Differential Pressure Sensor Research Articles

HOPG/ZnO/HOPG pressure sensor

Pressure sensor is one of the most commonly used sensors in the research laboratories and industries. These are generally categorized in three different classes of absolute pressure sensors, gauge pressure sensors, and differential pressure sensors. In this paper, we fabricate and assess the pressure sensitivity of the current vs. voltage diagrams in a graphite/ZnO/graphite structure. Zinc oxide layers are deposited on highly oriented pyrolytic graphite (HOPG) substrates by sputtering a zinc target under oxygen plasma. The top electrode is also a slice of HOPG which is placed on the ZnO layer and connected to the outside electronic circuits. By recording the I-V characteristics of the device under different forces applied to the top HOPG electrode, the pressure sensitivity is demonstrated; at the optimum biasing voltage, the device current changes 10 times upon changing the pressure level on the top electrode by 20 times. Repeatability and reproducibility of the observed effect is studied on the same and different samples. All the materials used for the fabrication of this pressure sensor are biocompatible, the fabricated device is anticipated to find potential applications in biomedical engineering.

A Power-Efficient Readout for Wheatstone-Bridge Sensors With COTS Components

This paper presents a direct digital converter for Wheatstone bridge sensors, which is realized with commercial off-the-shelf components. The power efficiency of the readout is enhanced by embedding the bridge sensor in a second-order continuous-time sigma-delta modulator ( ${\mathrm{ CT}}\Delta \Sigma {\mathrm{ M}}$ ). By directly digitizing the output signal of a Wheatstone bridge in the current mode, the noise performance is dominated by the operational amplifier in the first integrator and the bridge sensor. To demonstrate the performance of the proposed circuit, an MEMS piezoresistive differential pressure sensor is used. Measurement results show that a resolution of 12.7 mPa $_{\mathrm {{rms}}}$ (0.41 $\text{m}\Omega _{\mathrm {{rms}}}$ ), with a 0.5-ms conversion time, can be achieved. Powered by 5 V, the circuit and the bridge sensor draw 9.55 and 7.58 mW, respectively.

Modeling and Simulation Research of the Self-gain Optical Fiber Differential Pressure Sensor Based on Damping Piston

This paper takes a modeling and simulation study on the self-gain optical fiber differential pressure sensor based on damping piston. Firstly, proposes the structure of mechanical packaging sensor probe based on the damping piston, and designs the sensor system; then, carries out the theoretical research on the sensor and builds the intensity modulation function and sensing model of the sensor. Simulation experiments based on the theoretical model are also conducted. The experimental results show that: changing the stiffness of the damping spring can change the detection range of the sensor. In certain stiffness of the damping spring, a sensor’s detected differential pressure DP is in good linearity with the sensor output value H, and the sensor has high sensitivity, whose output value can get self gain. The research shows that the optical fiber differential pressure sensor is of good detection performance and can meet the needs of different detection occasions.

High-Performance Low-Range Differential Pressure Sensors Formed With a Thin-Film Under Bulk Micromachining Technology

In the microelectromechanical systems (MEMS) field, low-range (e.g., kPa or sub-kPa) differential pressure sensors have remained difficult for decades. Generally, there are two unsolved problems that hinder volume production and wide applications in consumer-electronics. First, high sensitivity required very thin and large sensing diaphragm normally fabricated with low yield, and thus, high selling price. Second, high sensitivity required large deflection of the diaphragm easily causeing severe output of non-linearity that degrades the detecting precision. This paper reports a so-called thin-film under bulk (TUB) MEMS technique to high-yield fabricate high-performance low-range pressure sensors for smart central air-conditioning systems. With the single-wafer-based TUB structure, pressure-induced stress is highly concentrated in a bulk-silicon beam-island structure for piezoresistive readout, where a very thin but uniform poly-silicon diaphragm can be formed beneath the bulk-silicon structure to sustain the pressure. The beam-island reinforced structure brings about decreased deflection and highly linear output. Micro-columns are also formed under the bulk-silicon islands as over-range protection stoppers that are important for low-range pressure sensor. After the description about the 1.2 mm $\times 1.2$ mm tiny-sized sensor-chip design and its single-wafer fabrication process, a test is conducted that results in 22-mV output for 1.2-kPa measure range and very good linearity of ±0.05% (FS). About $100\times $ over-range protection capability of the sensor is also achieved. The novel high-yield TUB process can be used for low-cost production of high-performance pressure sensors for the applications of new-generation smart central air-conditional systems and spirometers, etc, and the bulk/surface combined TUB micromachining technique promises to be widely used for the formation of various complex MEMS structures. [2016-0309]

