A two dimensional ionic anemometer for very low flow rates

A two-dimensional double-cage flow meter for detecting very small rates of airflow using ionized air is demonstrated. A corona discharge inside a Faraday cage generates an ion cloud that expands outside the Faraday cage driven only by its own charge in the absence of any external electric field. Due to its slow movement, the cloud is highly sensitive to the movement of the gas matrix. The use of four collector electrode grids at 0°, 90°, 180° and 270° allows for precise determination of the vector of the airflow. The method proves to be linear and suited for flow rates at least between 0 and 1.6 m/s. It is also shown that Debye shielding reduces the effect of external electric fields on the ions while the charge of the cloud itself significantly influences its movement. Despite this, efficient control of the ions by external electric fields is possible.