A 2D particle velocity sensor with minimal flow disturbance

A 2D sound particle velocity sensor, consisting of a cross of two connected, heated wires is presented. We developed a fabrication process by which the wires become freely suspended 350 micrometer above the chip surface. This largely eliminates the influence of boundary layer effects and increases the temperature gradient along the wires, both due to the large distance to the silicon substrate. As a result, the sensor has increased sensitivity and reduced power consumption compared with an earlier design. Furthermore, due to the fully symmetrical structure of the sensor, the sensitive directions are exactly orthogonal to each other and have near identical sensitivity, thus requiring no individual calibration.