Papers by Keyword: Capacitive Pressure Sensor

Abstract: In this paper, the thermo-mechanical modelling of an entire sensor structure, under hydrostatic pressure, is carried out using commercial FEM software COMSOL multiphysics. A comparison of the obtained results with those found in the literature, allows us to corroborate the well-known models. Furthermore, the design of high performance conventional silicon-based pressure sensors for low-pressure biomedical applications has been achieved by optimizing the influencing parameters on the two features mentioned above.For a specific biomedical application, a complete analysis, considering the impact of the device thickness, embedding type and diaphragm material, has shown that the highest performances are reached for a silicon diaphragm thickness of 65μm, a circular shape having a radius of 1750μm and a cavity thickness of 4.6μm. Simulation results show that the sensor under investigation yields a quasi linear response with pressure values lying in the range [0 ÷70kPa]. The pressure sensitivity is about 2 pF/bar, and the thermal drift is about 16 ppm/°C for a temperature range [-20°C÷ 150°C]. The obtained results may well contribute to the optimization of the device’s performances and can provide to the designer several chosen criteria for a given application.

Abstract: The novel flexible pressure sensor with skin-like stretchability and sensibility has attracted tremendous attention in academic and industrial world in recent years. And it also has demonstrated great potential in the applications of electronic skin and wearable devices. It is significant and challenging to develop a highly sensitive flexible pressure sensor with a simple, low energy consuming and low cost method. In this paper, the silver nanowires (AgNWs) as electrode material were synthesized by polyol process. The polydimethylsiloxane (PDMS) was chosen as a flexible substrate and polyimide (PI) film as dielectric layer. The AgNWs based electrode was prepared in two methods. One is coating the AgNWs on photographic paper followed by in situ PDMS curing. Another one is suction filtration of the AgNWs suspension followed by glass slide transfer and PDMS curing. Then the capacitive pressure sensor was packaged in a sandwich structure with two face to face electrodes and a PI film in the middle. The sensitivity of the sensor as well as the micro-structure of the electrodes was compared and studied. The results indicate that the roughness of the electrode based on AgNWs/PDMS micro-structure plays an important role in the sensitivity of sensor. The as-prepared flexible pressure sensor demonstrates high sensitivity of 0.65kPa^-1. In addition, the fabrication method is simple, low energy consuming and low cost, which has great potential in the detection of pulse, heart rate, sound vibration and other tiny pressure.

Abstract: An approach providing a digital output linearly proportional to capacitance difference for capacitive pressure sensor is presented. Based on sigma-delta (ΣΔ) technique, the structure is insensitive to circuit imperfections and component mismatch, permitting the realization of digitized capacitive sensor readout with good accuracy. Analysis shows that a resolution as high as 20 bits is achievable. Simulation results are given to confirm the effectiveness.

Abstract: In the paper, a Double-notches Touch Mode Capacitive Pressure Sensor (DTMCPS) is presented. The sensor employs a special SiC-AlN-SiC sandwich structure to achieve high-accuracy pressure measurement in high-temperature environment. The simulation analysis to the relation of capacitance and external pressure of the sensor shows that the sensor has higher sensitivity and longer linear range than traditional one. At the same time, the technical process of the sensor has been designed in the paper. The research shows that DTMCPS packaged in a high-temperature ceramic package can withstand higher temperature. Consequently, the sensor can be applied in high-temperature and harsh environment.

Abstract: Smart sensor systems that can operate at high temperatures are required for a range of aerospace applications such as propulsion [1]. For future aerospace propulsion systems to meet the requirements of decreased maintenance, improved performance, and increased safety, the inclusion of intelligence into the propulsion system design and operation is necessary. This implies the development of sensor systems able to operate under the harsh environments present in an engine. Likewise, applications such as Venus exploration missions require systems that can operate in the harsh environments present on the Venus planetary surface. More sensor systems added to the aircraft increases the number of wires and the associated weight, complexity, and potential for failure. Thus, there is a need not only for high temperature sensors and electronics, but also for high temperature wireless technology. This implies the integration of sensors, electronics, wireless circuits, and power into a single system. In this paper, we demonstrate a significant step towards this goal, i.e., for the first time the integration of a pressure sensor with a SiC JFET logic-gate ring oscillator that operates at 500 °C; the sensor output signal is extracted from the small-signal ring oscillation frequency detected at the powersupply end of the DC power wires.

Abstract: In this paper, simulation solution for Microelectromechanical systems (MEMS) based capacitive differential pressure sensor for aircraft altimeter is proposed. The principle of proposed MEMS capacitive differential pressure sensor design was explained. Analysis for the measurement of center deflection and capacitive sensitivity square diaphragm membrane was done. Simulation on deflection and capacitive sensitivity was carried out for the range of pressure from 100mbar to1100mbar. Gold, diaphragm membrane was used in this analysis. Analysis result shows, linear variation on center deflection and capacitance variation which is more suitable for this application.

Abstract: In order to reveal the temperature dependence of a touch mode capacitive pressure sensor, temperature dependence of material parameters of the sense have been studied. Using Finite Element Method (FEM) to simulate and solve capacitance, the results show that the relation of capacitance and temperature is almost linear in touch state of the sensor. At the same time, temperature sensitivities under different pressure are slight difference, which are 0.0056pF/K and 0.0040pF/K, respectively. Therefore, the high-temperature performance of the sensor is greatly outstanding.

Abstract: Single crystal silicon diaphragms are widely used as pressure sensitive elements in micromachined pressure sensors. When designing such a sensor it is usual to assume that the silicon is an isotropic material and the average elastic constants are used. However, the mechanical properties of single crystal silicon are orthotropic, and this has an important effect on the mechanical behaviour of silicon diaphragms under pressure. In this work, the deflections of orthotropic silicon circular diaphragms which are orientated against the (100) and the (110) planes are presented. It is found that by assuming silicon is isotropic material, the maximum stress is underestimated by 9.4% for (110) orientated silicon diaphragms, while the maximum stress is underestimated by 8% for (100) orientated silicon diaphragms. Therefore, when a silicon diaphragm is used in a MEMS sensor, the orthotropic properties should be taken into account for accuracy. Finally, the performance of a capacitive sensor is predicted by using finite element method.