A preliminary investigation into the design of pressure cushions and their potential applications for forearm robotic orthoses

BackgroundLoad cells are often used in rehabilitation robotics to monitor human–robot interaction. While load cells are accurate and suitable for the stationary end-point robots used in rehabilitation hospitals, their cost and inability to conform to the shape of the body hinder their application in developing affordable and wearable robotic orthoses for assisting individuals in the activities of daily living. This exploratory work investigates the possibility of using an alternative technology, namely compliant polymeric air cushions, to measure interaction forces between the user and a wearable rigid structure.MethodsA polymeric air cushion was designed, analyzed using a finite element model (FEM), and tested using a bench-top characterization system. The cushions underwent repeatability testing, and signal delay testing from a step response while increasing the length of the cushion’s tubes. Subsequently, a 3D printed wrist brace prototype was integrated with six polymeric air cushions and tested in static conditions where a volunteer exerted isometric pronation/supination torque and forces in vertical and horizontal directions. The load measured by integrating data recorded by the six sensors was compared with force data measured by a high quality load cell and torque sensor.ResultsThe FEM and experimental data comparison was within the error bounds of the external differential pressure sensor used to monitor the pressure inside the cushion. The ratio obtained experimentally between the pressure inside the pressure cushion and the 8 N applied load deviated by only 1.28% from the FEM. A drift smaller than 1% was observed over 10 cycles. The rise times of the cushion under an 8 N step response for a 0.46, 1.03, and 2.02 m length tube was 0.45, 0.39, and 0.37 s. Tests with the wrist brace showed a moderate root mean square error (RMSE) between the force estimated by the pressure cushions and the external load cells. Specifically, the RMSE was 13 mNm, 500 mN, and 1.24 N for forearm pronation/supination torque, vertical force, and horizontal force, respectively.ConclusionsThe use of compliant pressure cushions was shown to be promising for monitoring interaction forces between the forearm and a rigid brace. This work lays the foundation for the future design of an array of pressure cushions for robotic orthoses. Future research should also investigate the compatibility of these polymeric cushions for data acquisition during functional magnetic resonance imaging in shielded rooms.

Differential capacitive pressure sensor design based on standard CMOS

A microelectromechanical system capacitive pressure sensor with a differential configuration (patent pending), including a reference and sensitive capacitor, is presented. A single cavity includes both reference and sensitive electrodes. This implementation is achieved by a size reduction of the sensitive electrode. A reduction of the 40% on the sensible electrode area represents a decrease in the sensor sensitivity of only 12.5%, and allows the reference capacitor implementation in the area commonly used only for the sensitive capacitor. A tridimensional model of the sensor was simulated using a finite-element solver considering coupled mechanical and electrostatic models. The simulations show that this pressure sensor has a sensitivity of 4.2 fF/bar. The proposed pressure sensor designs use only materials available in complementary metal oxide silicon (CMOS) standard processes. A CMOS compatible post-process, based on the sacrificial material technique and its restrictions is presented.

Study on Temperature and Synthetic Compensation of Piezo-Resistive Differential Pressure Sensors by Coupled Simulated Annealing and Simplex Optimized Kernel Extreme Learning Machine.

