Breath testing instrument, to measure the alcohol level, deflects part of the exhaled air towards a semi-conductor sensor with a variable conductivity to give sound wave amplitudes proportional to the alcohol gas content present

摘要

Instrument to detect the presence of a gas, in exhaled breath blown into a chamber, has a hollow and cylindrical mouthpiece (1) with an inlet (9) and an outlet (10). A second outlet (2) carries a portion of the exhaled air flow towards the monitor (13), which registers any gas in the breath. Instrument to detect the presence of a gas, in exhaled breath blown into a chamber, has a hollow and cylindrical mouthpiece (1) with an inlet (9) and an outlet (10). A second outlet (2) carries a portion of the exhaled air flow towards the monitor (13), which registers any gas in the breath. The system measures the exhaled air flow rate, to ensure that the gas level is monitored only when a given volume of air has been exhaled. The monitor has a thin layer semi-conductor sensor, where its conductivity varies according to the level of gas present and in contact with it. The semi-conductor is heated by a resistance heater, embedded in the semi-conductor, to raise it to a given temperature level. The measurement of the exhaled air is indicated by the amplitude of the air flow sound wave passing through the second outlet at an acoustic receiver (20).