referring to the drawing in particular , an oxygen supply device , in which an oxygen mask 2 is connected by a line to an oxygen bottle 4 , is shown schematically . on an oxygen outlet 6 of the oxygen bottle 4 , a shut - off valve 8 and a pressure reducer 10 are arranged directly one after the other in a manner known per se in the flow direction . the shut - off valve 8 is used to open and close the oxygen bottle 4 . by using the pressure reducer 10 , the oxygen pressure prevailing in the oxygen bottle 4 , which can be more than 100 bar , is reduced to an average pressure of about 2 to 3 bar . on the outlet side , the pressure reducer 10 has a line connection to the oxygen mask 2 . the oxygen mask 2 is constructed as a half mask and has a mask body 12 covering mouth and nose . on the outside of the mask body 12 there is arranged a component 14 , which contains an electronic breathing regulator 16 , an air mixing valve 18 and an inhalation valve 20 . the component 14 has a hollow cylindrical base body 22 , in the interior of which the breathing regulator 16 is arranged at an end facing away from the mask body 12 . via a supply line 24 led through the base body 22 , the oxygen inlet of the breathing regulator 16 is connected by a line to the oxygen outlet of the pressure reducer 10 . on the outlet side of the breathing regulator 16 , that is to say downstream of an oxygen outlet , not illustrated in the figure , of the breathing regulator 16 , the base body 22 of the component 14 forms an unoccupied internal space or mixing chamber 26 . in the exemplary embodiment illustrated in the figure , the air mixing valve 18 is arranged on the outside of the base body 22 , in the region of the internal space 26 . via an aperture 28 provided downstream of the breathing regulator 16 on the circumferential wall of the base body 22 , the air mixing valve 18 has a flow connection to the internal space 26 of the base body 22 . the air mixing valve 18 has a flow inlet 30 communicating with the surroundings of the oxygen mask 2 . the flow inlet 30 of the air mixing valve 18 is closed by a valve body 32 in the form of a diaphragm . in this case , the valve body 32 is forced by a helical spring 34 into a position closing the flow inlet 30 . the inhalation valve 20 is likewise arranged outside the base body 22 of the component 14 in the exemplary embodiment illustrated . the inhalation valve 20 has a flow connection to the internal space 26 of the base body 22 via a flow duct 36 . the flow duct 36 is arranged at the end of the base body 22 that is at a distance from the breathing regulator 16 in the longitudinal direction of the base body 22 . the inhalation valve 20 has a flow outlet 37 , which opens in the interior of the body 12 of the oxygen mask 2 . the outlet on the downstream side of the flow duct 36 is closed by a valve body 38 arranged in the inhalation valve 20 . in this case , the valve body 38 is prestressed by means of a helical spring 40 in the direction of the narrow section 36 . in the interior of the mask body 12 there is arranged an exhalation valve 42 . the valve housing of the exhalation valve 42 is divided by a diaphragm 44 into two valve parts 46 and 52 that are separated fluidically from each other . in this case , a first valve part 46 forms a flow path from an inlet opening 48 in the internal space of the mask body 12 to a large number of outlet openings 50 , which are arranged on the outside of the mask body 12 . a second valve part 52 communicates via a bypass duct 54 with the flow duct 36 , the flow duct 36 and the bypass duct 54 connecting the internal space 26 of the component 14 in a fluidically conductive manner to the second valve part 52 of the exhalation valve 42 . arranged in the second valve part 52 of the exhalation valve 42 is a spring component 56 . in interaction with a positive pressure prevailing in the internal space 26 of the component 14 with respect to the internal mask pressure , the diaphragm 44 having the spring component 56 is prestressed into the closed position of the exhalation valve 42 . in the internal space or mixing chamber 26 of the base body 22 , an oxygen sensor 58 is arranged downstream of the air mixing valve 18 and downstream of the aperture 28 . the oxygen sensor 58 has a signal connection to a control device 62 via an electric line 60 . the control device 62 has a display function by means of a monitor 64 , which is connected to the control device 62 by an electric line 66 . furthermore , an ambient pressure sensor 68 has a signal connection to the control device 62 via a line 70 , and a pressure sensor 72 arranged in the interior of the mask body 12 has a signal connection to the control device 62 via a line 74 . the pressure sensor 72 is used to register the internal mask pressure , which changes cyclically because of the successive inhalation and exhalation phases . on the basis of the pressure values provided by the pressure sensor 72 , the control device 62 is able to drive the breathing regulator 16 in a timed manner in such a way that the requisite quantity of oxygen is available to the user of the oxygen supply device at the start of inhalation . in the following text , the functional monitoring of the oxygen supply device according to the invention will be described by using the drawing figure . by means of the ambient pressure sensor 68 , the flight - altitude - dependent air pressure prevailing in the cockpit of an aircraft is measured . on the basis of the pressure values determined by the ambient pressure sensor 68 , the control device 62 determines the oxygen demand of the user of the oxygen supply device and sets the opening times of the breathing regulator 16 appropriately . as a result , desired values for the oxygen partial pressure that are proportional to the opening times result in the internal space 26 of the component 14 . the real or actual values of the oxygen partial pressure are registered by the oxygen sensor 58 and compared with the desired values by the control device 62 . if the desired and actual values of the oxygen partial pressure agree , this indicates a satisfactory operating behaviour of the oxygen supply device . if the pressure values determined by the oxygen sensor 58 lie below the desired values predefined by the control device 62 , this means an inadequate oxygen supply to the user of the oxygen supply device . this deficient supply can be attributed to a malfunction of one or more of the components connected upstream of the oxygen sensor 58 in the flow direction . in detail , this can mean that the oxygen bottle 4 can be empty , shut - off valve 8 , pressure reducer 10 , breathing regulator 16 or air mixing valve 18 have a defect or there is a leak along the flow path from the oxygen bottle 4 to the oxygen sensor 58 . if an excessively low actual value of the oxygen partial pressure has been determined by the control device 62 with the aid of the oxygen sensor 58 , this is displayed on the monitor 64 by the control device so that it is easily visible by the user of the oxygen supply device . the latter can then immediately use a replacement device for the oxygen supply . while a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention , it will be understood that the invention may be embodied otherwise without departing from such principles .
an oxygen supply device , preferably a pilot oxygen supply device , has an oxygen source and at least one oxygen mask . a breathing regulator is arranged between the oxygen source and the oxygen mask . an oxygen sensor is arranged downstream of this breathing regulator .