Gas Sensor Reference Electrode Potential Stabilization
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Solution Overview
Problem
The detection accuracy of specific gas concentrations in gas sensors can be decreased due to the pump-in control voltage when oxygen is pumped into the periphery of the reference electrode, causing changes in the potential of the reference electrode and affecting the voltage between the reference and measurement electrodes.
Innovation Solution
A gas sensor design that includes a layered body with oxygen ion-conductive solid electrolyte layers, a reference electrode, a measurement electrode, a measurement-object gas side electrode, a reference gas introducing portion, and a reference gas regulating device that applies a control voltage repetitively set to on and off states to pump oxygen to the reference electrode, allowing detection of specific gas concentrations during a second period when the potential difference is minimized, thereby reducing the impact of the control voltage on detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a control voltage is applied between the reference electrode and the measurement-object gas side electrode to pump oxygen to the periphery of the reference electrode, then the oxygen concentration in the reference electrode periphery is maintained, but the potential of the reference electrode changes, decreasing the detection accuracy of the specific gas concentration
Solution Approach 1:
The control voltage is applied in a periodic manner with alternating first and second periods. During the first period, the control voltage is applied to pump oxygen to the reference electrode periphery. During the second period, the control voltage is not applied, allowing the potential of the reference electrode to stabilize. This periodic application enables both oxygen concentration maintenance and accurate gas concentration detection.
Solution Approach 2:
Oxygen is pumped to the periphery of the reference electrode in advance during the first period before the detection phase. This preliminary oxygen supply ensures that when the control voltage is not applied during the second period, the oxygen concentration is already maintained, preventing detection accuracy degradation while allowing potential stabilization.
2Quantity of substance
If a control voltage is applied to pump oxygen to the reference electrode, then oxygen depletion in the reference gas is compensated, but the voltage between the reference electrode and the measurement electrode changes, affecting detection accuracy
Solution Approach 1:
The control voltage application is divided into periodic first and second periods. During the first period, oxygen is pumped to compensate for oxygen depletion. During the second period, no control voltage is applied, allowing the voltage between electrodes to stabilize for accurate detection. This periodic approach separates the oxygen compensation function from the detection function in time.
Solution Approach 2:
The control voltage is dynamically adjusted between application and non-application states. The system transitions from a state where control voltage is applied (oxygen pumping active) to a state where control voltage is not applied (detection phase), optimizing both oxygen supply and measurement conditions at different times.
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 suppresses the decrease in detection accuracy caused by the pump-in control voltage, ensuring high accuracy in measuring specific gas concentrations by maintaining a low residual voltage during the second period, allowing for precise detection of gas concentrations like NOx in exhaust gases.
Implementation Method 1
a reference gas regulating device that applies a control voltage that is repetitively set to on state and off state between the reference electrode and the measurement-object gas side electrode to pump in oxygen to the periphery of the reference electrode
Implementation Method 2
The gas sensor detects the specific gas concentration in the measurement-object gas on the basis of an electromotive force generated between the reference electrode and the measurement electrode
Data Source
AI summary
A method of operation of a gas sensor includes applying a control voltage that is repetitively set to on state and off state between the reference electrode and the measurement-object gas side electrode to pump in oxygen to the periphery of the reference electrode; and detecting the specific gas concentration in the measurement-object gas on the basis of a voltage between the reference electrode and the measurement electrode during a second period, from among a first period that is started upon setting of the control voltage to on state, during which a potential difference between the reference electrode and the measurement-object gas side electrode is large, and the second period that is started upon setting of the control voltage to off state after the potential difference falls from the first period.