Capacitive Differential Pressure Research Articles

A new automatic measurement system for high-speed railway substructure settlement based on hydrostatic pressure difference levelling

Exact settlement measurement of substructures plays an important role in their status detection throughout all-life-cycle of high-speed railway. A Hydrostatic Pressure Difference Levelling system (HPDL) is developed based on the mechanism that pressures of any two points at different elevations in incompressible static liquid are different. The approach accounts for a hyperbolic variation in the density of the pressure transmission liquid with temperature, variation in the earth’s gravitational field and the elevation at the measurement point. High accuracy capacitive differential pressure transmitters are adopted owing to their high sensitivity, temperature-insensitive, low energy consumption, and sensing stability. The HPDL results are verified with settlement values measured by the precise level. It was demonstrated that the HPDL results correlate well with the precise level and can be considered as an effective method to measure the settlement of high-speed railway substructures.

Modeling analysis and fabrication of MEMS capacitive differential pressure sensor for altimeter application

This paper proposes the modeling analysis of MEMS highly sensitive Capacitive Differential Pressure Sensor (CDPS) and also the development of a fabrication process for CDPS structures for aircraft altimeter applications. Highly sensitive CDPS structure models using circular and square sandwich polyimide diaphragm membranes, with and without center boss, were adopted, whereas other studies report on silicon diaphragms. CDPS characterization was carried out to analyze the deflection sensitivity, capacitive sensitivity, stress on diaphragm membrane and the effect of temperature on capacitive sensitivity. Simulation results of square diaphragm without center boss show better characteristics than other proposed diaphragm structures. This design yields 145.8 nm/mbar and 0.574 fF/mbar of deflection and capacitive sensitivity, respectively. The maximum stress developed on the diaphragm at maximum working pressure is less than the yield stress of polyimide material by a factor of 1.77 and capacitive sensitivity deviates at ±0.00195%/°C. From the modeling analysis, square diaphragm CDPS structure yields better characteristics and hence the fabrication process for CDPS has been developed, and its fabrication process flow verified using Intellisuit virtual fab tool.

차압식 유량계를 실장을 위한 Single Capacitive Type Differential 압력 센서 개발

차압식 유량계를 실장을 위한 Single Capacitive Type Differential 압력 센서 개발

Modeling and analysis of MEMS capacitive differential pressure sensor structure for altimeter application

This paper presents the capacitive differential pressure sensor (CDPS) structure modeling, diaphragm material selection for CDPS and the analysis on deflection and capacitive sensitivity. Principle of CDPS was explained for the proposed model, whereas earlier works reports on absolute pressure sensing techniques. Simple and sandwich diaphragm structure for the CDPS was also proposed and its deflection characteristics was analyzed. Five different CDPS structure was modeled ranging from simple to complex structure. Simulation was carried out for the differential pressure range from ź56 mbar to 900 mbar, used to study centre deflection sensitivity and capacitive sensitivity for the proposed CDPS structure models for altimeter application. From the simulation results it was observed, that model 3-high sensitive CDPS structure with polyimide sandwich diaphragm structure meets the desired requirement and shows center deflection sensitivity of 148.4 nm/mbar and capacitive sensitivity of 0.574 fF/mbar.

The study of data fusion for high suspended sediment concentration measuring using the IGA-RBF method

To optimize the radial basis function (RBF), an improved genetic algorithm (IGA) was used for measuring high suspended sediment concentration (HSSC) in the Yellow River. The improved probabilities crossover and mutation were utilized to realize the twin goals of maintaining diversity in the population and sustaining the convergence capacity of the GA, and a new method was proposed to resolve the problem of deciding the optimal values of the probabilities of crossover and mutation. In this method, the effects of environmental factors, such as temperature, depth and flow rate on the capacitive differential pressure (CDP) sensors, were discussed. To compare the fusion effect of the IGA-RBF method, the sediment concentration data were fused and processed using unary linear regression (ULR), multiple linear regression (MLR), back propagation (BP) neural network, standard RBF (S-RBF) methods, adaptive GA-optimized RBF (AGA-RBF) and dynamic GA-optimized RBF (DAGA-RBF). The results show that the IGA-RBF method can effectively eliminate environmental influences and raise the measuring accuracy and stability of the system.

