Showing papers on "Pressure measurement published in 2001"

Prospective Evaluation of a Method for Estimating Ascending Aortic Pressure From the Radial Artery Pressure Waveform

Abstract: Pressure wave reflection in the upper limb causes amplification of the arterial pulse so that radial systolic and pulse pressures are greater than in the ascending aorta. Wave transmission properti...

Predrill pore-pressure prediction using seismic data

Abstract: 1A predrill estimate of pore pressure can be obtained from seismic velocities using a velocity‐to–pore‐pressure transform, but the seismic velocities need to be derived using methods having sufficient resolution for well planning purposes. For a deepwater Gulf of Mexico example, significant differences are found between the velocity field obtained using reflection tomography and that obtained using a conventional method based on the Dix equation. These lead to significant differences in the predicted pore pressure. Parameters in the velocity‐to–pore‐pressure transform are estimated using seismic interval velocities and pressure data from nearby calibration wells. The uncertainty in the pore pressure prediction is analyzed by examining the spread in the predicted pore pressure obtained using parameter combinations which sample the region of parameter space consistent with the available well data. If calibration wells are not available, the ideas proposed in this paper can be used with measurements made whi...

Nonideal Effects Behind Reflected Shock Waves in a High-Pressure Shock Tube

Abstract: . Shock tubes often experience temperature and pressure nonuniformities behind the reflected shock wave that cannot be neglected in chemical kinetics experiments. Because of increased viscous effects, smaller tube diameters, and nonideal shock formation, the reflected-shock nonidealities tend to be greater in higher-pressure shock tubes. Since the increase in test temperature ( $\Delta T_5$ ) is the most significant parameter for chemical kinetics, experiments were performed to characterize $\Delta T_5$ in the Stanford High Pressure Shock Tube using infrared emission from a known amount of CO in argon. From the measured change in vibrationally equilibrated CO emission with time, the corresponding d $T_5/$ dt (or $\Delta T_5$ for a known time interval) of the mixture was inferred assuming an isentropic relationship between post-shock temperature and pressure changes. For a range of representative conditions in argon (24–530 atm, 1275–1900 K), the test temperature 2 cm from the endwall increased 3–8 K after 100 $\mu$ s and 15–40 K after 500 $\mu$ s, depending on the initial conditions. Separate pressure measurements using a shielded piezoelectric transducer confirmed the isentropic assumption. An analytical model of the reflected-shock gas dynamics was also developed, and the calculated $\Delta T_5$ 's agree well with those obtained from experiment. The analytical model was used to estimate the effects of temperature and pressure nonuniformities on typical chemical kinetics measurements. When the kinetics are fast ( $<300\mu$ s), the temperature increase is typically negligible, although some correction is suggested for kinetics experiments lasting longer than 500 $\mu$ s. The temperature increase, however, has a negligible impact on the measured laser absorption profiles of OH (306 nm) and CH $_3$ (216 nm), validating the use of a constant absorption coefficient. Infrared emission experiments are more sensitive to temperature and density changes, so $T_5$ nonuniformities should be taken into account when interpreting ir-emission data.

Pressure Measurement Device

Abstract: A device measures pressures in animals and humans and includes a pressure transmission catheter (PTC) filled with a pressure transmitting medium and implantable in an area in having a physiological pressure. A transducer communicates with the pressure transmitting medium to provide a pressure signal representing variations in the physiologic pressure on electrical wires. A connecting catheter carries the electrical wires to signal processing and telemetry circuitry, which transmits a telemetry signal representing the pressure signal to a receiver external to the animal or human. A housing holds the signal processing and telemetry circuitry, but the transducer is remote from the housing. The device is particularly useful in measuring venous pressure, pulmonary pressure, bladder pressure, or intracranial pressure without significant head pressure artifact and with a sufficient dynamic response. One embodiment of the PTC includes a multi-durometer stem.

