3D FEM-analysis of a Micromachined Wind Sensor Based on a Self-heated Thermistor Array

A. Talic[1], S. Cerimovic[2], M. Mutapcic[2], R. Beigelbeck[1], and F. Keplinger[2]
[1]Institute for Integrated Sensor Systems, Austrian Academy of Sciences, Wiener Neustadt, Austria
[2]Institute of Sensor and Actuator Systems, Vienna University of Technology, Vienna, Austria

We present COMSOL-based analyses and design optimizations of a micromachined wind sensor. The sensor relies on eight germanium thermistors embedded in a thin silicon nitride membrane, where two orthogonally arranged ensembles, each consisting of four thermistors, are connected to form a double Wheatstone-bridge. In operation, each bridge is supplied by a constant current and the self-heating of the thermistors is utilized as heat source.

The developed temperature field depends on direction and magnitude of the fluid flow across the membrane. Evaluating the two bridge voltages facilitates measurement of the flow velocity and direction. The 3D FEM model enables optimized placement and shaping of the thermistors, prediction of the sensor characteristic, and estimation of the excess temperature distribution over the membrane.

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