Gas Sensor Control Unit Noise Suppression
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Solution Overview
Problem
Existing gas concentration sensor systems face challenges in accurately detecting sensor current due to current diversion into capacitors in grounding wires, leading to reduced accuracy in air-fuel ratio detection.
Innovation Solution
A control unit with a sweep circuit, current detection resistor, and protective elements, including capacitors, is designed to supply a variable sweep current and calculate sensor current by accounting for loss currents in protective elements, enhancing accuracy by dividing and managing currents effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If grounding wires with capacitors are connected to the conductive wires, then external noise is suppressed, but sensor current detection accuracy deteriorates due to current diversion into the capacitor
Solution Approach 1:
The grounding system is segmented into multiple grounding wires (first grounding wire and second grounding wire) with separate capacitors (first protective element and second protective element). This segmentation allows independent measurement and compensation of loss currents in each grounding path, enabling accurate sensor current detection while maintaining noise suppression functionality.
Solution Approach 2:
The control unit measures the loss current flowing into the capacitor through the current detection resistor and uses this feedback information to calculate and compensate for the current diversion. By continuously monitoring and adjusting for the loss current, the system maintains accurate sensor current detection despite the presence of capacitive grounding paths.
2Reliability
If a capacitor is provided in the grounding wire to suppress external noise, then noise protection is improved, but the current flowing into the capacitor reduces the accuracy of sensor current measurement
Solution Approach 1:
A current detection resistor is introduced as an intermediary element in the second grounding wire. This resistor enables the measurement of the loss current that flows into the capacitor, providing the necessary information for the control unit to calculate and compensate for the current diversion, thereby maintaining measurement accuracy while preserving noise suppression.
Solution Approach 2:
The system uses the voltage signal from the current detection resistor as feedback to determine the loss current magnitude. The control unit processes this feedback signal to calculate the actual sensor current by compensating for the capacitive current diversion, thus maintaining both noise protection and measurement accuracy.
3Object-affected harmful factors
If multiple grounding wires with protective elements are used, then noise suppression is enhanced, but device complexity increases
Solution Approach 1:
The control unit performs multiple functions using the same measurement infrastructure: it measures the loss current through the current detection resistor, calculates the sensor current with compensation, and determines impedance values. This multi-functionality reduces the need for separate dedicated circuits for each measurement task, thereby limiting the increase in device complexity despite the enhanced grounding structure.
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 configuration significantly improves the accuracy of sensor current detection, enhancing the precision of air-fuel ratio calculations and temperature determination in gas concentration sensors, with a simulated improvement of over ten times in impedance value accuracy compared to previous methods.
Implementation Method 1
The protective elements include a first protective element and a second protective element. The first protective element is provided in the first grounding wire and causes the sweep current supplied from the sweep circuit to be divided to flow to the first protective element and the gas concentration sensor.
Implementation Method 2
The second protective element is provided in the second grounding wire and causes the sensor current flowing in the gas concentration sensor to be divided to flow to the second protective element and the current detection resistor.
Implementation Method 3
a current detection resistor for detecting a sensor current flowing in the gas concentration sensor
Implementation Method 4
a calculation circuit for calculating an impedance of the gas concentration sensor based on the sensor current flowing in the gas concentration sensor and an inter-terminal voltage of the gas concentration sensor
Data Source
AI summary
A control circuit includes a sweep circuit for supplying a sweep current to a gas concentration sensor, a current detection resistor for detecting a sensor current flowing in the gas concentration sensor, a calculation circuit for calculating an impedance of the gas concentration sensor based on the sensor current and an inter-terminal voltage of the gas concentration sensor, and a protective element for suppressing external noise from being applied to the sweep circuit and the calculation circuit. The sweep current is divided to flow in a first protective element and the gas concentration sensor. The sensor current is divided to flow in a second protective element and the current detection resistor. The calculation circuit calculates a loss current flowing to the first protective element or a second loss current flowing to the second protective element and calculates the sensor current based on the calculated current.