Showing papers on "Pressure measurement published in 2011"

Pressure Sensor Based on the Fiber-Optic Extrinsic Fabry-Perot Interferometer

Abstract: Pressure sensors based on fiber-optic extrinsic Fabry-Perot interferometer (EFPI) have been extensively applied in various industrial and biomedical fields. In this paper, some key improvements of EFPI-based pressure sensors such as the controlled thermal bonding technique, diaphragm-based EFPI sensors, and white light interference technology have been reviewed. Recent progress on signal demodulation method and applications of EFPI-based pressure sensors has been introduced. Signal demodulation algorithms based on the cross correlation and mean square error (MSE) estimation have been proposed for retrieving the cavity length of EFPI. Absolute measurement with a resolution of 0.08 nm over large dynamic range has been carried out. For downhole monitoring, an EFPI and a fiber Bragg grating (FBG) cascade multiplexing fiber-optic sensor system has been developed, which can operate in temperature 300 °C with a good long-term stability and extremely low temperature cross-sensitivity. Diaphragm-based EFPI pressure sensors have been successfully used for low pressure and acoustic wave detection. Experimental results show that a sensitivity of 31 mV/Pa in the frequency range of 100 Hz to 12.7 kHz for aeroacoustic wave detection has been obtained.

Experimental Measurements of Ingestion Through Turbine Rim Seals—Part I: Externally Induced Ingress

Abstract: This paper describes a new research facility which experimentally models hot gas ingestion into the wheel-space of an axial turbine stage. Measurements of CO2 gas concentration in the rim-seal region and inside the cavity are used to assess the performance of two generic (though engine-representative) rim-seal geometries in terms of the variation of concentration effectiveness with sealing flow rate. The variation of pressure in the turbine annulus, which governs this externally-induced (EI) ingestion, was obtained from steady pressure measurements downstream of the vanes and near the rim seal upstream of the rotating blades. Although the ingestion through the rim seal is a consequence of an unsteady, three-dimensional flow field and the cause-effect relationship between pressure and the sealing effectiveness is complex, the experimental data is shown to be successfully calculated by simple effectiveness equations developed from a previously published orifice model. The data illustrate that, for similar turbine-stage velocity triangles, the effectiveness can be correlated using a non-dimensional sealing parameter, Φo . In principle, and within the limits of dimensional similitude, these correlations should apply to a geometrically-similar engine at the same operating conditions. Part 2 of this paper describes an experimental investigation of rotationally-induced (RI) ingress, where there is no mainsteam flow and consequently no circumferential variation of external pressure.Copyright © 2011 by ASME

High speed PIV applied to aerodynamic noise investigation

Abstract: In this paper, we study the acoustic emissions of the flow over a rectangular cavity. Especially, we investigate the possibility of estimating the acoustic emission by analysis of PIV data. Such a possibility is appealing, since it would allow to directly relate the flow behavior to the aerodynamic noise production. This will help considerably in understanding the noise production mechanisms and to investigate the possible ways of reducing it. In this study, we consider an open cavity with an aspect ratio between its length and depth of 2 at a Reynolds number of 2.4 9 104 and 3.0 9 104 based on the cavity length. The study is carried out combining high speed two-dimensional PIV, wall pressure measurements and sound measurements. The pressure field is computed from the PIV data. Curle’s analogy is applied to obtain the acoustic pressure field. The pressure measurements on the wall of the cavity and the sound measurements are then used to validate the results obtained from PIV and check the range of validity of this approach. This study demonstrated that the technique is able to quantify the acoustic emissions from the cavity and is promising especially for capturing the tonal components on the sound emission.

