Showing papers on "Pressure measurement published in 2005"

A wireless microsystem for the remote sensing of pressure, temperature, and relative humidity

Abstract: This work presents a microsystem that utilizes inductive power and data transfer through a backscatter-modulated carrier and a transducer interface that monitors its environment through embedded capacitive transducers. Formed on a single chip, transducers for temperature, pressure, and relative humidity are realized using a silicon-on-glass process that combines anodic bonding and a silicon-gold eutectic to realize vacuum-sealed cavities with low-impedance (6 /spl Omega/) electrical feedthroughs. Temperature is sensed capacitively using a row of Si/Au bimorph beams that produce a sensitivity of 15 fF//spl deg/C from 20 to 100/spl deg/C. The absolute pressure sensors have a sensitivity of 15 fF/torr and a range from 500 to 1200 torr, while the relative humidity sensor responds with 39 fF/%RH from 20 to 95%RH. A relaxation oscillator implements low-power capacitance-to-frequency conversion on a second chip with a sensitivity of 750 Hz/pF at 10 kHz, forming a 341 /spl mu/W transducer interface. The system is remotely powered by a 3-MHz carrier and has a volume of 32 mm/sup 3/, including the hybrid antenna wound around the perimeter of the system.

Miniature fiber-optic pressure sensor

Abstract: This letter presents a miniature fiber-optic pressure sensor fabricated directly on the tip of a fiber. The sensor measures only 125 /spl mu/m in diameter. A Fabry-Pe/spl acute/rot cavity and a thin silica diaphragm are fabricated by simple techniques involving only fusion splicing, cleaving, and wet chemical etching. Interference pattern of the sensor is analyzed and issues in sensor design are discussed. The sensor has been tested for static pressure response, showing excellent repeatability and no hysteresis. Its all-fused-silica structure lends it great potential for high-temperature pressure measurements. Pressure testing results at 530/spl deg/C are given. The sensor may also find uses in medical applications.

Standing Wave Difference Method for Leak Detection in Pipeline Systems

Abstract: The current paper focuses on leakage detection in pipe systems by means of the standing wave difference method (SWDM) used for cable fault location in electrical engineering. This method is based on the generation of a steady-oscillatory flow in a pipe system, by the sinusoidal maneuver of a valve, and the analysis of the frequency response of the system for a certain range of oscillatory frequencies. The SWDM is applied to several configurations of pipe systems with different leak locations and sizes. A leak creates a resonance effect in the pressure signal with a secondary superimposed standing wave. The pressure measurement and the spectral analysis of the maximum pressure amplitude at the excitation site enable the identification of the leak frequencies and, consequently, the estimation of the leak approximate location. Practical difficulties of implementation of this technique in real life systems are discussed.

Miniature all-silica fiber optic pressure and acoustic sensors

Abstract: We present a miniature diaphragm-based Fabry-Perot (F-P) interferometric fiber optic sensor fabricated by novel techniques for pressure or acoustic wave measurement that is only approximately 032 mm in diameter By choosing different diaphragm thicknesses and effective diameters, we obtain a sensor measurement range from 5 to 10,000 psi (1 psi = 5172 Torr) and a frequency response up to 2 MHz In addition, the sensor's F-P cavity can be set from micrometers to millimeters with a precision of several nanometers With the all-silica structure, the sensor is reliable, biocompatible, and immune to electromagnetic interference and has high-temperature sensing capability

Accuracy in the Measurement of Compartment Pressures: A Comparison of Three Commonly Used Devices

