Air flow measurement is an important task in many fields including process control, air conditioning systems, environmental monitoring, medical instrumentation, weather forecasting system and so forth. For many years, flow sensing was accomplished by means of large-scale mechanical flow meters such as anemometers, turbines and Pitot tubes. In recent years, many researchers have applied micromachining processes to realizing micro sensors and arrays for measuring air flow parameters. Many previous studies have demonstrated successful application of micro electro-mechanical system (MEMS) techniques to the fabrication of variety of flow sensors capable of detecting both flow rate and flow direction.
MEMS-based sensors have advantages of small size and light weight. They can briefly be divided into two categories: mechanical sensors and thermal sensors.
Recently, multi-sensor integrated technology has become fashionable in the sensor domain. This sensor shows the merits of both a drag force flow sensor and a thermal flow sensor by integrating them to obtain high sensitivity over a wide range. Although it is sensitive to both low and high rate, it has both mechanical and thermal parts.
Rim Chang Sik, a researcher at the Semiconductor Institute, has proposed a cantilever-based air flow sensor for measuring flow-rate and flow-direction simultaneously using only a mechanical part without a thermal one.
The sensing device is comprised of a standing cylinder-cantilever and an MEMS-based silicon diaphragm with eight diffused piezoresistors as sensing elements.
The device is effective to exactly determine air flow direction angle and to expand operation range with relatively simple structure.
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