In-Line Pipe Device Checking by Short-Period Analysis of Transient Tests

Abstract: In this paper, the results of laboratory transient tests concerning the interaction between a pressure wave and an in-line device are discussed. Transients are generated by means of a fast and complete closing of an end valve, and pressure measurements are carried out just upstream of the maneuver valve. The main effect of the device on the pressure time-history—hereafter referred to as pressure signal—is a sharp increase caused by the pressure wave reflection. Three experimental setups are considered, in which different in-line devices are installed (i.e., a ball valve, a butterfly valve, and different-sized orifices). The pressure signal is analyzed in the time domain, and a reliable evaluation of the device location is obtained by means of wavelet functions. Furthermore, on the basis of the value of the pressure increase, the status of the device can be determined; experimental results are synthesized in a dimensionless diagram. Finally, criteria for using the obtained results in other pipe systems are...

Comparison of three types of tongue pressure measurement devices.

Abstract: A new tongue pressure device consisting of a simple and safe disposable probe and manometer has been developed. This report describes a study that examined the validity of the new device, comparing it to a widely used tongue pressure manometer, the Iowa Oral Performance Instrument (IOPI), and to the stable adhered three air-filled bulbs manometry system. The first test compared maximum tongue pressure measured with the new device and the IOPI (13 male, 9 female, 25.0 years). The second test compared maximum tongue pressure and swallowing tongue pressure measured with the new device and the three-bulb device (13 male, 9 female, 31.0 years). Significant correlations of maximum tongue pressure were found between the new device and the IOPI in the first test (p < 0.05). In the second test, significant correlations of maximum tongue pressure were found between the new device at the anterior and middle sensors (p < 0.05) but not at the posterior sensor of the three-bulb device. Significant correlations of swallowing tongue pressure between the new device and the three-bulb device were found (p < 0.05). These findings demonstrate that the measurements by the new simple tongue pressure device are closely equivalent to those of the IOPI and three-bulb devices, demonstrating that the new device is capable of accurately measuring the pressure generated by the whole tongue.

Automatic noninvasive measurement of arterial blood pressure

Abstract: This paper discussed arterial blood pressure measurement. Because of the high rate of hypertension in the adult population and its harmful effects, the measurement of arterial blood pressure is of great clinical significance. Manual sphygmomanometry, developed more than a hundred years ago, is currently the most accurate non-invasive technique for arterial blood pressure measurement. Since manual sphygmomanometry requires a well-trained examiner, only single measurements of blood pressure will generally be performed by a physician during a given visit. This single measurement only provides partial information since blood pressure changes spontaneously. The available automatic blood pressure meters, mainly based on oscillometry, can be used at home but some of them are of low accuracy. A direct technique for the measurement of systolic blood pressure by means of the detection of the blood pressure pulses' reappearance during cuff deflation has the potential to provide accurate automatic measurement of systolic blood pressure.

Device and method for measuring arterial blood pressures based on pulse wave signals and electrocardiosignals

Abstract: The invention relates to a device and method for measuring arterial blood pressures based on pulse wave signals and electrocardiosignals, wherein the device comprises a microprocessor, a pulse wave signal measuring unit, an electrocardiosignal measuring unit, a communication module, a data storage module and an LCD (liquid crystal display) module, and the microprocessor is respectively connected with the pulse wave signal measuring unit, the electrocardiosignal measuring unit, the communication module, the data storage module and the LCD module by control lines. The device provided by the invention is small in size, therefore, the device is suitable to be worn for non-intrusively and continuously detecting and recording the blood pressure values for a long time. Compared with the existingblood pressure measurement techniques, the device and method provided by the invention have the advantages that in the process of blood pressure measurement, the dependence on an inflated cuff is ridded; and meanwhile, the blood pressure calculation method applied to the device is small in computation load, and can be implemented by the microprocessor with a limited computational capability, therefore, the device is low in cost and easy to use.

