Patent ID: 11885795
Assignee: ALCO SYSTEM SWEDEN AB
Field: Measurement (Instruments)
Classification: CPC G  A  B | IPC A  B  G

Claim 9:
10. An apparatus for measuring breath alcohol concentration (BrAC) of a user with a reduced lung capacity, the device configured to measure a flow rate (Q) of a breath sample, the breath sample having a breath sample volume Vb that is variable, the apparatus being operable without a sampling mechanism configured to measure a predetermined sampling volume, the apparatus comprising:
(I) an inlet tube configured to receive an expired breath sample of a user;
(II) a first channel and a second channel, the first channel having a proximal end adjacent to the inlet tube and a closed distal end opposite the proximal end, the second channel having a second channel entrance disposed closer to the proximal end of the first channel than to the distal end of the first channel;
(III) a flow meter configured to measure an instantaneous flow rate (Q) of a first portion of the breath sample received in the first channel, the flow meter being disposed closer to the closed distal end than to the proximal end;
(IV) a fuel cell sensor in fluid communication with the second channel and configured to measure a second portion of the breath sample received in the second channel at the second channel entrance from the first channel; and
(V) a microcontroller in electronic communication with the flow meter and the fuel cell sensor, the microcontroller being configured to:
(a) calculate the breath alcohol concentration (BrAC) based on an output signal (FCout) of the fuel cell sensor; and
(b) calculate the breath sample volume (Vb) based on the measured instantaneous flow rate (Q);
wherein the microcontroller is further adapted to:
(c) to continually update the breath sample volume (Vb) and the breath alcohol concentration (BrAC) by integrating the measured instantaneous flow rate (Q) and the fuel cell output signal (FCout) over time, irrespective of the breath sample volume (Vb);
(d) determine an instant at which the expired breath sample terminates and calculate the breath sample volume (Vb) at this instant; and
(e) perform a flow compensation to obtain a final compensated fuel cell output signal (FCcomp) using a stored calibration volume (Vcal) wherein said flow compensation is performed using a formula:, F
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