NDIR Breath Sensor Bypass Sampling for Condensation Control
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Solution Overview
Problem
Existing NDIR breath analysis sensors face challenges such as slow response times, high power consumption, narrow operating temperature ranges, and the need for disposable parts, making them unsuitable for real-time and portable applications.
Innovation Solution
A NDIR sensor design with a gas-tight support structure, a hydrophilic or hydrophobic window, and a heating element on the window to prevent condensation, combined with a breath sampling apparatus that bypasses most of the gas to minimize moisture and thermal shock exposure, allowing for fast and accurate CO2 measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mainstream sampling is used where the entire breath passes through the sample cell, then the sensor can detect gas concentration, but the sensor becomes vulnerable to water condensation and requires disposable parts and high power consumption
Solution Approach 1:
The breath sampling flow is segmented into two separate paths: a main flow that bypasses the sensor and a small sample flow that passes through the sensor. This segmentation allows the sensor to detect gas concentration while protecting it from water condensation by exposing it to only a minimal amount of moist breath air.
Solution Approach 2:
The harmful effect (water condensation) is extracted and separated from the measurement function. By taking out the majority of the breath air through the bypass route, only the essential gas sampling function remains in the sensor path, eliminating the condensation problem while maintaining detection capability.
2Reliability
If heaters and disposable elements are used to deal with water condensation, then the sensor can operate in humid environments, but power consumption increases and device complexity increases
Solution Approach 1:
The harmful water vapor is extracted from the sensor path by routing the majority of breath air through a bypass. This eliminates the need for heaters or disposable desiccant elements, achieving operation in humid environments without the associated power consumption and device complexity.
Solution Approach 2:
The invention eliminates the need for disposable elements like water traps and sampling tubes by using a permanent bypass route design. This reduces both operational cost and device complexity while maintaining reliability in humid conditions.
3Measurement precision
If the entire breath passes through the sample cell, then gas concentration can be measured, but the sensor experiences thermal shock and slow response time
Solution Approach 1:
The breath flow is segmented into a main bypass flow and a small sensor sample flow. This segmentation reduces the thermal mass and moisture load on the sensor, enabling faster response time while maintaining accurate gas concentration measurement through the sample path.
Solution Approach 2:
Instead of exposing the sensor to the full breath flow (excessive action), only a partial sample flow is directed through the sensor. This partial action is sufficient for accurate measurement while dramatically improving response time by reducing thermal shock and moisture exposure.
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 achieves fast response times (<1 second), low power consumption, and wide temperature operation, enabling portable and cost-effective breath analysis without the need for replaceable parts, suitable for consumer-level use in various environments.
Implementation Method 1
A Nondispersive Infrared (NDIR) sensor measures absorption of IR (infrared) light within narrow wavelength range between the source and the detector due to presence of the gas of interest
Implementation Method 2
a heating element on the window to prevent condensation
Data Source
Figure 1~2
Figure 3A~3C
Figure 3D~4
AI summary
A gas sensor has a light detector, a gas-tight support structure enclosing the light detector, a window positioned in said support structure, and a light source mounted to the support structure. A sample area is positioned in the support structure to receive a gas to be tested. The light source is aligned with the window, sample area, and the light detector to pass light from the light source through the gas in the sample area to the light detector. The sensor can be provided in a breadth sampling apparatus that has deflects gas to a bypass route so that only a portion of gas reaches the sensor.