As a high performance-cost ratio solution for differential pressure measurement, piezo-resistive differential pressure sensors are widely used in engineering processes. However, their performance is severely affected by the environmental temperature and the static pressure applied to them. In order to modify the non-linear measuring characteristics of the piezo-resistive differential pressure sensor, compensation actions should synthetically consider these two aspects. Advantages such as nonlinear approximation capability, highly desirable generalization ability and computational efficiency make the kernel extreme learning machine (KELM) a practical approach for this critical task. Since the KELM model is intrinsically sensitive to the regularization parameter and the kernel parameter, a searching scheme combining the coupled simulated annealing (CSA) algorithm and the Nelder-Mead simplex algorithm is adopted to find an optimal KLEM parameter set. A calibration experiment at different working pressure levels was conducted within the temperature range to assess the proposed method. In comparison with other compensation models such as the back-propagation neural network (BP), radius basis neural network (RBF), particle swarm optimization optimized support vector machine (PSO-SVM), particle swarm optimization optimized least squares support vector machine (PSO-LSSVM) and extreme learning machine (ELM), the compensation results show that the presented compensation algorithm exhibits a more satisfactory performance with respect to temperature compensation and synthetic compensation problems.

차압식 유량계를 실장을 위한 Single Capacitive Type Differential 압력 센서 개발

차압식 유량계를 실장을 위한 Single Capacitive Type Differential 압력 센서 개발

Design of Novel FBG-Based Sensor of Differential Pressure with Magnetic Transfer.

In this paper, a differential pressure sensor with magnetic transfer is proposed, in which the non-electric measurement based on the fiber Bragg grating (FBG) with the position limiting mechanism is implemented without the direct contact of the sensing unit with the measuring fluid. The test shows that the designed sensor is effective for measuring differential pressure in the range of 0~10 kPa with a sensitivity of 0.0112 nm/kPa, which can be used in environments with high temperature, strong corrosion and high overload measurements.

Cryogenic instrumentation for ITER magnets

Accurate measurements of the helium flowrate and of the temperature of the ITER magnets is of fundamental importance to make sure that the magnets operate under well controlled and reliable conditions, and to allow suitable helium flow distribution in the magnets through the helium piping. Therefore, the temperature and flow rate measurements shall be reliable and accurate. In this paper, we present the thermometric chains as well as the venturi flow meters installed in the ITER magnets and their helium piping.The presented thermometric block design is based on the design developed by CERN for the LHC, which has been further optimized via thermal simulations carried out by CEA. The electronic part of the thermometric chain was entirely developed by the CEA and will be presented in detail: it is based on a lock-in measurement and small signal amplification, and also provides a web interface and software to an industrial PLC. This measuring device provides a reliable, accurate, electromagnetically immune, and fast (up to 100 Hz bandwidth) system for resistive temperature sensors between a few ohms to 100 kΩ.The flowmeters (venturi type) which make up part of the helium mass flow measurement chain have been completely designed, and manufacturing is on-going. The behaviour of the helium gas has been studied in detailed thanks to ANSYS CFX software in order to obtain the same differential pressure for all types of flowmeters. Measurement uncertainties have been estimated and the influence of input parameters has been studied. Mechanical calculations have been performed to guarantee the mechanical strength of the venturis required for pressure equipment operating in nuclear environment. In order to complete the helium mass flow measurement chain, different technologies of absolute and differential pressure sensors have been tested in an applied magnetic field to identify equipment compatible with the ITER environment.

