Abstract
Flow sensing in hostile environments is of increasing interest for applications in the automotive, aerospace, and chemical and resource industries. There are thermal and non-thermal approaches for high-temperature flow measurement. Compared to their non-thermal counterparts, thermal flow sensors have recently attracted a great deal of interest due to the ease of fabrication, lack of moving parts and higher sensitivity. In recent years, various thermal flow sensors have been developed to operate at temperatures above 500 °C. Microelectronic technologies such as silicon-on-insulator (SOI), and complementary metal-oxide semiconductor (CMOS) have been used to make thermal flow sensors. Thermal sensors with various heating and sensing materials such as metals, semiconductors, polymers and ceramics can be selected according to the targeted working temperature. The performance of these thermal flow sensors is evaluated based on parameters such as thermal response time, flow sensitivity. The data from thermal flow sensors reviewed in this paper indicate that the sensing principle is suitable for the operation under harsh environments. Finally, the paper discusses the packaging of the sensor, which is the most important aspect of any high-temperature sensing application. Other than the conventional wire-bonding, various novel packaging techniques have been developed for high-temperature application.
Highlights
Micro-Electro-Mechanical Systems (MEMS) sensors such as pressure, temperature, strain, acceleration and flow are essential for many harsh environment applications
The operation of thermoresistive flow sensors at high temperatures is a challenging task with many factors to be considered such as: (i) the stability of the sensor; (ii) quick response time; (iii) low power consumption; (iv) superior sensitivity; (v) low cost; and (vi) small size. These factors are primarily determined by the choice of the material as: (i) it reduces the drift and provides less sensitivity to environmental effects; (ii) excellent mechanical properties such as high elastic modulus and yield strength providing a robust resistive bridge during the compressive fluid flow; and (iii) it avoids the breakage of bridges due to oxidation at high temperatures
Various studies on the development characterization of thermal flow sensors in different are placed inside the channel for packaging.and
Summary
Micro-Electro-Mechanical Systems (MEMS) sensors such as pressure, temperature, strain, acceleration and flow are essential for many harsh environment applications. Thermal flow sensors more often find applications in harsh environments than non-thermal sensors because of their fast response and the lack of moving parts. Micro-Electro-Mechanical Systems (MEMS) technology allows for the fabrication of miniaturized sensors with extraordinary performance in terms of sensitivity, response time, cost-effectiveness and thermal flow sensors with extraordinary performance in terms of sensitivity, response time, power consumption [22]. In the past two decades, research groups around the world have developed a number of thermal flow sensors for various applications. There has been to date no comprehensive article reviewing the progress in the development of harsh environment thermal flow sensors.
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