Abstract: Background: In situations in which accurate physical diagnosis is inconclusive, an objective method for measuring compartment pressure can aid in the diagnosis of compartment syndrome. Previous studies have compared measurement devices with each other but not with an accurately determined gold standard. The purpose of the present study was to devise a reproducible in vitro model of compartment pressure and to compare commonly used measurement devices in order to determine their accuracy. Methods: With a graduated cylinder being used to generate a known pressure, freshly harvested ovine muscle was placed into a chamber for testing. The cylinder was incrementally filled with saline solution (in fifty-five steps), and measurements of tissue pressure were obtained with use of the Stryker Intracompartmental Pressure Monitor System, an arterial line manometer, and the Whitesides apparatus. Each device was tested with a straight needle, a side-port needle, and a slit catheter, for a total of nine setups in all. Five trials were done with each setup. Control pressures were calculated on the basis of the height of the saline solution column (test range, 0.13 to 10.80 kPa). Multiple regression analysis was used to compare measured tissue pressures with calculated control pressures. Results: Most methods demonstrated excellent correlation (R2 > 0.95) between calculated and measured pressures. The arterial line manometer with the slit catheter showed the best correlation (R2 = 0.9978), and the Whitesides apparatus with the side-port needle showed the worst (R2 = 0.9115). Furthermore, the Stryker system with the side-port needle demonstrated the least constant bias (+0.06 kPa). Straight needles tended to overestimate pressure. Two of the three needle configurations involving the Whitesides apparatus overestimated pressure. The data for the Whitesides methods had the highest standard errors, showing clinically unacceptable scatter. Conclusion: Side-port needles and slit catheters are more accurate than straight needles are. The arterial line manometer is the most accurate device. The Stryker device is also very accurate. The Whitesides manometer apparatus lacks the precision needed for clinical use. Clinical Relevance: When physical examination findings are inconclusive, accurate measurement of compartment pressures can aid in timely management and can minimize patient morbidity. Measurement should be done with use of the most accurate technique available.

Blood pressure variability: its measurement and significance in hypertension.

Abstract: The occurrence of blood pressure fluctuations over time has been documented since the 18th century, but the clinical importance of this phenomenon is only now being recognized. The introduction of ambulatory blood pressure monitoring in the late 1960s represented a major step forward in the study of blood pressure behaviour and helped to characterize the relationship between blood pressure variability and cardiovascular disease. In hypertension, blood pressure variability increases with increasing blood pressure and correlates closely with target-organ damage, independently of absolute blood pressure values. This has important consequences for treatment, which in the past has focused on reducing mean blood pressure values as the main goal. Experimental evidence suggests that drugs capable of buffering or reducing blood pressure variability may confer additional benefits on target-organ protection. Effective target-organ protection could best be afforded by antihypertensive agents that provide efficient 24-h blood pressure control and also stabilize blood pressure variability. Mathematical indices, such as the trough:peak ratio and the smoothness index, provide useful measures of the homogeneity of the antihypertensive effect over 24 h; optimum control is provided by drugs with a trough:peak ratio close to 1 and a smoothness index > 1, as is observed with long-acting drugs such as telmisartan or amlodipine. Recently, a direct relationship was demonstrated between homogeneous blood pressure control and treatment-induced regression of left ventricular hypertrophy, emphasizing the importance of smooth 24-h blood pressure control. In conclusion, the goals of antihypertensive treatment should consider the reduction of both 24-h mean blood pressure and its variability. Long-lasting drugs or drug combinations are preferable to ensure a homogeneous and smooth 24-h blood pressure profile.

A comparison of noninvasive MRI-based methods of estimating pulmonary artery pressure in pulmonary hypertension.

Abstract: Purpose To assess the accuracy of several noninvasive MRI-based estimators of pulmonary artery pressure by comparing them with invasive pressure measurement. Materials and Methods We compared five MRI methods with invasive pressure measurement by catheterization, in one group of pulmonary hypertension (PH) patients. Doppler echocardiography was included as a reference method. Main inclusion criterion was a mean pulmonary artery pressure above 25 mmHg at catheterization. MRI velocity quantification was used to obtain pulmonary flow acceleration and ejection times, and pulse wave velocity. The ventricular mass index was also assessed on MRI. Two commercially available 1.5-T systems were used for this study. Results Data from 44 patients were analyzed. Correlation of acceleration time with mean pressure was: r = –0.21, P = 0.21, correlation of the acceleration/ejection time ratio with systolic pressure was: r = –0.26, P = 0.01. The ventricular mass index showed the best correlation with mean pressure, with r = 0.56, P < 0.001. Using the pulse wave velocity and the cross-sectional area of the pulmonary artery, the mean pressure could not be estimated accurately. Conclusion Accurate estimation of pulmonary artery pressure in PH patients was not feasible by the MRI estimators studied. These noninvasive methods cannot replace right heart catheterization at this moment. J. Magn. Reson. Imaging 2005;22:67–72. © 2005 Wiley-Liss, Inc.