Study on MEMS Capacitive Differential Pressure Sensor

The design and fabrication of MEMS capacitive differential pressure sensor is reported. Silicon membrane is used as movable electrode. Gold metal film on glass is used as fixed electrode. Anodic bonding is used to bond together the silicon and glass to form the capacitive pressure sensor. The measurement capacitance of the sensors is 5.37 pF at an applied pressure of 0 kPa and 7.26 pF and the full operating range of 40 kPa.The ratio of changed to initial capacitance was 0.35. The error of the MEMS capacitive pressure sensor is less than 4‰ full-scale(FS) by using quadratic curve fitting which can meet most application requirements.

Modeling and Analysis of High Sensitive MEMS Capacitive Differential Pressure Sensor with Polymide Diaphragm

Modeling and Analysis of High Sensitive MEMS Capacitive Differential Pressure Sensor with Polymide Diaphragm

Study on the flow behavior in spout-fluid bed with a draft tube of sub-millimeter grade silicon particles

An experimental study on gas-particle flow behavior in a spout-fluid bed with a draft tube was performed in a 182mm diameter cylindrical column with a flat distributor. Sub-millimeter grade silicon particles with wide particle size distribution were used as bed materials to investigate the effect of operating conditions and geometrical parameters on the flow behavior. The pressure drop and its standard deviation were recorded using a capacitive differential pressure transducer, which can be applied to evaluate the hydrodynamic properties. The effects of fluidizing gas and geometrical parameters of the bed on the hydrodynamic characteristics were analyzed. The results show that the minimum spout-fluidizing velocity increases with increasing the length of entrainment zone and the draft tube diameter, but it decreases with the increasing of fluidizing gas flow rate and static bed height. Furthermore, a correlation on the minimum spout-fluidizing velocity which has practical value is proposed based on the present experimental data, and the calculated data is in good agreement with the experimental results. In addition, seven flow regions can also be observed in different spouting and fluidizing gas velocity, and a new flow regime map for a spout-fluid bed is established with the consideration of the influence of flow regime on geometrical parameters. Such results mentioned above can provide important information on the flow behavior in the spout-fluid bed with a draft tube for process design.

Identification and Compensation of A Capacitive Differential Pressure Sensor Based on Support Vector Regression Using Particle Swarm Optimization

Abstract Capacitive Differential Pressure Sensors (CDPSs) are highly utilized in industry. However, the accuracy of CDPSs is limited because of the adverse effects of ambient temperature on their output characteristics. In this paper, the effect of temperature on a CDPS output is identified and compensated for using a Support Vector Machine for Regression (SVR) method. To achieve a better performance, a Particle Swarm Optimization (PSO) method is employed to optimize the parameters of SVR. Also, a test bench is designed and implemented to obtain data under real environmental conditions. The experimental results obtained verify the performance of modeling and compensation for the non-linear behavior of the CDPS based on SVR using PSO. Simulation results show that the proposed identifier and compensator estimates and compensates the output accurately. Finally, the performances of the proposed methods are also compared with those of Artificial Neural Network (ANN) techniques.

Design Analysis of MEMS Capacitive Differential Pressure Sensor for Aircraft Altimeter

Design Analysis of MEMS Capacitive Differential Pressure Sensor for Aircraft Altimeter

Simulation Analysis of MEMS Based Capacitive Differential Pressure Sensor for Aircraft Application

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.

Application of Data Fusion Based on Least Squares in Sediment Concentration Data Processing

In the process of measuring the sediment concentration in flow-water, the temperature in the water will greatly influence the output of the capacitive differential pressure sensor. This paper uses least squares method to fuse the results of experiment to eliminate influence of the temperature and depth． The system uses value of the capacitive differential pressure sensor, the temperature sensor and the depth sensor as input . This paper particularly introduces principle of the least squares method, PLC hardware design and multi-channels data fusion technology. The results indicate that data fusion method based least squares can obtain accurate and steady outputs.

