Gas Sensor Analog Feedback Circuit for Temperature Control
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Solution Overview
Problem
Existing gas sensors that heat a temperature sensing element with a heater resistor require increased digital processing complexity and circuit scale to control current accurately, leading to errors and slow response times to ambient temperature changes.
Innovation Solution
A gas sensor design incorporating a feedback circuit with a reference resistor and amplifier to control current in the heater resistor based on ambient temperature, allowing for constant temperature heating of the sensing element without digital processing, and an additional amplifier circuit to regulate current in a second heater resistor for precise gas concentration measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital processing (AD conversion, calculation, DA conversion) is used to control current in the heater resistor, then current control accuracy can be improved, but circuit scale increases and response speed decreases
Solution Approach 1:
The patent replaces the digital processing system (AD converter, calculator, DA converter) with an analog feedback circuit system. The feedback circuit directly controls the current in the heater resistor through analog voltage feedback, eliminating the need for digital-to-analog conversion and significantly reducing circuit complexity while maintaining control accuracy.
Solution Approach 2:
The patent employs a feedback circuit that monitors the voltage at the connection point between the reference resistor and the first temperature sensing element, and automatically adjusts the current in the heater resistor to maintain constant temperature. This continuous feedback mechanism enables accurate current control without requiring complex digital processing.
2Measurement precision
If digital processing (AD conversion, calculation, DA conversion) is used to control current in the heater resistor, then current control accuracy can be improved, but response speed to ambient temperature changes decreases
Solution Approach 1:
The patent replaces the sequential digital processing operations (AD conversion, calculation, DA conversion) with a parallel analog feedback circuit that responds immediately to temperature changes. The feedback circuit continuously monitors and adjusts the heater current in real-time, providing fast response to ambient temperature changes without the time delays inherent in digital conversion processes.
3Stability of the object's composition
If ambient temperature sensing element is added to control heater current, then constant temperature heating can be achieved, but circuit complexity increases due to required digital processing
Solution Approach 1:
The patent merges the ambient temperature sensing function with the existing feedback circuit by utilizing the same feedback mechanism. The feedback circuit monitors the voltage division ratio between the reference resistor and the first temperature sensing element, which naturally reflects ambient temperature changes, and automatically adjusts the heater current accordingly. This integration eliminates the need for separate digital processing circuits.
Solution Approach 2:
The feedback circuit serves multiple functions: it monitors the temperature of the first temperature sensing element, detects ambient temperature changes through voltage division ratio changes, and controls the heater current to maintain constant temperature. This multi-functional approach reduces circuit complexity by eliminating the need for dedicated ambient temperature sensing and digital processing components.
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 design enables high-accuracy, high-speed control of current in the heater resistor, reducing circuit complexity and improving response times to ambient temperature changes while maintaining precise gas concentration measurement.
Implementation Method 1
a first temperature sensing element Rd1 having a resistance value that changes according to ambient temperature
Implementation Method 2
a first heater resistor MH1 for heating the first temperature sensing element Rd1
Implementation Method 3
a second temperature sensing element Rd2 whose resistance value changes according to the concentration of a gas to be measured
Implementation Method 4
a second heater resistor MH2 for heating the second temperature sensing element Rd2
Data Source
AI summary
A gas sensor includes a feedback circuit part and a sensor circuit part. The feedback circuit part includes a reference resistor and a first temperature sensing element which are connected in series, a first heater resistor that heats the first temperature sensing element, and a first amplifier circuit that controls the amount of current to flow in the first heater resistor based on an internal potential. The sensor circuit part includes a second temperature sensing element and a second heater resistor that heats the second temperature sensing element. A current according to the output of the first amplifier circuit flows in the second heater resistor. With this configuration, it is possible to automatically change the amount of current to flow in the second heater resistor according to ambient temperature without digital processing to thereby heat the second temperature sensing element to a constant temperature.