Velocity and surface pressure measurements in an open cavity

Abstract: Subsonic flow of approximately Mach 0.2 over cavities with L/D ratios of 5.16 and 1.49 were studied experimentally using particle image velocimetry (PIV), surface pressure measurements, and hot-wire measurements. The incoming boundary layer was turbulent in both cases. The PIV data was analyzed to yield mean flow characteristics, vorticity field information, and two-point statistics for the velocity field. The hot-wire data was combined with surface pressure measurements to detail the correlations between velocity and pressure fluctuations. An analysis of the correlation between surface pressure measurements shows contrasting characteristics for the two cavity aspect ratios. The PIV data was combined with surface pressure measurements through the application of quadratic stochastic estimation to predict the time-dependent behavior of the velocity field. An examination of the results supports the existence of different cavity flow modes, as has been suggested in much of the literature.

Application of pressure-sensitive paint for determination of the pressure field and calculation of the forces and moments of models in a wind tunnel

Abstract: The visualization and measurements of aerodynamic effects on a 3D aircraft model were conducted using an optical pressure measurement system, based on the pressure-sensitive paint (PSP) technique. PSP technology provides a good understanding of the flow around the wind tunnel model. The PSP technique can be used to carry out absolute pressure measurements on a surface of the model and to determine additional aerodynamic data using scientific-grade cameras and image processing techniques. Surface pressures from the top, bottom, left, and right viewing directions were obtained using the DLR-PSP system on the entire surface, which can be observed by eight CCD cameras. Finally, the measured pressures can be integrated to calculate the forces and moments of the complete model, or parts thereof.

Image measurements of unsteady pressure fluctuation by a pressure-sensitive coating on porous anodized aluminium

Abstract: Pressure-sensitive luminescent coating on porous anodized aluminium (AA-PSP) was applied to measure non-periodic unsteady pressure distribution on a wind-tunnel model. A high-speed digital video camera was used to capture the PSP signal. The pressure-sensitive dye was tris(4,7-diphenylphenanthroline) ruthenium(II) ([Ru(dpp)3]2+). The coating has a short response time of O(10 µs), although it exhibits temperature and humidity sensitivities. A hydrophobic coating was applied on the anodized aluminium surface to suppress the humidity sensitivity. A temperature sensitive paint was used to obtain the temperature distribution instantaneously with the pressure. The temperature data were used to correct the PSP response. An appropriate data acquisition procedure as well as digital image processing algorithm was established to compensate for the error from the temperature and humidity sensitivities. The present system was applied to measure the pressure distribution on a delta wing at a high angle of attack in transonic flow, whose flow is unsteady due to the interaction between shock waves and leading edge vortices. The non-periodic unsteady pressure distribution on the delta wing was successfully measured with the sampling rate of 1 kHz and within a few per cent error in absolute pressure level.

In vivo pressure estimation using subharmonic contrast microbubble signals: proof of concept

Abstract: Changes in ambient pressure affects the reflectivity of ultrasound contrast microbubbles leading to an excellent correlation between subharmonic signals and hydrostatic pressure. The aortas of two dogs were scanned with an experiment pulse-echo system to validate in vivo pressure estimation based on subharmonic microbubble signals. Results matched well with instantaneous pressure measurements (from 20-60 mmHg) obtained simultaneously with a pressure catheter (root mean square errors <27%).

