Self Heated Thermo-Resistive Element Hot Wire Anemometer

Sch. of Eng., Griffith Univ., Gold Coast, QLD, Australia
IEEE Sensors Journal (Impact Factor: 1.76). 05/2010; 10(4):847 - 848. DOI: 10.1109/JSEN.2009.2035518
Source: IEEE Xplore


A microelectromechanical systems (MEMS) hot wire anemometer consisting of thermoresistive elements arranged in a differential bridge configuration is presented. The excitation of the elements to the point of self heating allows for dedicated heating elements to be omitted from the device without compromising operation or accuracy. Overall power consumption gives air velocity, and the temperature differential of each element pair is used for wind direction calculation and has demonstrated a sensing resolution better than 1% and a repeatability better than 2%.

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    • "The first uses the front surface of the sensor to sense the wind [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]. In these thermal wind sensors, the heaters and sensing parts are placed on micromembranes and bridges to minimize the heat loss through the substrate [10] [11] [12] [13] [14] [15], whereas others use substrates with low thermal conductivity (i.e. glass [16], porous silicon [17] [18], SU-8 [19], and polyimide [20]) to fabricate the devices. "
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    ABSTRACT: This article describes the design, fabrication, and testing of a self-packaged 2D thermal wind sensor. The sensor consists of four heaters and nine thermistors. A central thermistor senses the average heater temperature, whereas the other eight, which are distributed symmetrically around the heaters, measure the temperature differences between the upstream and downstream surface of the sensor. The sensor was realized on one side of a silicon-in-glass (SIG) substrate. Vertical silicon vias in the substrate ensure good thermal contact between the sensor and the airflow and the glass effectively isolates the heaters from the thermistors. The substrate was fabricated by using a glass reflow process, after which the sensor was realized by a lift-off process. The sensor’s geometry was investigated with the help of simulations. These show that narrow heaters, moderate heater spacing, and thin substrates all improve the sensor’s sensitivity. Finally, the sensor was tested and calibrated in a wind tunnel by using a linear interpolation algorithm. At a constant heating power of 24.5 mW, measurement results show that the sensor can detect airflow speeds of up to 25 m s−1, with an accuracy of 0.1 m s−1 at low speeds and 0.5 m s−1 at high speeds. Airflow direction can be determined in a range of 360° with an accuracy of ±6°.
    Journal of Micromechanics and Microengineering 08/2015; 25(8). DOI:10.1088/0960-1317/25/8/085011 · 1.73 Impact Factor
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    • "using microfabrication techniques to produce miniaturized, low cost, high-performance devices for wind sensing applications. In 2003, Adamec et al. [23], [24] presented a multiaxis HWA fabricated with bulk micromachining and thin film semiconductor technologies. The proposed anemometer consists of thermoresistive elements arranged in a differential bridge configuration, as shown in Fig. 4(b). "
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    ABSTRACT: This paper presents an overview and development of 2-D micromachined thermal wind sensors. It first compares different types of wind sensors, then gives a brief introduction to three basic measurement principles of the thermal wind sensors: hot-wire or hot-film, calorimetric, and time of flight. In order to have a good understanding of development of the 2-D micromachined thermal wind sensors, they are first categorized into thermoresistive, thermoelectric, and thermoelectronic wind sensors based on their operations. Then, each category is further divided into different subcategories, according to their measuring principles and sensor configurations. In Section IV, different materials, fabrication processes, packaging techniques, and control modes of the 2-D micromachined thermal wind sensors are analyzed. This paper also evaluates the core technologies on how to improve the sensitivity, measurement range, and power consumption of the thermal wind sensors.
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