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

Claim 0:
1. A method of measuring a breath alcohol concentration (BrAC) of a user with a reduced lung capacity, the method measuring a flow rate (Q) of a breath sample, the breath sample having a breath sample volume Vb that is variable, the method being performable without a sampling mechanism configured to measure a predetermined sample volume, the method comprising the steps of:
(I) receiving a flow of an expired breath sample from the user into an inlet tube, the inlet tube being adjacent to a proximal end of a first channel;
(II) receiving a first portion of the breath sample from the inlet tube into the first channel at the proximal end, wherein the first channel includes a closed distal end opposite the proximal end, and measuring an instantaneous flow rate (Q) of the first portion of the breath sample with a flow meter, the flow meter being disposed closer to the closed distal end of the first channel than to the proximal end;
(III) triggering a microcontroller in electronic communication with the flow meter to calculate the breath sample volume Vb based on the measured instantaneous flow rate (Q);
(IV) receiving a second portion of the breath sample from the first channel into a second channel at a second channel entrance disposed closer to the proximal end of the first channel than to the distal end, and passing the second portion of the breath sample into a fuel cell sensor in electronic communication with the microcontroller and providing a fuel cell sensor output signal (FCout);
(V) actuating the microcontroller to calculate the breath alcohol concentration (BrAC) based on the output signal (FCout) of the fuel cell sensor;
(VI) updating continually the breath sample volume (Vb) and the breath alcohol concentration (BrAC) via the microcontroller by integrating the measured instantaneous flow rate (Q) and the fuel cell output signal (FCout) over time, irrespective of the breath sample volume (Vb);
(VII) determining, via the microcontroller, an instant at which the flow of the expired breath sample from the user terminates, such that a final collected breath sample volume (Vb) is established; and
(VIII) actuating the microcontroller to compensate the fuel cell sensor output signal (FCout) using a stored calibration volume (Vcal) to obtain a final compensated fuel cell output signal (FCcomp), before calculating the breath alcohol concentration (BrAC) again when the user stops blowing; wherein said compensating is performed using a formula:, F
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 such that the breath alcohol concentration (BrAC) is accurately calculated even when the breath sample volume (Vb) is varied.