Breath Alcohol Measurement Using Flow-Compensated Fuel Cell Sensing
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Solution Overview
Problem
Existing methods for measuring breath alcohol concentration are either expensive due to high accuracy requirements or bulky due to complex mechanical components, limiting the production of compact, cost-effective devices.
Innovation Solution
A method that calculates the volume of a breath sample by integrating instantaneous flow rate and fuel cell output signals over time, allowing for flow compensation and eliminating the need for predetermined sample volumes, using a pressure-based flow meter and microcontroller to ensure accurate measurements without mechanical sampling systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If infrared spectroscopy sensors are used to measure breath alcohol concentration, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent replaces expensive infrared spectroscopy sensors with disposable or replaceable fuel cell cartridges that contain the sensing element. This allows the main device body to be inexpensive and mass-producible, while the costly sensing component is replaced periodically, effectively resolving the contradiction between measurement precision and device cost.
Solution Approach 2:
The fuel cell sensing element is extracted from the main device body and placed in a separate replaceable cartridge. This separation allows the main device to be manufactured at low cost using simple components, while the expensive fuel cell is contained in a disposable unit that can be replaced rather than integrated permanently.
2Measurement precision
If mechanical sampling systems are used to ensure predetermined breath sample volume, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical sampling systems (motors, solenoid valves, piston-cylinder devices, diaphragm mechanisms) with a simple pressure sensor and electronic control system. The microcontroller regulates breath sample volume by controlling a simple valve based on pressure feedback, eliminating the need for bulky mechanical components while maintaining measurement precision.
Solution Approach 2:
The patent introduces a pressure sensor as an intermediary between the breath sample and the fuel cell. This pressure sensor provides real-time feedback to the microcontroller, which then adjusts the sampling process to achieve the desired volume without requiring complex mechanical sampling systems. The pressure sensor acts as a mediator that enables precise volume control through electronic rather than mechanical means.
3Volume of moving object
If compact device design is implemented without mechanical sampling systems, then device size is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent replaces bulky mechanical sampling systems with electronic pressure-based flow control and integration. The microcontroller integrates the pressure sensor signal over time to calculate breath sample volume, and integrates the fuel cell signal to determine alcohol concentration. This electronic approach enables accurate measurements in a compact device without mechanical components.
Solution Approach 2:
The patent changes the measurement approach from relying on fixed mechanical sampling volumes to using time-integrated pressure and fuel cell signals. By integrating these signals over the duration of the breath sample, the system achieves accurate alcohol concentration measurement regardless of variations in breath flow rate or volume, enabling compact design without sacrificing precision.
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
This approach enables accurate breath alcohol concentration measurement in compact devices with reduced size and cost, capable of handling varying breath volumes and preventing vehicle startup if concentration exceeds a threshold.
Implementation Method 1
measuring the flow rate using a pressure sensor
Implementation Method 2
a fuel cell sensor which converts fuel in the shape of alcohol (ethanol) to electric current in an electrochemical reaction
Data Source
AI summary
The present invention relates to a method and apparatus for measuring breath alcohol concentration of a user. A flow of an expired breath sample is passed through a fuel cell sensor giving an output signal proportional to the amount of alcohol present in the breath sample. By measuring the flow rate, the volume of the breath sample may be calculated, whereas the breath alcohol concentration is calculated based on the fuel cell output signal. Both the sample volume and the breath alcohol concentration values are continually updated by integrating the measured instantaneous flow rate and the fuel cell output signal over time. If the user stops blowing, flow compensation is performed to obtain a compensated fuel cell output signal using a stored calibration volume. Hence, an improved method for accurately measuring the breath alcohol concentration of a test person is achieved, capable of handling varied expired volumes of breath, which obviates the need for a sampling mechanism.