A microfluidic experimental platform with internal pressure measurements

Abstract: Large inconsistencies in previous microchannel pressure drop data have motivated the development of a microchannel experimental platform that enables the measurement of pressures inside the microchannel. The system utilizes bulk etched silicon components that integrate pressure-sensing membranes with the microchannel test section. The deflection of the membranes is detected by an off-chip, optical-lever based system that allows the sensors to be calibrated for pressure measurement. The sensor sensitivity can be adjusted after microfabrication is complete, allowing for sensor optimization after fabrication. The sensor can be used in many applications where the fabrication of electrical contacts, piezoresistors and capacitors is problematic. Calibration uncertainties as low as 2% have been obtained during actual use of the system. The presented system resolves many of the issues associated with measuring pressures inside microchannels for the range of hydraulic diameters tested, 25–100 μm. The system has been used to study pressure drop in microchannels and a sample of the results is presented. It has been found that standard models with appropriate assumptions can accurately predict the measured pressure data.

Implantable pressure sensor with pacing capability

Abstract: Devices and methods for left ventricular or biventricular pacing plus left ventricular pressure measurement. For example, a pacing lead having a combined electrode and pressure sensor assembly may be used for left ventricular (LV) pacing and pressure measurement. The assembly may include one or more electrodes, a pressure sensor, and a pressure transmission catheter. Such a pacing lead is particularly suitable for biventricular pacing and may be incorporated into a cardiac resynchronization therapy (CRT) system, for example.

The Pressure Distribution in Thermally Bistable Turbulent Flows

Abstract: We present a systematic numerical study of the effect of turbulent velocity fluctuations on the thermal pressure distribution in thermally bistable flows. The turbulent fluctuations are characterized by their rms Mach number M (with respect to the warm medium) and the energy injection (forcing) wavenumber kfor = 1/l, where l is the injection size scale in units of the box size L = 100 pc. The numerical simulations employ random turbulent driving generated in Fourier space rather than starlike heating, in order to allow for precise control of the parameters. Our range of parameters is 0.5 ≤ M ≤ 1.25 and 2 ≤ kfor ≤ 16. Our results are consistent with the picture that as either of these parameters is increased, the local ratio of turbulent crossing time to cooling time decreases, causing transient structures in which the effective behavior is intermediate between the thermal-equilibrium and adiabatic regimes. As a result, the effective polytropic exponent γe of the simulations ranges between ~0.2 and ~1.1, and the mean pressure of the diffuse gas is generally reduced below the thermal equilibrium pressure Peq, while that of the dense gas is increased with respect to Peq. The fraction of high-density zones (n > 7.1 cm-3) with P > 104 cm-3 K increases from roughly 0.1% at kfor = 2 and M = 0.5 to roughly 70% for kfor = 16 and M = 1.25. A preliminary comparison with the recent pressure measurements of Jenkins in C I favors our case with M = 0.5 and kfor = 2. In all cases, the dynamic range of the pressure in any given density interval is larger than one order of magnitude, and the total dynamic range, summed over the entire density range, typically spans 3-4 orders of magnitude. The total pressure histogram widens as the Mach number is increased, and moreover develops near-power-law tails at high (low) pressures when γe 0.5 (γe 1), which occurs at kfor = 2 (kfor = 16) in our simulations. The opposite side of the pressure histogram decays rapidly, in an approximately lognormal form. This behavior resembles that of the corresponding density histograms, in spite of the large scatter of the pressure in any given density interval. Our results show that turbulent advection alone can generate large pressure scatters, with power-law high-P tails for large-scale driving, and provide validation for approaches attempting to derive the shape of the pressure histogram through a change of variable from the known form of the density histogram, such as that performed by Mac Low et al.

Fluid Supply Method and Apparatus

Abstract: A method and apparatus for supplying fluid to a deposition device or printhead using the through flow principle. The pressure of fluid entering and exiting the printhead is controlled directly at the printhead by respective pressure controllers, preferably a transducer and control system or a weir. The pressure controllers can be integrated together and mounted on or further integrated with the printhead. The supply system preferably forms a closed loop including a remote reservoir, and the entire system can be arranged such that the overall free surface of fluid is exposed on average to a negative gauge pressure.