Demonstration of an All-Sapphire Fabry–Pérot Cavity for Pressure Sensing

Abstract: This letter presents a first demonstration of a monolithic sapphire Fabry-Perot (FP) cavity for pressure sensing. The prototype was constructed by combining reactive ion etching with direct wafer bonding. Long-term testing proves that the adhesive-free wafer bond is sufficient to create a sealed FP cavity as a pressure transducer. Pressure measurement over a range of 0.04-1.38 MPa has been demonstrated at room temperature using white-light interferometry. With an all-sapphire configuration, the prototype reported here can be further developed into a pressure sensor with high-temperature harsh-environment capability.

Comparison of air-charged and water-filled urodynamic pressure measurement catheters.

Abstract: Aims Catheter systems are utilized to measure pressure for diagnosis of voiding dysfunction. In a clinical setting, patient movement and urodynamic pumps introduce hydrostatic and motion artifacts into measurements. Therefore, complete characterization of a catheter system includes its response to artifacts as well its frequency response. The objective of this study was to compare the response of two disposable clinical catheter systems: water-filled and air-charged, to controlled pressure signals to assess their similarities and differences in pressure transduction. Methods We characterized frequency response using a transient step test, which exposed the catheters to a sudden change in pressure; and a sinusoidal frequency sweep test, which exposed the catheters to a sinusoidal pressure wave from 1 to 30 Hz. The response of the catheters to motion artifacts was tested using a vortex and the response to hydrostatic pressure changes was tested by moving the catheter tips to calibrated heights. Results Water-filled catheters acted as an underdamped system, resonating at 10.13 ± 1.03 Hz and attenuating signals at frequencies higher than 19 Hz. They demonstrated significant motion and hydrostatic artifacts. Air-charged catheters acted as an overdamped system and attenuated signals at frequencies higher than 3.02 ± 0.13 Hz. They demonstrated significantly less motion and hydrostatic artifacts than water-filled catheters. The transient step and frequency sweep tests gave comparable results. Conclusions Air-charged and water-filled catheters respond to pressure changes in dramatically different ways. Knowledge of the characteristics of the pressure-measuring system is essential to finding the best match for a specific application. Neurourol. Urodynam. 30:329–334, 2011. © 2011 Wiley-Liss, Inc.

Thermal transpiration flow: A circular cross-section microtube submitted to a temperature gradient

Abstract: Thermal transpiration is the macroscopic movement of rarefied gas molecules induced by a temperature gradient. The gas moves from the lower to the higher temperature zone. An original method is proposed here to measure the mean macroscopic movement of gas in the case of a long circular cross-section glass microtube onto which a gradient of temperature is applied. The mass flow rate and the thermomolecular pressure difference have been measured by monitoring the absolute pressure evolution in time at both ends of the capillary using high-speed response pressure gauges. Two gases, nitrogen and helium, are studied and three different temperature differences of 50, 60, and 70 °C are applied to the tube. The analyzed gas rarefaction conditions vary from transitional to slip regime.

Recovering the Water-Wave Profile from Pressure Measurements

Abstract: A new method is proposed to recover the water-wave surface elevation from pressure data obtained at the bottom of the fluid. The new method requires the numerical solution of a nonlocal nonlinear equation relating the pressure and the surface elevation which is obtained from the Euler formulation of the water-wave problem without approximation. From this new equation, a variety of different asymptotic formulas are derived. The nonlocal equation and the asymptotic formulas are compared with both numerical data and physical experiments. The solvability properties of the nonlocal equation are rigorously analyzed using the Implicit Function Theorem.

High-Sensitivity Inductive Pressure Sensor

Abstract: A new type of pressure sensors with extremely high sensitivity is introduced. Unlike piezoresistive, capacitive, and linear-variable-differential-transformer-based pressure sensors, the new sensor is based on a technique for substantially changing the inductance of a coil. The prototype device has demonstrated a change in inductance of approximately 34.5 mH over a pressure range of 10 kPa. The sensor offers a number of desirable features, including linearity, low temperature, and pressure hysteresis, in addition to small size.

