the peak rate of change over time, allowing for earlier switching and reducing measurement time delays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the switching period is set longer than the time required for the measurement pump current to settle to a steady-state value, then the measurement stability is improved, but the measurement response time increases and measurement accuracy decreases due to gas concentration fluctuations

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidmeasurement response time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary action by predicting the steady-state value of the measurement pump current before the switching operation is completed. By analyzing the rate of change of the measurement pump current during the transient period and extrapolating to determine what the steady-state value would be, the system obtains measurement results without waiting for the actual settling process to complete, thus eliminating the time delay while maintaining measurement accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical waiting process (physically waiting for the measurement pump current to settle to steady-state) with a computational/mathematical approach. By calculating the rate of change of the measurement pump current and using this to predict the steady-state value through mathematical extrapolation, the system substitutes the time-consuming physical settling process with a faster computational method

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If the switching period is shortened to improve measurement response time, then the measurement speed increases, but measurement accuracy decreases due to fluctuations in target component gas concentration during the switching period

Engineering Contradiction:

Improvemeasurement speedVSAvoidmeasurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent performs preliminary determination of the steady-state value by analyzing the rate of change of the measurement pump current during the transient period. This allows the system to obtain accurate measurement results before the switching period completes, enabling shorter switching periods without sacrificing measurement accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent creates a computational model (a copy) of the settling process by analyzing the rate of change of the measurement pump current. This mathematical copy allows the system to predict the steady-state value without actually waiting for the physical settling process to complete, thus achieving fast measurements with high accuracy

Inventive Principle:

Principle #26Copying

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 enables faster determination of the steady-state value of the measurement pump current, shortening the switching period of the preliminary pump cell and preventing decreases in measurement accuracy caused by delays, thereby improving the precision of gas concentration measurements.

Implementation Method 1

a solid electrolyte that exhibits oxygen ion conductivity

Methodology Applied

Scientific EffectOxygen ion conductivity: Conduction (electrical)

Implementation Method 2

pump cells that include a preliminary pump electrode and a measurement electrode

Methodology Applied

Scientific EffectElectrochemical reaction: Electrolysis

Data Source

PatentUS11467122B2Gas sensor and gas concentration measurement method

Publication Date: 2022.10.11 NGK INSULATORS LTD

AI summary

In a gas sensor, which measures a measurement pump current Ip3 of a measurement chamber, while switching a preliminary pump cell of a preliminary chamber ON or OFF at a constant period, there are formed in communication with each other sequentially from a gas introduction port in the interior of a structural body made from a solid electrolyte, a preliminary chamber, an oxygen concentration adjustment chamber, and a measurement chamber. The gas sensor rapidly determines a steady-state value of a measurement pump current Ip3, based on a peak value of a rate of change over time dIp3/dt of the measurement pump current Ip3, thereby hastening an ON/OFF switching period of the preliminary pump cell.