Optical Gas Sensor ON/OFF Sampling for Higher SNR
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Solution Overview
Problem
Existing sensor systems, such as NDIR gas sensors, face challenges in improving the signal-to-noise ratio (SNR).
Innovation Solution
A sensor system that computes measurement values using signals detected during both ON and OFF intervals of the light-emitting element, with a duty cycle of 50% or more, and performs weighting to cancel out noise variations, utilizing a computation device to enhance SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional correlated double sampling is used for noise reduction, then measurement capability is maintained, but signal-to-noise ratio is insufficient due to inability to handle momentary dark current changes
Solution Approach 1:
The light emitting element operates in periodic ON/OFF cycles with specific duty ratios (50% or more), enabling systematic collection of multiple OFF interval signals. This periodic operation allows the computation device to gather multiple dark current samples that can be averaged to reduce momentary noise variations, directly improving SNR while maintaining measurement reliability
Solution Approach 2:
The system performs preliminary noise characterization by collecting multiple OFF interval signals before computing the final measurement value. By pre-acquiring multiple dark current samples and averaging them, the system prepares a more accurate baseline that effectively compensates for momentary dark current changes, thereby improving the signal-to-noise ratio of the final measurement
2Measurement precision
If multiple OFF interval signals are collected and averaged, then signal-to-noise ratio is improved, but measurement time increases
Solution Approach 1:
The system dynamically adjusts the duty ratio (keeping it at 50% or more) and the number of OFF intervals used for averaging based on the specific measurement requirements and noise conditions. This dynamic parameter adjustment allows optimization of the balance between measurement time and SNR improvement, enabling the system to adaptively find the optimal trade-off point for different operating conditions
3Productivity
If duty cycle is increased to maintain measurement speed, then measurement efficiency is improved, but noise averaging capability is reduced
Solution Approach 1:
The system changes the duty ratio parameter to 50% or more, which provides sufficient OFF interval time for collecting multiple dark current samples while maintaining adequate measurement speed. This specific parameter setting enables the system to achieve both good noise averaging capability (by having enough OFF intervals) and acceptable measurement efficiency (by not making the ON interval too short), resolving the contradiction between these two requirements
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 system achieves improved SNR by reducing noise through averaging and weighting, resulting in enhanced measurement accuracy and reliability.
Implementation Method 1
uses absorption characteristics of infrared light in the gas in order to detect the concentration of the gas
Implementation Method 2
improves the signal-to-noise ratio by averaging noise over multiple OFF intervals
Data Source
AI summary
Provided is a sensor system having an improved SNR. The sensor system (1) includes: a sensor (gas sensor 10) including a light-emitting element (11) and a detecting element (light-receiving element 12) that detects a signal that is based on light emitted from the light-emitting element; and a computation device (20) that, by taking an interval in which the light-emitting element emits light as an ON interval and an interval in which the light-emitting element does not emit light as an OFF interval, uses the signal as detected in the ON interval and the signal as detected in a plurality of the OFF interval to compute one measurement value.