NDIR Breath Sensor Bypass Sampling for Fast Moisture-Resistant Detection
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Solution Overview
Problem
Existing NDIR sensors for breath analysis face challenges such as slow response time, high power consumption, narrow operating temperature range, need for periodic recalibration, and the use of disposable parts, making them unsuitable for portable and consumer-level applications.
Innovation Solution
A gas sensor design featuring a gas-tight support structure with a hydrophilic or hydrophobic window and a heating element to prevent condensation, combined with a bypass route to minimize moisture exposure to detectors, allowing for fast response times and low power consumption, and a sampling system that balances airflow to ensure accurate 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 gas concentration can be measured, but the sensor becomes exposed to moisture and contamination causing slow response time and requiring disposable parts
Solution Approach 1:
The sampling system is divided into two separate paths: a mainstream path for breath discharge and a sample path for gas sampling. The sample path includes a sample cell that is spatially separated from the main breath flow, allowing gas concentration measurement while protecting the sensor from moisture and contamination. This segmentation enables fast response time by preventing moisture accumulation on the sensor.
Solution Approach 2:
A bypass channel acts as an intermediary element that allows a portion of the breath gas to reach the sensor without requiring the entire breath to pass through the sample cell. The bypass channel connects the mainstream sampling path to the sample path, enabling controlled gas flow to the sensor while minimizing moisture exposure and maintaining fast response time.
2Object-affected harmful factors
If heaters and disposable elements are used to deal with water condensation, then condensation can be managed, but power consumption increases and device complexity increases
Solution Approach 1:
The harmful effect of water condensation is extracted and isolated from the sensor by using a hydrophobic window that repels moisture. The condensation management function is removed from the sensor interior and transferred to the external hydrophobic coating, which prevents water accumulation without requiring internal heaters or disposable elements, thereby reducing power consumption and device complexity.
Solution Approach 2:
The surface properties of the window are changed by applying a hydrophobic coating, which alters the interaction between water and the window surface. This parameter change (surface hydrophobicity) prevents condensation formation without requiring thermal heating, eliminating the need for power-consuming heaters while effectively managing water condensation.
3Ease of manufacture
If replaceable plastic parts are used in the sample cell, then the cell can be replaced when dirty, but the device requires disposable parts increasing cost and complexity
Solution Approach 1:
The sample cell is designed with a permanent hydrophobic window that provides self-cleaning properties by repelling moisture and contamination. This self-service characteristic eliminates the need for disposable replaceable parts, as the window maintains its functionality over time without requiring user intervention or replacement, thereby reducing device complexity and eliminating disposable component requirements.
4Weight of moving object
If the sensor is designed for portable applications, then the device can be compact, but the operating temperature range becomes narrow
Solution Approach 1:
The window material properties are changed by selecting materials with appropriate thermal and hydrophobic characteristics that enable operation across a wide temperature range. This parameter change in material selection allows the compact portable sensor to function reliably in diverse environmental conditions without requiring temperature control mechanisms, maintaining both portability and wide temperature operation.
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, low-cost breath analysis without the need for replaceable parts, suitable for real-time monitoring in various environments.
Implementation Method 1
A gas sensor design featuring a gas-tight support structure with a hydrophilic or hydrophobic window and a heating element to prevent condensation
Implementation Method 2
A gas sensor design featuring a gas-tight support structure with a hydrophilic or hydrophobic window and a heating element to prevent condensation
Implementation Method 3
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
Data Source
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.