Novel fabric pressure sensors: design, fabrication, and characterization

Abstract: Soft and pliable pressure sensors are essential elements in wearable electronics which have wide applications in modern daily lives. This paper presents a family of fabric pressure sensors made by sandwiching a piece of resistive fabric strain sensing element between two tooth-structured layers of soft elastomers. The pressure sensors are capable of measuring pressure from 0 to 2000?kPa, covering the whole range of human?machine interactions. A?pressure sensitivity of up to 2.98 ? 10 ? 3?kPa ? 1 was obtained. Theoretical modeling was conducted based on an energy method to predict the load?displacement relationship for various sensor configurations. By adjusting the Young's modulus of the two conversion layers, as well as the geometrical dimensions, the measurement ranges, and sensitivities of the sensors can be quantitatively determined. The sensors are being used for pressure measurements between the human body and garments, shoes, beds, and chairs.

Application of fast-responding pressure-sensitive paint to a hemispherical dome in unsteady transonic flow

Abstract: The current work focuses on the development and application of fast-responding polymer/ceramic pressure-sensitive paint (PSP) as an advanced surface pressure measurement technique for unsteady flow fields in large-scale wind tunnels. To demonstrate the unsteady PSP technique, the unsteady surface pressure distribution over a hemispherical dome placed in the United States Air Force Research Laboratory’s Trisonic Gasdynamics Facility (TGF) was studied by phase-locking to the characteristic frequency in the flow caused by an unsteady separated shear layer shed from the dome. The wind tunnel was operated at stagnation pressures of 23.92 and 71.84 kPa, with the test section flow at Mach 0.6. Under the two operating conditions, the predominant shear layer frequency was measured to be 272 and 400 Hz, respectively. The quasi-periodic shear layer frequency enabled a phase-averaged method to be employed for capturing the unsteady shock motion on the hemisphere. Unsteady pressure data resulting from this technique are shown to correlate well with measurements acquired by conventional measurement techniques. Measurement uncertainty in the phase-averaging technique will be discussed. To address measurement uncertainties from temperature sensitivity and model movement, a new implementation of an AC-coupled data representation is offered.

Optofluidic membrane interferometer: An imaging method for measuring microfluidic pressure and flow rate simultaneously on a chip

Abstract: We present a novel image-based method to measure the on-chip microfluidic pressure and flow rate simultaneously by using the integrated optofluidic membrane interferometers (OMIs). The device was constructed with two layers of structured polydimethylsiloxane (PDMS) on a glass substrate by multilayer soft lithography. The OMI consists of a flexible air-gap optical cavity which upon illumination by monochromatic light generates interference patterns that depends on the pressure. These interference patterns were captured with a microscope and analyzed by computer based on a pattern recognition algorithm. Compared with the previous techniques for pressure sensing, this method offers several advantages including low cost, simple fabrication, large dynamic range, and high sensitivity. For pressure sensing, we demonstrate a dynamic range of 0-10 psi with an accuracy of ±2% of full scale. Since multiple OMIs can be integrated into a single chip for detecting pressures at multiple locations simultaneously, we also demonstrated a microfluidic flow sensing by measuring the differential pressure along a channel. Thanks to the simple fabrication that is compatible with normal microfluidics, such OMIs can be easily integrated into other microfluidic systems for in situ fluid monitoring.

Leakage location in water distribution networks based on correlation measurement of pressure sensors

Abstract: Leaks are present to some extent in all water-distribution systems. This paper proposes a leakage localisation method based on the pressure measurements and pressure sensitivity analysis of nodes in a water distribution network. The sensitivity analysis using analytical tools is not a trivial job in a real network because of the huge non-explicit, non-linear systems of equations that describe its dynamics. Simulations of the network in presence and absence of leakage may provide an approximation of this sensitivity. A fault isolation algorithm which correlates on line the residuals (generated by comparing the available pressure measurements with their estimation using a model) with the fault sensitivity matrix is used. The proposed algorithm has been applied in simulation to a DMA (District Metered Area) in the Barcelona Network using EPANET software. The results obtained were promising

