NDIR Gas Sensor with Reflected Light Substrates
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Solution Overview
Problem
Conventional nondispersive infrared (NDIR) gas sensors require multiple components and complex signal processing due to the need for band-pass filters and light sources at specific wavelengths, leading to measurement errors and difficulties in temperature compensation, especially when the light source intensity changes.
Innovation Solution
A gas sensor design featuring a first and second sensor unit with identical temperature characteristics, where light from a single light source is reflected and received on adjacent substrates, eliminating the need for band-pass filters and simplifying the configuration, allowing for accurate temperature compensation and reduced measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If band-pass filters and multiple light sources are used to detect gas concentration, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the band-pass filter component from the optical path. Instead of using filters to select specific wavelengths, the system uses a single light source that emits broadband infrared radiation and detects absorption at the specific wavelength (e.g., 4.3 μm for CO2) directly through the sensor, eliminating the need for complex filtering mechanisms while maintaining measurement accuracy
Solution Approach 2:
The sensor design makes the single sensor unit serve multiple functions: it detects both the reference light intensity and the absorbed light intensity at the target wavelength. By measuring the ratio of these intensities, the system achieves both reference measurement and absorption measurement capabilities with a single sensor, reducing overall device complexity
2Reliability
If multiple independent sensors are used for reference and detection, then temperature compensation is improved, but device complexity increases
Solution Approach 1:
The patent merges the reference sensor and detection sensor into a single sensor unit. This unified sensor simultaneously measures both the reference light intensity (without absorption) and the absorbed light intensity (with absorption), enabling temperature compensation and gas concentration measurement to be performed with one component rather than two independent sensors, thereby reducing system complexity while maintaining reliability
3Measurement precision
If light source intensity is increased to improve signal detection, then measurement sensitivity is improved, but measurement error increases due to drift
Solution Approach 1:
The system implements a feedback mechanism by continuously measuring the reference light intensity and using it to normalize the absorbed light intensity measurement. The gas concentration is calculated based on the ratio of absorbed intensity to reference intensity, which automatically compensates for light source intensity drift and maintains measurement stability over time without requiring additional active control components
Solution Approach 2:
The system performs preliminary measurement of the reference light intensity before calculating the absorbed light intensity. By establishing the baseline reference level first, the system can then accurately determine absorption based on the ratio, which pre-compensates for any light source variations and prevents measurement errors before they occur
4Adaptability or versatility
If band-pass filters are used to select specific wavelength, then wavelength selectivity is improved, but device complexity and size increase
Solution Approach 1:
The patent removes the band-pass filter from the optical system. Instead of using physical filters to select specific wavelengths, the system uses a single broadband infrared light source and relies on the sensor's ability to detect absorption at the specific target wavelength (e.g., 4.3 μm for CO2) directly, eliminating the need for complex wavelength filtering mechanisms while maintaining wavelength selectivity through the absorption characteristics of the target gas
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 design results in a compact, reliable gas sensor with reduced measurement errors and simplified configuration, capable of accurately detecting gas concentrations without the need for additional filters or complex calibration.
Implementation Method 1
An optical gas sensor includes a light source for emitting a wavelength that can be absorbed by molecules of a gas to be measured, and a sensor to detect a signal thereof. The environmental gas significantly absorbs light with wavelengths around several micrometers
Implementation Method 2
a first sensor unit and a second sensor unit disposed to receive light output from a first light source... light from a single light source is reflected and received on adjacent substrates
Data Source
AI summary
A small-size reliable gas sensor that can reduce a measurement error can be provided. The gas sensor includes a first light source; a first sensor unit and a second sensor unit disposed to receive light output from the first light source; a first substrate having a first principal surface on which the first light source and the first sensor unit are provided; and a second substrate having a first principal surface on which the second sensor unit is provided. The first sensor unit is disposed at a location where light output from the first light source and reflected on the second principal surface strikes the first principal surface of the first substrate.