Analysis of the angular sensitivity of an innovative particle velocity sensor

In this paper a novel micromachined acoustic sensor consisting of four heated wires is analyzed theoretically and experimentally. The presence of the chip surface of the probe in the vicinity of the wires influences the local fluid flow, while it also affects the temperature distribution in the probe by altering the direction of heat transport. Both effects result into a specific angular dependence of the sensor sensitivity. To explain this specific directionality of the sensitivity, an analytical model is presented that describes both the air flow around the probe and the temperature profile around the heated wires. Acoustic flow measurements on the probe sensitivity are compared with the theory and with numerical simulations on the device, showing good qualitative and quantitative correspondence.