NOx Exhaust Sensor Temperature Compensation via Heater Voltage Drop
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Solution Overview
Problem
Exhaust gas sensors, such as nitrogen oxide sensors, experience measurement inaccuracies due to increased temperatures in the area of electrical leads and housing, leading to distorted temperature profiles and altered electrode cooling, which affect the accuracy of nitrogen oxide concentration detection.
Innovation Solution
Determine the voltage drop between the heating device's electrical supply line and measuring line, compare it with a reference voltage to calculate a compensation voltage, and use this to correct the nitrogen oxide value by assigning it to a compensation nitrogen oxide value, thereby compensating for temperature-induced measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heating device heats the sensor element to maintain operating temperature, then the sensor can operate at the required temperature, but the electrical leads and housing experience increased temperature leading to measurement inaccuracies
Solution Approach 1:
A temperature compensation mechanism is introduced as an intermediary between the heating device and the measurement system. The compensation voltage, derived from the voltage drop across the heating section, serves as a mediator to correct the measurement values affected by temperature variations in the electrical leads and housing.
Solution Approach 2:
The invention changes the parameter being measured by introducing a compensation voltage that accounts for temperature effects. Instead of directly measuring nitrogen oxide concentration, the system measures the voltage drop across the heating section, uses it to calculate compensation voltage, and then applies this compensation to the original measurement to obtain the corrected nitrogen oxide value.
2Temperature
If additional external heat input from exhaust gas flows around the sensor, then the sensor operates at required temperature, but the electrodes become warmer than initial state causing increased signal and excessively high nitrogen oxide values
Solution Approach 1:
The invention converts the harmful effect of temperature-induced voltage changes in electrical leads into a beneficial compensation mechanism. The voltage drop across the heating section, which initially causes measurement errors, is now used to calculate the compensation voltage that corrects these errors, turning a source of inaccuracy into a tool for improving accuracy.
3Temperature
If the temperature profile at the tip of the sensor element is altered due to disrupted heat dissipation, then the pump electrode becomes cooler than the measuring electrode, but this leads to measurement error in detected nitrogen oxide concentration
Solution Approach 1:
The system implements a feedback mechanism where the voltage drop across the heating section is continuously monitored, and the resulting compensation voltage is fed back to correct the nitrogen oxide measurements. This closed-loop approach ensures that temperature variations are continuously compensated for, maintaining measurement accuracy despite changes in the temperature profile.
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 method improves the accuracy of nitrogen oxide concentration measurements by accounting for temperature variations in the sensor element's electrical leads and housing, ensuring more precise detection of nitrogen oxide levels.
Implementation Method 1
A heating device is also arranged in the main body, designed to heat the main body to and maintain a predetermined operating temperature, for example, approximately 850°C
Implementation Method 2
Exhaust gas sensors, such as nitrogen oxide sensors, can be based on the amperometric principle, i.e., an electrochemical method for the quantitative determination of chemical substances
Implementation Method 3
determining a measuring voltage that drops between the first electrical conductor and the measuring conductor... determining a compensation voltage by calculating the difference between a predetermined reference voltage and the determined measuring voltage
Data Source
Figure 1
Figure 2~3
AI summary
The present invention relates to a method for determining a state parameter of an exhaust gas sensor (10) which has a sensor element (12) and a heating device (60) which is arranged in the sensor element (12) and is intended to heat the sensor element (12). The heating device (60) comprises a heating section (62) which is arranged in the sensor element (12) and is electrically connected, via a first electrical line (64) and a second electrical line (66), to a control device for electrically controlling the heating section (62). The heating device (60) also comprises a measuring line (68) which is electrically connected between the control device and the first electrical line (64) and can be used to control the temperature-dependent resistance of the heating section (62). The method according to the invention comprises determining a measurement voltage which is dropped between the first electrical line (64) and the measuring line (68), determining a compensation voltage on the basis of a predetermined reference voltage and the determined measurement voltage, and determining the state parameter of the exhaust gas sensor (10) by assigning the determined compensation voltage to the state parameter.