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ABSTRACT: An integrated CMOS-compatible Pirani vacuum sensor system has been developed in this paper, which consists of a tungsten microhotplate array with four same microhotplates in series, a constant current circuit, an 8-b A/D converter, and a digital interface. With a tiny amount of the external components, a gas pressure between 10<sup>-1</sup> and 10<sup>5</sup> Pa can be sampled, digitized, and real-time displayed by a LED. It can also be transferred to an external process unit, which makes it suitable for application in a gas pressure control system. The sensor system is implemented in a 0.5-μm CMOS process. When the sensor system works at 5-V voltage and 2.5-MHz clock input, the total power consumption is 350 mW, and the temperature increase of each microhotplate is 35°C.
Journal of Microelectromechanical Systems 09/2011; · 2.10 Impact Factor
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ABSTRACT: This paper reports a tungsten microhotplate fabricated in a standard CMOS process and the implementation of a MicroPirani pressure sensor with it. A monolithic constant-current circuit including an operational amplifier is used to bias the tungsten microhotplate to measure the gas pressure. The sensor shows a linear response to the gas pressure in the range of 1-100 Pa when driven by a constant current of 7 mA. In this regime, the sensitivity of the sensor is 0.23 mV/Pa, the linearity is 4.95%, and the hysteresis is 8.69%. The MicroPirani pressure sensor in this paper can be used in a medium-vacuum measurement. Because tungsten in a standard CMOS process has a large temperature coefficient regardless of the different manufacturing processes, the design of the tungsten microhotplate can be applied to other thermal-based sensors, even in different standard CMOS processes.
IEEE Transactions on Industrial Electronics 05/2009; · 5.16 Impact Factor
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ABSTRACT: The paper presents a CMOS-compatible micro-Pirani sensor which consists of the tungsten micro-hotplate and the constant current circuit based on the operational amplifier. The advantage of the constant current circuit for the micro-Pirani sensor is that it is more sensitive than the constant temperature one in the low gas pressure. The micro-Pirani system is implemented in an industrial 0.5-mum CMOS process. The measurement results show that the designed micro-Pirani sensor has a good response to the gas pressure, especially in the low gas pressure ranging from 1 Pa to 100 Pa, the sensitivity of the sensor is 0.23 mV/Pa and the linearity is 4.95%.
Micro Electro Mechanical Systems, 2009. MEMS 2009. IEEE 22nd International Conference on; 03/2009
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ABSTRACT: A microbridge is a basic micro-electro-mechanical systems (MEMS) device and has great potential for application in microsensors and microactuators. The thermal behavior of a microbridge is important for designing a microbridge-based thermal microsensor or microactuator. To study the thermal behavior of a microbridge consisting of Si3N4 and polysilicon with a 2 µm suspended gap between the substrate and the microbridge while the microbridge is heated by an electrical current fed through the polysilicon, a microbridge model is developed to correlate theoretically the input current and the temperature distribution under the buckling conditions, especially considering the effects of the microscale gaseous thermal conduction due to the microbridge buckling. The calculated results show that the buckling of the microbridge changes the microscale gaseous thermal conduction, and thus greatly affects the thermal behavior of the microbridge. We also evaluate the effects of initial buckling on the temperature distribution of the microbridge. The experimental results show that buckling should be taken into account if the buckling is large. Therefore, the variation in gaseous thermal conduction and the suspended gap height caused by the buckling should be considered in the design of such thermomechanical microsensors and microactuators, which requires more accurate thermal behavior.
Smart Materials and Structures 01/2008; 17(1):015036. · 2.09 Impact Factor