Transient pressure induced by laser ablation of toluene, a highly laser-absorbing liquid

Abstract: Transient processes of laser ablation of a highly laser-absorbing liquid, toluene, were investigated by directly measuring (by using a fast-response pressure gauge) the transient pressure caused by toluene ablation under KrF laser irradiation . The results were compared with time-resolved images . The peak pressure P due to a shock wave decreased slowly with increasing distance d for d=100–1000 μm:P∝d-0.33. By extrapolating P to d=8.9 μm, the optical penetration depth of toluene at λ=248 nm, the estimated initial pressure due to toluene ablation was 65 MPa at 1.0 J cm-2 pulse-1. The estimated initial pressure increased linearly with the fluence. These results help clarify the mechanism of laser-induced backside wet etching.

Energy of power spectral density function and wavelet analysis of absolute pressure fluctuation measurements in fluidized beds

Abstract: The standard deviation of pressure fluctuations is always as a benchmark to characterize fluidized bed, especially in identifying the transition velocities and flow regimes. In this study, the energy of power spectral density function (PSDF) was proved to be a new alternative tool to effectively analyse the pressure fluctuations. Also, the wavelet analysis was significant to deal with the signals in multi-resolution decomposition and in identification of transition velocities and flow regimes. The results from the normalized energy of PSDF and wavelet analysis are in good agreement with the standard deviation analysis.

Pressure detector for fluid circuits

Abstract: A pressure measurement device usable for monitoring pressure of fluids such as blood, waste, and replacement fluid in a blood treatment system provides a reliable signal and other benefits by virtue of a number of features of the various embodiments disclosed. The pressure of fluid carried by a vessel or tube is measured by measuring a change in shape of the vessel or tube via a sensor element contacting it. Materials, shape, and mechanical support cooperatively ensure that the little inelastic strain occurs and pressure measurements are repeatable. The embodiments are compatible with the use of disposable vessels and tubes.

Fabrication and temperature coefficient compensation technology of low cost high temperature pressure sensor

Abstract: For the purposes of pressure measurement at high temperature in oil drilling industry as well as in other industrial measurement and control systems, the strain gauge chip of piezoresistive pressure sensor is designed based on separation by implanted oxygen (SIMOX) SOI (silicon on insulator) technology, and then fabricated in the micro-machining work bay. Some kinds of sensor mechanical structures are designed for different customers and conditions. The thermal coefficients of expansion (TCE) mismatches between different materials within the high-pressure sensor system are investigated. The sensor is fabricated successfully by using high temperature packaging process. The temperature coefficient of sensitivity (TCS) and temperature coefficient of offset (TCO) compensation circuitry is demonstrated. Based on experimental data, the sensor is tested with high accuracy and good stability.

Differential pressure measurement using backside sensing and a single ASIC

Abstract: Differential pressure sensor systems and methods are disclosed, including an absolute pressure sensor composed of a plurality of pressure sense die for detecting sensed media, wherein each of the pressure sense die possess a back side and a front side and are respectively associated with a plurality of varying pressures. The sensed media are applied only at the backside of the pressure sense die, thereby preventing wire bonds and active regions associated with the front side of the pressure sense die from exposure to sensed media and attack from acids and abrasive chemicals associated with the sensed media.

A non-invasive capacitive sensor strip for aerodynamic pressure measurement

Abstract: This paper presents a capacitive pressure sensor strip implemented in general purpose printed circuit board (PCB) technology based on a thin 3D structure composed of polyimide, woven glass reinforced epoxy resin (FR4) and metal layers. Multiphysics finite elements method (FEM) simulations have been performed over the proposed structure in order to develop a time-dependent electrical and mechanical model that can be easily used to tailor the characteristics to the application. The device targets a wide class of fluid dynamics applications, being non-invasive, comformable and smart for placement. The device simulations are herein validated by experimental wind tunnel measurements and compared with figures obtained on a wing profile by conventional electromechanical pressure transducers. This approach is one of the first example of fully embedding and electronically controlled fluid flow monitoring apparatus that could be used in replacement of state of the art mechanical systems.