A PCB-embedded pressure sensor for wireless wind sail monitoring

A capacitive differential pressure sensor suitable to be implemented in a wireless sensor network has been designed, built, and experimentally tested. The pressure sensing unit is implemented in a printed circuit board (PCB) technology based on a thin 3D triple layers structure composed of: a pre-stressed polymeric diaphragm, woven glass reinforced epoxy resin (FR4) and metal layers. Aim of the developed sensor network is to sense the pressure field acting on the surface of a full battens sail by means of instrumented battens. Inside any instrumented batten an appropriate number of wireless nodes are mounted, the pressure sensing units is integrated in any wireless node, acting as pressure measurement spot. The sensor network is targeted to provide a real time differential pressure map over the sail surface. The pressure sensing unit behavior has been modeled using finite element simulations. By means of a static non-linear coupled mechanical-electrostatic model, has been possible to predict the pressure versus capacitance static characteristic and to tune the geometry of the transducer to reach the required resolution, sensitivity and time response in the appropriate full scale pressure input, ranging from ±250 Pascal.

Capacitive differential pressure sensor for harsh environments

A capacitive differential pressure sensor for the pressure range of 0–1 bar has been developed. The primary field of application is hydrodynamic flow measurements in hot petroleum wells. In these harsh environments the sensor has to survive high common mode pressure in the range of 1000 bar and temperatures up to 180°C. The pressure element is formed in a triple-stack of fusion-bonded silicon wafers. A bossed diaphragm etched in the upper wafer bends due to the differential pressure across it. The capacitance to the middle wafer is measured. A reference capacitor insensitive to the differential pressure enables compensation for capacitance shifts caused by ambient pressure and temperature changes. The lower silicon wafer is included to minimise the diaphragm stress from the package. An ASIC, certified for 230°C, which is developed at SINTEF, is used for signal read-out. The sensor is measured to have a low zero pressure signal drift, smaller than 2.5% of full-scale output, when the temperature is varied in the range 0–200°C and the ambient pressure in the range 0–1000 bar. The sensitivity of the sensor is sufficient for the application.

Dielectric-insensitive capacitive differential pressure gauge for use at low temperature

A capacitive differential pressure gauge for use at temperatures below 4 K is described. Fluid is admitted to two sample chambers with flexible walls to which a sensing capacitor is mechanically connected. Differential pressures between the chambers flex these walls and change the capacitance of the gauge. Because the capacitor is located outside these chambers, the gauge is insensitive to the dielectric variations of the fluid. Typical differential pressures of 105 Pa were measured with a common mode rejection ratio in excess of 50.

An IC-compatible polyimide pressure sensor with capacitive readout

A capacitive differential pressure sensor has been developed. The process used for the fabrication of the sensor is IC-compatible, meaning that the device potentially can be integrated on one chip with a suitable signal-conditioning circuit. A sensor for a differential pressure of ± 1 bar has been fabricated and tested with a frequency-modulated detection circuit, and good agreement is found with the theoretical model of the sensor. A nominal sensitivity Δ C/C of 17% has been measured for a positive differential pressure of 1 bar. The resolution of the complete detection system is 2.5 mbar (250 Pa).

A capacitive differential pressure sensor with polyimide diaphragm

A capacitive differential pressure sensor has been developed. The process used for the fabrication of the sensor is IC-compatible, meaning that the device can potentially be monolithically integrated on one chip with a suitable signal conditioning circuit. A sensor for a differential pressure range of was fabricated and tested with a frequency modulated detection circuit, and good agreement was found with the theoretical model of the sensor. A nominal sensitivity of 18% has been measured for a positive differential pressure of 1 bar.

Surface-micromachined capacitive differential pressure sensor with lithographically defined silicon diaphragm

A capacitive surface-micromachined sensor suitable for the measurement of liquid and gas pressures was fabricated. The structure consists of a polysilicon stationary electrode suspended 0.7 /spl mu/m above a 20-/spl mu/m-thick lightly doped silicon diaphragm formed by a patterned etch stop. The a priori patterning of the buried etch stop yields diaphragm widths independent of wafer thickness variations with excellent alignment. The design described here has a pressure range of 100 PSI, a nominal capacitance of 3.5 pF with a full scale span of 0.8 pF, and a temperature coefficient of 100 ppm/spl deg/C/sup -1/. Each device, including a matched reference capacitor, occupies 2.9 mm/sup 2/, yielding approximately 2000 devices per 100-mm wafer.

A thick-film capacitive differential pressure transducer

The development of a prototype capacitive pressure transducer and electronic interface is described. The device, constructed using thick films printed onto alumina, is designed to operate over the pressure range of 0-30 psi and may be used to measure either gauge or differential pressure. Practical measurements demonstrate high sensitivity and good linearity. A theoretical model of the device has been developed, which shows good correspondence with the measured results.