Design of a 0-50 mbar pressure measurement channel compatible with the LHC tunnel radiation environment

The monitoring of cryogenic facilities often require the measurement of pressure in the sub 5’000 Pa range that are used for flow metering applications, for saturated superfluid helium, etc. The pressure measurement is based on the minute displacement of a sensing diaphragm often through contactless techniques by using capacitive or inductive methods. The LHC radiation environment forbid the use of standard commercial sensors because of the embedded electronics that are affected both by radiation induced drift and transient Single Event Effects (SEE). Passive pressure sensors from two manufacturers were investigated and a CERN designed radiation-tolerant electronics has been developed for measuring variable-reluctance sensors. During the last maintenance stop of the LHC accelerator, four absolute pressure sensors were installed in some of the low pressure bayonet heat exchangers and four differential pressure sensors on the venturi flowmeters that monitor the cooling flow of the 20.5 kA current leads of the ATLAS end-cap superconducting toroids. The pressure sensors operating range is about 1000 to 5000 Pa and the targeted uncertainty is +/- 50 Pa which would permit to measure the equivalent saturation temperature at 1.8 K within better than 0.01 K. This paper describes the radiation hard measuring head that is based on an inductive bridge, its associated radiation-tolerant electronics that is installed under the LHC superconducting magnets or the ATLAS detector cavern; and the first operational experience.

Torque Sensor Based on Differential Air Pressure Using Volumetric Strain

This paper proposes a torque sensor based on the differential air pressure measurement method using the volumetric strain of a mechanical sensing structure. A model of the measurement system based on the differential air pressure from the volumetric strain of the mechanical sensing structure is proposed and theoretically discussed. The error sources are identified and an error propagation model is presented for the proposed torque measurement method. Considering these error sources, a prototype torque sensor is presented as a case study for the method verification. Both the mechanical and readout electronics designs are discussed and analyzed. The mechanical sensitivity, resolution, and maximum stresses are analyzed using finite-element modeling. Based on the results from the simulation, a prototype torque sensor is manufactured and experimentally verified using a readout electronics design. For verification, the sensor prototype is measured under static torque to have a sensitivity of 0.04272V/ $\text{N}\cdot \text{m}$ and a range of ±117N $\cdot \text{m}$ . Compared with the nominal mechanical sensitivity result from the FEM simulation, this measured sensitivity has a difference less than 6%. The noise analysis of the designed readout electronics shows that the resolution of 0.006% can be achieved with this design. Furthermore, hysteresis analysis shows an error of 0.012% of full scale. From these results, it is also shown that the actual performance of the sensor is mainly limited by the differential pressure sensor and the readout electronics design and is not by the mechanical design of the sensor.

気圧センサによるUAVの姿勢推定のための高精度高度計測

In this paper, we developed a method of measuring altitude using a MEMS differential pressure sensor (DPS) with a cavity, for an unmanned aerial vehicle (UAV). The method includes modeling of DPS and prevention of the influence by the wind. Firstly, we built a transfer function model of the DPS and measured two parameters required for calculating altitude. The parameters were obtained with two experiments: applying static and dynamic pressure onto the both side of the DPS. Secondly, we developed on the basis of fluid dynamics a shielding cap which protects the sensor chip from direct wind caused by the propellers on a UAV, while keeping it to pursue the static pressure. The most sufficient cap, which is spherical with holes at a specific angle to the wind axis, removed both noise and the dynamic pressure.

MEMS差圧センサを搭載した羽ばたき機

MEMS差圧センサを搭載した羽ばたき機

Spatial variability of wind-induced air pressure fluctuations responsible for pressure pumping

Small air pressure fluctuations in the atmosphere are responsible for the pressure pumping effect, which leads to an enhancement of soil gas transport. To investigate the spatial variability of these air pressure fluctuations, several high-precision differential pressure sensors were installed at the floor of a Scots pine forest. The alignment of the pressure sensors allowed for the determination of the propagation direction and speed of the observed air pressure fluctuations. Below-canopy and above-canopy airflow characteristics were monitored to find possible links between the air pressure fluctuations and the airflow. Results show that the propagation direction of the air pressure fluctuations observed at the forest floor correspond to the above-canopy and not to the below-canopy wind direction. Moreover, propagation speed of the air pressure fluctuations is higher than the below-canopy wind speed and corresponds to above-canopy wind speed. These findings indicate a connection between below-canopy air pressure fluctuations and above-canopy airflow. The air pressure fluctuations were found to be well correlated up to a distance of 15 m. With increasing distance, the correlation strongly decreases. However, the calculated pressure pumping coefficient, which quantifies the strength of the pressure pumping effect, yields similar values up to a distance of 90 m. This allowed specifying the range of influence of the air pressure fluctuations.

