| abstract |
An air flow sensor useable in a drainage apparatus for collecting fluid from a body cavity of a patient by suction, wherein said sensor is adapted to sense the cooling effect of an airflow passing a number of measurement resistors and as an output provide a signal representative of a value of said airflow, and where the resistors is physically arranged on a chip such that when in use the air flow to be measured is flowing over and cooling the resistors, and where a heating resistor is arranged such that air of the air flow to be measured passes at least one measurement resistor before it passes the heater resistor and subsequently at least one other resistor. |