Sensor Internal Resistance Measurement via Charge Displacement Segmentation
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Solution Overview
Problem
Existing methods for determining the internal resistance of sensor elements, such as lambda probes, are inaccurate due to the influence of charge transfer and capacitive effects caused by current pulses, which are not fully accounted for when connected to engine control systems via low-pass filters.
Innovation Solution
The method involves applying a current pulse to the sensor element and measuring the increase in electrical voltage at multiple points during charge transfer, allowing for the separation of ohmic and polarization-related components, thereby providing a more precise determination of internal resistance by accounting for capacitive effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current pulse is applied to the sensor element to determine internal resistance, then the internal resistance can be measured, but charge displacement and capacitive effects cause voltage increase that leads to measurement inaccuracy
Solution Approach 1:
The voltage increase is segmented into two distinct components: an ohmic component (immediate voltage increase) and a polarization-related component (delayed voltage increase due to charge displacement). By separating these components temporally and analytically, the method isolates the accurate ohmic measurement from the harmful capacitive effects.
Solution Approach 2:
The method performs preliminary analysis of the voltage-time characteristic curve to identify and separate the ohmic component before the full polarization effect develops. By evaluating the immediate voltage increase at the start of the current pulse, the method captures the accurate internal resistance value before charge displacement significantly affects the measurement.
2Object-affected harmful factors
If the electrical voltage is recorded three milliseconds after current load begins to filter high-frequency interference, then signal interference is reduced, but the charge displacement effect influences the internal resistance determination result
Solution Approach 1:
The method performs the critical measurement of the ohmic component at the very beginning of the current pulse, before the 3-millisecond delay that would introduce charge displacement effects. This preliminary action captures the accurate internal resistance value before both high-frequency interference and capacitive effects significantly impact the measurement.
Solution Approach 2:
The method dynamically evaluates the voltage-time characteristic curve, adapting the measurement timing to the specific electrical behavior of the sensor element. By analyzing the temporal development of voltage and identifying the ohmic component's time window, the method optimizes the measurement point to avoid both high-frequency interference and charge displacement effects.
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 enables a more accurate determination of internal resistance, improving the reliability of sensor element diagnostics and temperature stabilization, which enhances signal accuracy and extends the sensor's service life.
Implementation Method 1
The current load on the sensor element causes a charge displacement within the sensor element, which can lead to an increase in the electrical voltage between the first and second electrodes
Implementation Method 2
As soon as the oxygen concentration in a cavity approaches zero, the Nernst potential rises sharply and partially compensates for the applied voltage
Data Source
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AI summary
The present invention relates to a method for determining an internal resistance of a sensor element (110) for sensing a proportion of a gas component from a gas mixture in a measurement gas compartment, which method is intended to make it possible to determine the internal resistance of the sensor element (110) as accurately as possible. The sensor element (110) has at least one cell (114), wherein the cell (114) comprises at least one first electrode (116), at least one second electrode (118) and at least one solid electrolyte (120) which connects the first electrode (116) and the second electrode (118), and wherein an electrical voltage (124) is applied between the first electrode (116) and the second electrode (118). According to the present method, the following steps are carried out: a) a current pulse (130) is applied to the sensor element (110), wherein the current pulse (130) causes a charge displacement to occur in the sensor element (110), wherein the occurrence of the charge displacement increases the electrical voltage (124) between the first electrode (116) and the second electrode (118); b) a value for the increase in the electrical voltage (124) between the first electrode (116) and the second electrode (118) is determined; wherein step b) is carried out at least twice at different times during the occurrence of the charge displacement and a value for the increase in the electrical voltage (124) is determined therefrom at the different times in each case, and step c) is carried out as follows: c) the internal resistance of the sensor element (110) is determined from the values for the increase in the electrical voltage (124) which are determined at the different times during the occurrence of the charge displacement.