Convenient optical pressure gauge for multimegabar pressures calibrated to 300GPa

Abstract: The accurate measurement of pressure by a straightforward and inexpensive optical procedure has been needed in the multimegabar region since static pressures over 216GPa, 361GPa, 420GPa and 560GPa were obtained in the diamond anvil cell. Here, a simple optical pressure gauge based on the Raman shift of the diamond at the center of a diamond tip at the diamond–sample interface is calibrated against a primary gauge (Pt isotherm at 300K from shock data) to 300GPa, thus enabling researchers who do not have a synchrotron to conveniently measure pressure with an optical scale from 50to300GPa.

Fiber Optic Pressure Sensor with Self-compensation Capability for Harsh Environment Applications

Abstract: A novel fiber optic pressure sensor system with self-compensation capability for harsh environment applications is reported. The system compensates for the fluctuation of source power and the variation of fiber losses by self-referencing the two channel outputs of a fiber optic extrinsic Fabry-Perot interfrometric (EFPI) sensor probe. A novel sensor fabrication system based on the controlled thermal bonding method is also described. For the first time, high-performance fiber optic EFPI sensor probes can be fabricated in a controlled fashion with excellent mechanical strength and temperature stability to survive and operate in the high-pressure and high-temperature coexisting harsh environment. Using a single-mode fiber sensor probe and the prototype signal-processing unit, we demonstrate pressure measurement up to 8400 psi and achieved resolution of 0.005% (2σ=0.4 psi) at atmospheric pressure, repeatability of ±0.15% (±13 psi), and 25-h stability of 0.09% (7 psi). The system also shows excellent remote operation capability when tested by separating the sensor probe from its signal-processing unit at a distance of 6.4 km.

Contribution to characterisation of insect-proof screens: experimental measurements in wind tunnel and cfd simulation

