Resistive Gas Sensor Frequency Counting for Wide Resistance Range
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Solution Overview
Problem
Conventional gas sensors have limited measurable resistance ranges and sensing resolutions due to linearity issues with resistance dividers, and require additional analog-digital converters to process analog sensing voltages, increasing manufacturing costs.
Innovation Solution
A resistive gas sensor with a sensing circuit and determination circuit that performs frequency-division operations on detection signals to generate digital signals representing gas concentrations, allowing for a wide measurable resistance range and consistent sensing resolutions across different gas concentrations without the need for additional analog-digital converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistance divider is used to obtain sensing voltage, then the gas sensor can detect resistance changes, but the linearity is limited and the measurable resistance range is restricted
Solution Approach 1:
The patent changes the measurement parameter from voltage (analog) to frequency (digital). By measuring the frequency of oscillation in an RC circuit where the sensing element is one of the resistors, the system achieves a wide measurable resistance range while maintaining high precision. The frequency is inversely proportional to the resistance, providing a linear relationship that resolves the linearity limitation of voltage-based methods.
2Use of energy by moving object
If the sensing voltage level closes to the rail voltage, then the voltage range is maximized, but the sensing resolution is compressed and degraded
Solution Approach 1:
The patent replaces the voltage-based analog measurement system with a frequency-based digital measurement system. Instead of measuring voltage levels that compress near rail voltages, the system measures the frequency of oscillation generated by the RC circuit. This substitution eliminates the voltage compression problem entirely, as frequency measurement remains linear and precise across the entire resistance range.
3Extent of automation
If an analog-digital converter is added to convert sensing voltage to digital signal, then digital processing can be performed, but the manufacturing cost increases
Solution Approach 1:
The patent makes the sensing circuit self-converting by generating a digital frequency signal directly from the resistance measurement. The RC oscillation circuit naturally produces a frequency output that is directly proportional to the resistance value, eliminating the need for external analog-to-digital conversion. The microprocessor can directly read and process this digital frequency signal, achieving full digital operation without adding costly converter 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
The solution provides improved linearity and wider measurable resistance ranges, enabling accurate digital signal generation for gas concentration determination without increasing manufacturing costs, thus enhancing the sensing capabilities of gas sensors.
Implementation Method 1
The determination circuit performs a frequency-division operation on the detection signal with a frequency-division parameter to generate a frequency-division signal
Implementation Method 2
counts a half of a period of the frequency-division signal to generate a half-period count value
Data Source
AI summary
A resistive gas sensor is provided. The resistive gas sensor includes a sensing circuit and a determination circuit. The sensing circuit senses a gas to generate a detection signal. The determination circuit performs a frequency-division operation on the detection signal by a frequency-division parameter to generate a frequency-division signal, counts a half of a period of the frequency-division signal to generate a half-period count value, and determines concentration of the gas according to the half-period count value. The determination circuit determines the frequency-division parameter according to the half-period count value.