Flow sensor instrumentation employing differential pressure reading

This paper presents an analysis of flow sensors found in the market today that uses the differential pressure technology to measure flow at mechanical pulmonary ventilator respiratory circuits. It proposes a set of differential pressure transducers for the reading of the resistance element in order to get a readout resolution equal or smaller than 0.15L/min within the regular measuring range for mechanical ventilation, which is from 0 to 150L/min. It also suggests an internal geometry for the resistance element to reduce pneumatic noise in the differential pressure measuring. In this paper is shown a decrease on the standard deviation value of the differential pressure reading for the same ranges in the same test condition. It is shown that the proposed geometry for the new nozzle decreases the measurement pneumatic noise in 47.5% in average. Finally, it is shown that the combination of three differential sensors, reading different ranges, achieves the desired resolution and measuring range.