Patent ID: 8800344

Claim:
An oxygen sensor arrangement for sensing the oxygen in a breathing loop of a breathing apparatus, which oxygen sensor arrangement comprises: at least one primary oxygen sensor arranged to operatively measure the oxygen in the breathing loop, and a control arrangement for obtaining measures from said oxygen sensor, wherein: said at least one primary oxygen sensor is arranged in a cavity that is in fluid communication with the breathing loop; and said cavity is provided with at least one output orifice for a test channel arrangement, which output orifice is arranged at a position adjacent to, or directly adjacent to said at least one primary oxygen sensor, and said test channel arrangement is adapted to operatively provide a first gas having a first known fraction of oxygen from a first gas supply to said primary oxygen sensor at a position adjacent to or directly adjacent to said primary oxygen sensor, and at least a first test valve arrangement is arranged to operatively open and close the flow of said first gas through said test channel arrangement, and said control arrangement is arranged to operatively actuate said first test valve arrangement so as to provide an amount of said first gas to said primary oxygen sensor via said test channel arrangement, and said control arrangement is arranged to operatively obtain measures from said primary oxygen sensor.