Switchable Amplifier Circuit for Gas Sensor Accuracy
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Solution Overview
Problem
Existing gas concentration measuring apparatuses for automotive engines are inefficient due to the use of multiple amplifiers, leading to increased size and complexity, which hinders accurate air-fuel ratio measurement across a wide range, especially in stoichiometric and lean air-fuel ratio control systems.
Innovation Solution
A gas concentration measuring apparatus with a solid electrolyte gas sensor, a current-measuring resistor, an amplifier circuit with operational amplifiers and resistors, and a switch that adjusts the amplification factor by distributing resistors as input and feedback resistors, allowing for precise control of measurement resolution without the need for multiple amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple amplifiers with different amplification factors are installed in the output stage of the sensor control circuit, then the accuracy in determining the air-fuel ratio within two ranges (wide air-fuel measuring range and narrow air-fuel ratio measuring range) is improved, but the size of the sensor control circuit and the number of input/output terminals increase
Solution Approach 1:
The patent applies the dynamics principle by implementing a switchable amplifier circuit that can dynamically change its amplification factor based on the required measurement range. The amplifier circuit includes a switch that can connect different resistor configurations to the operational amplifier, allowing the system to transition between high-gain mode for narrow range measurements and low-gain mode for wide range measurements. This dynamic reconfiguration eliminates the need for multiple fixed amplifiers while maintaining measurement accuracy across different air-fuel ratio ranges.
Solution Approach 2:
The patent applies the universality principle by designing a single amplifier circuit that can perform multiple functions through switchable resistor configurations. Instead of having separate amplifiers for different measurement ranges, the invention creates one universal amplifier that can adapt its gain factor by reconfiguring its internal resistor connections. This multi-functional design reduces the overall component count and circuit complexity while achieving the same measurement capabilities as multiple specialized amplifiers would provide.
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 solution enhances measurement accuracy across a wide air-fuel ratio range, reduces the size and complexity of the sensor control circuit, and enables effective stoichiometric and lean air-fuel ratio control, as well as sensor diagnosis during fuel cut-off conditions.
Implementation Method 1
a gas sensor equipped with a sensor element which is made of a solid electrolyte and works to produce a sensor current upon application of voltage thereto as a function of a concentration of a selected gas
Implementation Method 2
an amplifier circuit equipped with an operational amplifier and a plurality of amplifying resistors, the amplifier circuit working to amplify the sensor current, as measured through the current-measuring resistor
Data Source
AI summary
A gas concentration measuring apparatus for use in air-fuel ratio control of automotive engines is designed to determine the concentration of oxygen within a wide and a narrow range using a sensor current flowing through a sensor element. The apparatus includes an amplifier circuit equipped with an operational amplifier and a plurality of amplifying resistors and a switch. The switch is responsive to a request signal to switch a relation in electrical connection between an operational amplifier and the amplifying resistors to distribute the amplifying resistors into an input resistor and a feedback resistor for the operational amplifier to change an amplification factor of the amplifier circuit. This results in a change in resolution of measurement of the concentration of oxygen, thereby ensuring enhanced accuracy in determining the concentration of oxygen in a selected one of the narrow and wide ranges.