Microprocessor system for collection meteoparameters based on Arduino platforms

The research the possibility of creating a compact universal module for collecting, processing and transmission of meteorological parameters of the atmosphere based on modern microprocessor systems and a set of corresponding sensors. Created model of a portable weather station conducted experimental research systems measure the speed and direction of air flow. It is shown, that the use of pressure sensors in the scheme of differential pressure gauge and a system of rotation allows for measuring the speed and direction of air flow in practical meteosystems.In future it is planned search for the optimal design of the tubes in the scheme of differential manometradlya specific pressure sensors. This will improve the sensitivity and enhance the ability of the practical use of such devices.

Sensor Calibration Design Based on D-Optimality Criterion

AbstractIn this study, a procedure for optimal selection of measurement points using the D-optimality criterion to find the best calibration curves of measurement sensors is proposed. The coefficients of calibration curve are evaluated by applying the classical Least Squares Method (LSM). As an example, the problem of optimal selection for standard pressure setters when calibrating a differential pressure sensor is solved. The values obtained from the D-optimum measurement points for calibration of the differential pressure sensor are compared with those from actual experiments. Comparison of the calibration errors corresponding to the D-optimal, A-optimal and Equidistant calibration curves is done.

Design and Implementation of Automatic Air Flow Rate Control System

Venturimeter is an apparatus that can be used to measure the air flow rate. In this experiment we designed a venturimeter which equipped with a valve that is used to control the air flow rate. The difference of pressure between the cross sections was measured with the differential pressure sensor GA 100-015WD which can calculate the difference of pressures from 0 to 3737.33 Pa. A 42M048C Z36 stepper motor was used to control the valve. The precision of this motor rotation is about 0.15 °. A Graphical User Interface (GUI) was developed to monitor and set the value of flow rate then an 8-bit microcontroller was used to process the control system In this experiment- the venturimeter has been examined to get the optimal parameter of controller. The results show that the controller can set the stable output air flow rate.

Silicon pressure transmitters with overload protection

The paper considers protection of silicon tensoresistive sensing elements against overload. A detailed analysis is focused on silicon crystal modeling of sensing elements exposed to pressures exceeding the upper limit of measurements. The existing designs of sensing element membranes and possible configurations of locking elements are summarized. In conclusion, the design of a sensing element in a differential pressure sensor with two locking elements is proposed.

A numerical model for pressure drop and flow distribution in a solar collector with U-connected absorber pipes

This study presents a numerical model calculating the pressure drop and flow distribution in a solar collector with U-type harp configuration in isothermal conditions. The flow maldistribution in the absorber pipes, caused by the different hydraulic resistances, was considered to evaluate the pressure drop across the collector. The model was developed in Matlab and is based on correlations found in literature for both friction losses and local losses, and was compared in terms of overall pressure drop against experimental measurements carried out on an Arcon Sunmark HT 35/10 solar collector at different flow rates and temperatures for water and water/propylene glycol mixture. For collector pressure drops higher than 1.4kPa, the relative difference between the model and measurements was within 5% for water and 7% for water/propylene glycol mixture. For lower pressure drops the relative difference increased, but remained within the accuracy of the differential pressure sensor. The flow distribution was mainly affected by the flow regime in the manifolds. Turbulent regime throughout the manifolds entailed a more uniform distribution across the absorber pipes compared to laminar regime. The comparison between calculated flow distributions and results from previous literature showed a good agreement.