| 摘要 |
<p>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 pressure, the volume of the breath sample may be calculated by integrating the pressure over the time of expiration of the breath sample, 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 pressure and the fuel cell output signal over time, irrespective of the breath sample volume. When the user stops blowing,volume 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.</p> |
