Gas Sensor Calibration via Heater Current Noise

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Solution Overview

Problem

Existing gas concentration detecting apparatuses face challenges in eliminating noise components from the output signal of gas sensors, particularly temperature control noise components that affect detection accuracy, despite using PWM control for the heater.

Innovation Solution

A gas concentration detecting apparatus with a sensor control apparatus that includes a change rate calculation unit to determine the change rate of the heater current when the sensor cell is at a target temperature, allowing the calibration outputting unit to calibrate the sensor output and eliminate temperature control noise components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If PWM control is used to control the heater, then the responsivity to load variation is improved, but temperature control noise components are generated that affect detection accuracy

Engineering Contradiction:

Improveresponsivity to load variationVSAvoiddetection accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent converts the harmful temperature control noise generated by PWM heater control into a useful calibration signal. By detecting the noise component in the sensor output and using it to calculate calibration values, the system transforms the detrimental effect into a beneficial correction mechanism that actually improves measurement precision.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent implements a feedback mechanism where the sensor output is continuously monitored to detect temperature control noise components. The detected noise is fed back to calculate calibration values that are then applied to correct the sensor output, creating a closed-loop system that actively compensates for the noise generated by PWM control.

Inventive Principle:

Principle #23Feedback

2Stability of the object's composition

If the heater is energized to maintain sensor cell temperature, then the sensor operation is stabilized, but noise components are generated in the sensor output

Engineering Contradiction:

Improvesensor cell temperature stabilityVSAvoidtemperature control noise components

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful temperature control noise generated by heater energization into a useful calibration signal. By detecting the noise component in the sensor output and using it to calculate calibration values, the system transforms the detrimental effect into a beneficial correction mechanism that actually improves measurement precision.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces a calibration value as an intermediary element that mediates between the heater control system and the sensor output. This calibration value acts as a translator that converts the temperature control noise into a corrective factor, allowing the system to maintain temperature stability while eliminating the harmful noise effects.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Use of energy by moving object

If PWM control is applied to the heater, then energy efficiency is improved, but detection accuracy deteriorates due to noise components

Engineering Contradiction:

Improveheater energy efficiencyVSAvoidsensor output accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the parameter being controlled from direct temperature control to noise-based calibration. Instead of trying to eliminate the PWM noise directly, the system changes approach by using the noise itself as a parameter to calculate calibration values, thereby maintaining energy efficiency while improving detection accuracy.

Inventive Principle:

Principle #35Parameter changes

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

Enhances the detection accuracy of gas concentration by effectively eliminating noise components, improving the reliability of the sensor output.

Implementation Method 1

a heater generating heat when being energized to heat the sensor cell

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS20240003842A1Gas concentration detecting apparatus

Publication Date: 2024.01.04 DENSO CORP

AI summary

A sensor control apparatus of a gas concentration detecting apparatus is provided with a sensor detecting unit, a temperature detecting unit, a heater control unit, a change rate calculation unit and a calibration outputting unit. The change rate calculation unit calculates a change rate of a heater current flowing through a heater when a heater control unit maintains the temperature of a sensor cell detected by a temperature detecting unit to be at a target temperature. The calibration outputting unit utilizes a change rate of a heater current to calibrate the sensor output as a sensor current detected by the sensor detecting unit and calculates a sensor calibration output of a gas sensor.