Oxygen Sensor Reference Cell Timing Against Noise-Induced Offsets
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Solution Overview
Problem
Existing oxygen sensor systems face accuracy degradation and reduced reliability due to noise-induced consistent offsets in temperature measurements, which affect air-fuel ratio monitoring and long-term sensor performance.
Innovation Solution
Incorporating a random time delay in impedance measurement intervals to prevent synchronization of noise with measurement commands, thereby eliminating consistent offsets and improving temperature control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If periodic impedance measurements are performed at fixed time intervals, then temperature control feedback is provided to the control loop, but noise-induced consistent offsets in temperature measurements occur when noise frequency is an integer multiple of measurement frequency
Solution Approach 1:
The patent applies the dynamics principle by transitioning from fixed periodic impedance measurements to randomised measurement intervals. The measurement time intervals are varied randomly around a nominal value, preventing synchronous alignment between measurement commands and periodic noise signals. This dynamic adjustment of measurement timing eliminates consistent temperature offsets caused by noise while maintaining adequate temperature control feedback.
2Productivity
If impedance measurements are performed at high rate (100-800 times faster than thermal time constant), then adequate feedback is provided to control loop, but synchronization with noise frequency causes consistent temperature offsets
Solution Approach 1:
The patent maintains high measurement productivity by performing impedance measurements at 100-800 times the thermal time constant rate, but introduces dynamic variation in measurement intervals. Instead of uniform periodic measurements, the interval between consecutive measurements is randomly adjusted, ensuring sufficient feedback frequency for control loop operation while preventing synchronous alignment with noise signals that would cause consistent temperature offsets.
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
The random delay component ensures accurate temperature measurement and control, reducing noise-induced errors and enhancing the reliability of air-fuel ratio monitoring and long-term sensor performance.
Implementation Method 1
A lambda sensor is based on a solid-state electrochemical fuel cell. Its two electrodes provide an output voltage corresponding to the quantity of oxygen in the exhaust relative to that in the atmosphere.
Implementation Method 2
current is sent through the pump cell. Depending on the direction and amount of current, oxygen ions can be pumped into or out of the measurement chamber to return the measurement cell voltage to 450 mV.
Implementation Method 3
cell impedance measurements are performed on an O2 Sensor in order to estimate its temperature
Data Source
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AI summary
An oxygen sensor system includes an oxygen sensor (1) and associated circuitry (2,3) connected thereto. The oxygen sensor (1) including a reference cell (4). The associated circuitry (2,3) measures the impedance of the reference cell (4) at time intervals, wherein the time intervals include a random component.