Gas Sensor Oxygen Pumping Control for Detection Accuracy
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Solution Overview
Problem
Conventional gas sensors experience a decrease in detection accuracy of specific gas concentrations due to the pump-in control voltage when oxygen is pumped into the periphery of the reference electrode, affecting the potential difference between electrodes and thereby reducing the accuracy of gas concentration measurements.
Innovation Solution
A gas sensor design that includes a layered body with oxygen ion-conductive solid electrolyte layers, a reference electrode, a measurement electrode, 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, ensuring a first period with a large potential difference and a second period with a falling potential difference, satisfying the ratio T2/Tf ≥ 1, which helps maintain detection accuracy by minimizing residual voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control voltage is applied to pump oxygen to the reference electrode, then oxygen concentration reduction is compensated, but detection accuracy decreases due to potential change
Solution Approach 1:
The control voltage is applied periodically rather than continuously, creating alternating first and second periods. During the first period, the control voltage is applied to pump oxygen to the reference electrode. During the second period, the control voltage is stopped and detection is performed. This periodic action allows the system to compensate for oxygen concentration reduction while minimizing the impact of control voltage on detection accuracy.
Solution Approach 2:
Oxygen is pumped to the reference electrode in advance during the first period before detection is performed in the second period. This preliminary action ensures that oxygen concentration is compensated and stabilized before the detection measurement begins, thereby improving reliability without compromising measurement precision.
2Reliability
If control voltage is applied continuously, then oxygen pumping is effective, but residual voltage affects detection accuracy
Solution Approach 1:
The control voltage is applied periodically with distinct first and second periods. The first period applies control voltage for oxygen pumping, while the second period stops the control voltage to allow residual voltage to subside before detection. This periodic action resolves the contradiction between maintaining effective oxygen pumping and ensuring accurate detection by separating these functions in time.
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 design effectively compensates for oxygen concentration reductions in the reference electrode's periphery, reducing the impact of pump-in control voltage on detection accuracy and enhancing the measurement of specific gas concentrations, particularly NOx concentrations, by maintaining high accuracy during the second period with reduced residual voltage.
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
Implementation Method 3
a layered body that is formed by stacking a plurality of oxygen ion-conductive solid electrolyte layers
Data Source
AI summary
A method of operation of a gas sensor includes applying a control voltage that is set between the reference electrode and the measurement-object gas side 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. Tf, a fall time of the potential difference between the first period and the second period, and T2, a second time that is a length of the second period, satisfies Tf≤T2.