A New Approach for Ionic Air Flow Sensors: Transit Time

The new approach results of a basic idea: to get a measure relatively independant of the magnitude of the electrical signals; for this reason the sensor is using the differential transit time from ions between two high transparency grids placed in air flow. A 6 KV short positive pulse is applied to 6 sharp ended pins placed perpendiculary to the air flow producing ions which are flying to a shielding grid under the electrostatic field. After this grid the ions flow at the air speed and induce charges in the measurement grids. The sensor works with a high rate asynchronous sampling system depending of the flow. A simple analogic transform of the 1/T fonction gives a dc output proportionnal to the volumic air flow.