Gas Sensor Sweep Control for Charge-Balanced Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing gas sensor control apparatuses face challenges in accurately measuring gas concentration due to charge accumulation caused by impedance measurement, leading to fluctuations in electromotive force, which are difficult to control with existing methods that rely on matching sweep and reverse sweep voltages amidst component tolerances and temperature variations.
Innovation Solution
A control apparatus that adjusts the duration of sweep and reverse sweep periods based on measured current values to maintain charge balance, ensuring accurate gas concentration measurement by promoting charge discharge and minimizing electromotive force fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sweep voltage is applied to measure impedance, then temperature measurement accuracy is improved, but charge accumulates in the gas sensor causing electromotive force fluctuations
Solution Approach 1:
The control apparatus applies a reverse sweep voltage after the normal sweep voltage to pre-emptively discharge accumulated charge from the gas sensor. This counter-action neutralizes the harmful effect of charge accumulation before it can significantly affect electromotive force measurements, thereby maintaining both temperature measurement accuracy and electromotive force stability.
Solution Approach 2:
The system performs periodic impedance measurements using sweep voltage and follows each measurement cycle with a charge discharge phase using reverse sweep voltage. This periodic alternation between measurement and charge neutralization ensures that charge accumulation does not compromise measurement reliability while maintaining the benefits of regular temperature monitoring.
2Reliability
If the absolute values of sweep voltage and reverse sweep voltage are made equal, then charge accumulation is minimized, but component tolerances and temperature variations make exact matching difficult
Solution Approach 1:
The control apparatus measures the actual current values during both sweep and reverse sweep phases, then uses this feedback information to adjust the duration of each phase. By calculating durations based on measured current magnitudes rather than relying on fixed voltage magnitude matching, the system compensates for component tolerances and temperature variations, achieving charge balance despite manufacturing variations.
Solution Approach 2:
Instead of attempting to precisely control voltage magnitudes to be equal (which is affected by component tolerances), the system changes the parameter being controlled from voltage magnitude to time duration. The duration of sweep and reverse sweep periods is adjusted based on measured current values, thereby achieving charge balance through time parameter adjustment rather than voltage parameter matching.
3Measurement precision
If separate temperature sensor is provided, then temperature measurement accuracy is improved, but parts cost increases
Solution Approach 1:
The gas sensor performs multiple functions: it measures both gas concentration (through electromotive force) and temperature (through impedance measurement). By using the existing gas sensor structure for dual purposes rather than adding a separate temperature sensor, the system achieves temperature measurement capability without increasing parts cost, leveraging the sensor's electrical properties for thermometric function.
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 charge accumulation in the gas sensor, allowing for precise gas concentration measurement by maintaining a balance between charge accumulation and discharge, thereby stabilizing the electromotive force and improving measurement accuracy.
Implementation Method 1
a sensor for measuring the oxygen concentration has a solid oxide layer through which oxygen ions can pass, and is configured such as to vary the resulting electromagnetic force in accordance with the oxygen concentration within a detection space
Implementation Method 2
the gas sensor is generally provided with a heater, and the temperature of the gas sensor is adjusted to be held within the activation temperature range by energizing the heater
Implementation Method 3
configured such as to vary the resulting electromagnetic force in accordance with the oxygen concentration within a detection space
Data Source
AI summary
The control section of a control apparatus executes a first control for operating a voltage application section such as to cause a current to flow in a first direction through a gas sensor in a first period, and a second control for operating the voltage application section such as to cause a current to flow in a second direction, opposite to the first direction, through the gas sensor in a second period. The control apparatus changes the length of at least one of the first period and the second period based on a comparison between a first measurement value, which is the absolute value of a value measured by a sweep measurement section during execution of the first control, and a second measurement value, which is the absolute value of a value measured by the sweep measurement section during execution of the second control.