Abstract: The aim of the present study was to evaluate geometrical characteristics and airflow resistance of eleven different insect-proof screens by three different experimental procedures: equipment based in water-flow suction, low-speed wind tunnel, and CFD simulations. The two first arrangements had the same principle, in that air was forced through the test samples in order to create a pressure drop. Last analyses were carried out by numerical simulations of airflow through insect-proof screens using a commercial fluid dynamics code based in Finite Element method (ANSYS/ FLOTRAN v8.0). Previously, an analysis images system, called EUCLIDES v1.1, was designed with MS Visual Basic 6.0 running under MS Windows, for the analysis of the screens samples images captured with a microscope. A geometrical characterization of the eleven screens materials was carried out using this software tool. The software allows to determine all the geometric parameters that characterize the screens, as thread diameter and distances between two adjacent threads in two directions, from the four coordinates that defined each pore. The results obtained in this work show that the eleven screens can be classed in three groups, corresponding with the fibre density, with similar porosity and airflow properties (permeability and inertial factor). However, sample 8 has a small thread diameter and screen thickness that decreased the pressure drop coefficient. The results suggest that equations based on the porosity of the screen and the Reynolds number can be used to calculate the pressure drop coefficient. INTRODUCTION In an integrated pest management system, exclusion of pests should be one of the first tactics considered to reduce the need for other control measures. Whiteflies (Bemisia tabaci) and thrips (Frankliniella occidentalis) are among the most important pests of greenhouse crops in Almeria (Acebedo, 2004). As in other parts of the world (Taylor et al., 2001), most of the losses produced in Spain by Bemisia tabaci are due to its role as a virus vector (Guirao et al., 1997). Tomato yellow leaf curl virus (TYLCV) was reported for the first time in Spain in the autumn of 1992 (Moriones et al., 1993). Because of pest-acquired resistance, management practices that rely on insecticides are growing increasingly less effective, and less environmentally and economically appropriate. Reductions in pest populations (Baker and Jones, 1989) and lower incidence of insect-transmitted diseases (Baker and Jones 1989, 1990) have been documented when screening is used. Exclusion screens for the greenhouse may become a necessary alternative to pesticide use. However, airflow resistance, primarily a function of hole or mesh size, reduces the ventilation rate. Many efficacious screens have a small hole size and are more resistant to airflow than are more open-meshed screens (Bethke and Paine, 1991; Bell and Baker, 2000). The aim of the present study was to evaluate geometrical characteristics and airflow resistance of eleven different insect-proof screens by three different experimental procedures: low-speed wind tunnel, equipment based in water-flow suction, and CFD simulations. Proc. IC on Greensys Eds.: G. van Straten et al. Acta Hort. 691, ISHS 2005 442 MATERIALS AND METHODS In order to obtain the airflow characteristics of porous screens we measured the pressure drop caused by the insect-proof screen for different velocities in the range 0.1 to 12 m s. The first experiments were carried out in a wind tunnel with a cross-section of 420 mm × 360 mm and 5.2 m long. A helicoidally fan of 460 mm diameter driven by multi-speed 2.2 kW 3-phase induction electric motor HCT-45 (Sodeca S.A., Sant Qurze de Besora, Spain). Airflow was controlled by a Micromaster 420 AC inverter (Siemens Energy & Automation Inc., Alpharetta, USA) that allow decreased the fan motor speed from 0 to 2865 rpm, with digital microprocessor control and a set point resolution of 0.01 Hz. The static pressure drop through the screen was measured by a pressure transducer SETRA (Setra Systems Inc., Boxboruogh, USA), connected to two Pitot tubes, one 430 mm upstream and one 430 mm downstream from the tested screens (Terres-Nicoli et al., 2004.). Air velocity was determined connecting the static pressure and total pressure tapings of the upstream Pitot tube to another pressure transducer MKS (MKS Instrument Inc., Andover, USA). For air velocity lower to 1 m s the screen samples (diameter 115 mm) were mounted in a test duct (length 220 mm) separated by PVC rings of 10 mm thickness, 70 mm internal and 115 mm external diameter containing 20 screen samples (Fig. 1). Originally, the downstream tube was connected to the upper side of a water reservoir by a flexible pipe. The measurements are based on the pressure drop caused by natural suction of air through the samples as a result of water flow induced by gravity (Miguel et al., 1997). Subsequently, we repeated the test for the sample number 1, for air velocity between 0.1 and 1 m s, connecting the downstream tube to a fan NMB-4715KL (NMB Technologies Inc, Chatsworth, USA). The airflow supplied by the fan was regulated by controlling the rotational speed of the fan, function of the voltage that was varied from 3 V to 12 V with a DC power supply HY-3010 (DavJones Technology, Singapore). No statistical differences were observed between the tests made with the fan and the water reservoir for sample number 1. For reason of simplicity, we use the fan for air supply with the rest of samples (from 2 to 11). The pressure drop was measured using an inclined tube manometer AIRFLOW type 504 (Airflow Developments Limited, Buckinghamshire, England). The manometer, with a full-scale range of 125 Pa and an accuracy of 1 Pa, was connected to two Pitot tubes (150 mm upstream and 90 mm downstream). The measurement of air velocity was taken using a multifunction digital handheld instrument TESTO® 445 (Testo S.A., Cabrils, Spain) with a hot-bulb probe. This instrument has a measurement range from 0 to 10 m s with an accuracy of ±0.03 m s and resolution of 0.01 m s. The equipment also contains a temperature probe (thermistor NTC) with a range of –20 to 70oC and an accuracy of ±0.4oC. Last analyses were carried out by numerical simulations of airflow through insectproof screens using a commercial fluid dynamics code based in Finite Element Method (ANSYS/FLOTRAN v8). In the simulation, it was assumed that a woven screen comprises a large number of small pores, and a similar flow passed through each. The pore was modelled as the intersection of four cylinder (Teitel and Shklyar, 1998). Previously, an analysis images system, named EUCLIDES v1.1, was designed with MS Visual Basic 6.0 running under MS Windows, for the analysis of the screens samples images captured with a microscope DMWB1 (Motic Spain S.L., Barcelona, Spain). We used a plan 4X achromatic lens that provided images with a resolution of 0.0105 mm/pixel. Once the image was captured a different program (Photo Finish 4.0) was used to convert the images in true colour to black and white. A geometrical characterization of the eleven screens materials was carried out using the EUCLIDES software. This software allows to determine all the geometric parameters that characterize the screens, as thread diameter, d, and distances between two adjacent threads in two directions, Dhx and Dhy, from the four coordinates that defined each pore, recognised automatically by the software. The program also measures the porosity as the ratio of geometric pore area, calculated from the vertices coordinates, to whole area. For all screens we analysed three samples of 1 cm size.

