GAS CONCENTRATION AND/OR FLOW SENSOR

摘要

A gas concentration and/or bulk flow rate sensor suitable for measuring the oxygen concentration and the bulk flow rate of gas delivered to a patient for medical purposes. Two piezoelectric transducers mounted on a printed circuit board are interconnected by an elongated coiled tube. The gas is flowed around one of the transducers, through the tube and around the other transducer. Periodically, one of the transducers is energized with a single short duration pulse to transmit a sonic wave through the gas to the other transducer. The travel time for the sonic wave is measured. The two transducers are alternately used as transmitters and receivers so that the wave travel time is measured both with and against the gas flow direction. A thermistor is located in the center of the coiled tube for measuring the temperature of the gas. From the measured times, the measured temperature and stored formulas, a microprocessor calculates the oxygen concentration and/or the bulk flow rate for the gas. The sensor also may be used to measure other components of a gas mixture.