Oxygen monitor and warning device for an aircraft breathing system

Abstract

In an aircraft breathing system a sensor assembly for monitoring the concentration of oxygen in a source of breathable fluid supplied to a recipient. The sensor assembly has a housing with a chamber therein connected by a conduit to the source of breathable fluid. A restricted orifice member in the conduit allows a sample of the breathable fluid to continually flow into the chamber while an exit port in the housing allows the sample of breathable fluid to flow to the surrounding environment. A sensor responsive to the partial pressure of oxygen is connected to the chamber. The sensor in response to the partial pressure of the oxygen produces an operational signal. The operational signal activates an indicator to provide the recipient with a reading of the concentration of oxygen in the breathable fluid. An aneroid fixed to the housing has a face that engages a seat surrounding the exit port. Whenever the aircraft is above a predetermined altitude to establish a constant absolute pressure for the sample in the chamber. This constant absolute pressure stabilizes the operation of the sensor and thereby maintains a uniform indication of the percentage of oxygen in the breathable fluid above the predetermined altitude.