| 主权项 |
1. A breathing apparatus comprising:
at least one delivery device that adds a volume of a substance to a gas flow, said delivery device having a gas inlet and a gas outlet; a monitoring unit configured to monitor a presence of said substance in a gas downstream said delivery device; said monitoring unit comprising a first sensor unit arranged at a first gas conduit at said gas outlet or downstream thereof, said first sensor unit being configured to provide a first measurement value based on at least an acoustic property, such as a sound velocity related property, of a gas present in said first gas conduit; said monitoring unit comprising a second sensor unit arranged at a second gas conduit at said gas inlet or upstream thereof, configured to provide a second measurement value based on at least an acoustic property, such as a sound velocity related property, of a gas present in said second conduit; and said monitoring unit comprising a control unit operatively connected to said first sensor unit and said second sensor unit, and configured to determine said presence of said substance based on a comparison of said first measurement value and said second measurement value, said control unit being configured to compensate for a time delay of gas such that the first measurement value and the second measurement value are determined based on a same gas mass, when said gas is flowing between said first sensor unit and said second sensor unit through said delivery device, in said comparison of measurements. |
