Patent ID: 7063669

Claim:
A spirometer, comprising: a. a housing having an elongated flow chamber at one end, a pressure sensing end opposite said one end, and an outlet passageway intercepting said flow chamber at an angle α; b. a differential pressure sensor coupled to said pressure sensing end of said flow chamber at an angle β to an axis along a length of said flow chamber, said differential pressure sensor closed to air flow therethrough, said differential pressure sensor is coupled to said flow chamber by meander passageway through which only diffusion of air takes place and whose length divided by the speed of sound is less than a measuring rate of said differential sensor and said meander passageway is bent to inhibit contaminants from said flow chamber from reaching said differential pressure sensor; wherein said angle α is substantially greater than 0° but substantially less than 180° and wherein said angle β is equal to or greater than 90° and less than or equal to 180°.