Side-Hole Photonic Crystal Fiber With Ultrahigh Polarimetric Pressure Sensitivity

Abstract: We propose a side-hole polarization-maintaining photonic crystal fiber (PM-PCF) with ultrahigh polarimetric sensitivity to hydrostatic pressure. The proposed fiber has a very simple structure with a core surrounded by a double row of large air holes and a central row of small air holes. A pair of ultralarge side holes was symmetrically introduced into the silica cladding of the fiber to enhance the polarimetric response to hydrostatic pressure. Modal birefringence B as large as 2.34 × 10-3 and polarimetric pressure sensitivity dB/dp as high as -2.30 × 10-5 MPa-1 were achieved at 1.55 μm for the proposed fiber. Combining the advantages of both side-hole fibers and PM-PCFs, it is believed to be an excellent candidate for future applications of hydrostatic pressure measurement.

Readout methods for an inductively coupled resonance sensor used in pressure garment application

Abstract: The methods needed to inductively read a passive resonance sensor in pressure measurement are studied. A simple dual-layer pressure sensor, a small portable phase response measurement unit and the methods to extract a coupling coefficient compensated resonance frequency are presented. The functionality and accuracy of the measurement are tested in a test rig and demonstrated in a realistic measurement environment. According to the test measurements, the overall performance of this wireless system is promising and the accuracy is within the typical range of the measurements made in the field of pressure garments.

Online monitoring and analysis of resin pressure inside composite laminate during zero‐bleeding autoclave process

Abstract: Resin pressure is one of the most important parameters in manufacturing composites during autoclave process. It not only greatly influences resin flow behavior, but also has effects on void formation and elimination. Online monitoring resin pressure can provide an important guidance for the optimization of the processing parameters and the control of the quality of composites. In this study, a resin pressure online measuring system for autoclave process was established based on the principle of pressure transfer in liquid, and the size of the measuring probe of the system was optimized to increase the accuracy of measured resin pressure. The results indicate that the accuracy and the dynamic response of the system can meet the requirements of resin pressure measurement during autoclave process. Furthermore, by means of this proposed resin pressure measuring system and the measurements of compaction properties of the fabric stacks, the resin pressures inside carbon fiber fabric/epoxy resin and glass fiber fabric/epoxy resin prepreg stacks during autoclave process were investigated, especially for the zero-bleeding process which is prevailing for aircraft composite structures. It is demonstrated that during zero-bleeding process, the resin pressures, which conform to the spring and piston model, uniformly distribute along through-thickness and in-plane directions. In addition, the resin pressure profile is significantly influenced by the fiber volume fraction of the prepregs, indicating that fiber content of prepreg should be optimized for achieving free defects and uniform fiber distribution. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers

Multiplexed pressure sensing with elastomer membranes

Abstract: We demonstrate a novel optical pressure measurement platform for microfluidics. The pressure sensors operate as pneumatically-tunable microlenses whose focal lengths vary with pressure. We show that pneumatic lens arrays can be used to perform sensitive multiplexed pressure measurements in microfluidic channels.

Integrated micro Pirani gauge based hermetical package monitoring for uncooled VO x bolometer FPAs

Abstract: This paper presents the design and fabrication of a micro Pirani gauge using VO x as the sensitive material for monitoring the pressure inside a hermetical package for micro bolometer focal plane arrays (FPAs). The designed Pirani gauge working in heat dissipating mode was intentionally fabricated using standard MEMS processing which is highly compatible with the FPAs fabrication. The functional layer of the micro Pirani gauge is a VO x thin film designed as a 100 × 200 μm pixel, suspended 2 μm above the substrate. By modeling of rarefied gas heat conduction using the Extended Fourier’s law, finite element analysis is used to investigate the sensitivity of the pressure gauge. Also the thermal interactions between the micro Pirani gauge and bolometer FPAs are verified. From the fabricated prototype, the measured device TCR is about −0.8% K−1 and the sensitivity about 1.84 × 10−3 W K−1 mbar−1.