Method and apparatus for continuous readout of Fabry-Perot fiber optic sensor

Abstract: A pressure measurement system and method are described. The system uses a tunable laser and a Fabry-Perot sensor with integrated transducer. A detector senses the light modulated by the Fabry-Perot sensor. A signal conditioner, which can be located up to 15 km away, then uses the detector signal to determine the displacement of the diaphragm, which is indicative of pressure exerted against the diaphragm. Use of a temperature sensor to generate a signal, fed to the signal conditioner, to compensate for temperature is also contemplated.

System and method for pressure measurement

Abstract: A system and method for pressure measurement may include the ability to readily produce a pressure measurement system. In one general aspect, pressure measurement 100 may include a signal-converting circuit 500 that includes a coupler 510, a signal biaser 550, and a signal span adjuster 560. The coupler is operable to receive a pressure-representative signal, and the signal biaser includes a thermally-insensitive voltage divider that facilitates biasing the pressure-representative signal. The signal span adjuster is coupled to the coupler and the signal biaser and includes a thermally-insensitive voltage divider that facilitates adjusting the span of the pressure-representative signal.

Final Report on Key Comparison CCM.P-K7 in the range 10 MPa to 100 MPa of hydraulic gauge pressure

Abstract: This report describes a CCM key comparison of hydraulic pressure standards of nine National Metrology Institutes that was carried out in the period from November 2002 to June 2004 in order to determine their degrees of equivalence in the range 10 MPa to 100 MPa of the gauge pressure. The pilot laboratory was PTB. The primary pressure standards were pressure balances of different design equipped with piston-cylinder assemblies operated in freedeformation, controlled-clearance or re-entrant operation mode. The transfer standard was a pressure balance equipped with a piston-cylinder assembly and a mass set. The pressuredependent effective areas of the transfer standard at specified pressures were reported by the participants and led to the reference values calculated as medians. All participants’ results agree with the reference values and with each other within the expanded uncertainties calculated with a coverage factor 2, most of them even within their standard uncertainties. In addition, the results were analysed in terms of the zero pressure effective area and the pressure distortion coefficient. Also for them agreement within expanded uncertainties (k=2) is observed. The results of the comparison demonstrate equivalence of the laboratory standards and support their measurement capability statements.

Fiber tip based sensor system for measurements of pressure gradient, air particle velocity and acoustic intensity

Abstract: A fiber optic sensor system for pressure measurements where the design permits multiplexity on the input side of the system and the optical part of the system, which has a sensor Fabry-Perot interferometer and a read-out interferometer, is based on low coherence fiber-optic interferometry techniques. This permits a high dynamic range and low sensitivity to the wavelength fluctuation of the light source as well as to the optical intensity fluctuations. The system includes fiber tip based Fabry-Perot sensors, where each sensor includes a diaphragm as the transducer. A combined pressure gradient sensor, air particle velocity sensor, as well as acoustic intensity sensor is built based on the fiber tip based Fabry-Perot sensors.