A Capillary Tube Viscometer Designed for Measurements of Hydrogen Gas Viscosity at High Pressure and High Temperature

Abstract: A capillary tube viscometer was developed to measure the dynamic viscosity of gases for high pressure and high temperature. The apparatus is simple and designed for safe-handling operation. The gas was supplied to the capillary tube from a high-pressure reservoir tank through a pressure regulator unit to maintain a steady state flow. The measurements of a pressure drop across the capillary tube with high accuracy under extreme conditions are the main challenge for this method. A differential pressure sensor for high pressures up to 100 MPa is not available commercially. Therefore, a pair of accurate absolute pressure transducers was used as a differential pressure sensor. Then the pressure drop was calculated by subtracting the outlet pressure from the inlet one with a resolution of 100 Pa at 100 MPa. The accuracy of the present measurement system is confirmed by measuring the viscosity of nitrogen as a reference gas. The apparatus provided viscosities of nitrogen from ambient temperature to 500 K and hydrogen from ambient temperature to 400 K and for pressures up to 100 MPa with a maximum deviation of 2.2 % compared with a correlation developed by the present authors and with REFPROP (NIST).

Studies of a high-sensitive surface acoustic wave sensor for passive wireless blood pressure measurement

Abstract: This paper develops a novel, high-sensitive surface acoustic wave (SAW) blood pressure sensor based on a 434.5 MHz resonator fabricated on an ST-cut quartz beam. First, 50 types of resonators with different layouts were designed, and then the sensitivity of the pressure sensors with different structures and sizes was simulated and calculated by using COMSOL Multiphysics software. Finally, a resonator with good performance was selected to fabricate a set of blood pressure sensors in different sizes, and these sensors were tested and evaluated through the use of both static and dynamic pressure measurements as well as animal experiments. For the sensor with a beam size of 10 mm × 1.3 mm × 0.3 mm, the results showed that in the range of 0–300 mmHg the pressure sensitivity was about 1.9 kHz/mmHg with good linearity, which matched well with the simulation results, additionally, the maximum non-linear curve fitting error was found to be less than ±1 mmHg. Moreover, it could detect a pressure change as small as 0.1 mmHg. This sensor can be used to monitor blood pressure passively and wirelessly, and it will hopefully be applied in implantable devices for body pressure measurements in further research.

Does femoral venous pressure measurement correlate well with intrabladder pressure measurement? A multicenter observational trial.

Abstract: Purpose To investigate if femoral venous pressure (FVP) measurement can be used as a surrogate measure for intra-abdominal pressure (IAP) via the bladder.

A Monolithic Piezoresistive Pressure-Flow Sensor With Integrated Signal-Conditioning Circuit

Abstract: A monolithic integrated pressure-flow sensor with on-chip signal-conditioning CMOS circuit has been developed for simultaneous measurements of pressure and flow rates, which is used in automatic control system. Both the pressure sensing and flow sensing are based on the piezoresistive effect, and only one additional mask is applied on the integrated pressure sensor to realize the pressure-flow sensor. A fully integrated pressure-flow sensor, which is based on inter-COMS process, is fabricated and packaged. A commercial computational fluid dynamics (CFD) software package, Fluent 6.1, is used to model the flow inside this pressure-flow sensor. The performance of the sensor is then predicted utilizing Coventorware based on the result from CFD simulation. For the testing, pressure sensor was first calibrated at the range of 0-50 KPa, and it showed a pressure sensitivity of 1.3 mV/mmHg. Afterwards, the simultaneous measurement of pressure and flow rate is implemented at air flow rates of 0-5 L/min. Both the pressure output and flow output have a quadratic relation with the input flow rate of the fluid, which is consistent with the simulation results. Based on the pressure calibration, the dependence of pressure to flow rate is finally obtained.