Characteristics of wall pressure fluctuations in separated and reattaching flows over a backward-facing step: Part I. Time-mean statistics and cross-spectral analyses

Abstract: Laboratory measurements were made of wall pressure fluctuations in separated and reattaching flows over a backward-facing step. An array of 32 microphones in the streamwise as well as the spanwise directions was utilized. The statistical properties of pressure fluctations were scrutinized. Emphasis was placed on the flow inhomogeneity in the streamwise direction. One-point statistics such as the streamwise distribution of rms pressure and autospectra were shown to be generally consistent with the prior results. The peak frequency and the fall-off rate of autospectra demonstrated the shear layer-originated nature of pressure fluctuations. The coherences and wavenumber spectra in the streamwise and spanwise directions were indicative of the presence of dual modes in pressure; one is associated with the large-scale vortical structure in the low-frequency region and the other is the boundary-layer-like decaying mode in the high-frequency region.

Radio frequency identification tag tire inflation pressure monitoring and location determining method and apparatus

Abstract: A wireless tire inflation pressure measurement device is used to obtain inflation pressure information for a tire of a vehicle and a signal therefrom may be used for determining the location of the tire. An identifier may be associated with the inflation pressure information for each wheel of the vehicle. Tire rotation speed may be determined by amplitude fluctuations of a radio frequency carrier from a radio frequency transmitter rotating with the wheel. Differences in wheel rotation speeds during a turn may be used in determining the location of each tire of the vehicle. An antenna may be placed on each wheel toward the outer perimeter of the wheel and connected to the radio frequency transmitter. A radio frequency identification (RFID) tag and pressure sensor may be used as the wireless tire inflation pressure measurement device and a RFID pickup coil may be provided in each wheel well for pickup of the inflation pressure signals from each RFID tag on a wheel.

Intracochlear pressure measurements related to cochlear tuning

Abstract: Pressure in turn one of the scala tympani (s.t.) was measured close to the basilar membrane (b.m.) and at additional positions as the pressure sensor approached and/or withdrew from the b.m. The s.t. pressure measured within about 100 μm of the b.m. varied rapidly in space at frequencies around the region’s best frequency. Very close to the b.m. the s.t. pressure was tuned and scaled nonlinearly with sound level. The scala vestibuli (s.v.) pressure was measured at one position close to the stapes within seconds of the s.t. pressure and served primarily as a reference pressure. The driving pressure across the organ of Corti and the b.m. velocity were derived from the pressure data. Both were tuned and nonlinear. Therefore, their ratio, the specific acoustic impedance of the organ of Corti complex, was relatively untuned, and only subtly nonlinear. The impedance was inspected specifically for negative resistance (amplification) and resonance. Both were detected in some instances; taken as a whole, the curre...

Tire inflation pressure monitoring and location determining method and apparatus

Abstract: A wireless tire inflation pressure measurement device is used to obtain inflation pressure information for a tire of a vehicle and a signal therefrom may be used for determining the location of the tire. An identifier may be associated with the inflation pressure information for each wheel of the vehicle. Tire rotation speed may be determined by amplitude fluctuations of a radio frequency carrier from a radio frequency transmitter rotating with the wheel. Differences in wheel rotation speeds during a turn may be used in determining the location of each tire of the vehicle. An antenna may be placed on each wheel toward the outer perimeter of the wheel and connected to the radio frequency transmitter. A radio frequency identification (RFID) tag and pressure sensor may be used as the wireless tire inflation pressure measurement device and a RFID pickup coil may be provided in each wheel well for pickup of the inflation pressure signals from each RFID tag on a wheel.

Method and apparatus using directional antenna or learning modes for tire inflation pressure monitoring and location determination

Abstract: A wireless tire inflation pressure measurement device is used to obtain inflation pressure information for a tire of a vehicle and a signal therefrom may be used for determining the location of the tire. An identifier may be associated with the inflation pressure information for each wheel of the vehicle. Tire rotation speed may be determined by amplitude fluctuations of a radio frequency carrier from a radio frequency transmitter rotating with the wheel. Differences in wheel rotation speeds during a turn may be used in determining the location of each tire of the vehicle. An antenna may be placed on each wheel toward the outer perimeter of the wheel and connected to the radio frequency transmitter. A radio frequency identification (RFID) tag and pressure sensor may be used as the wireless tire inflation pressure measurement device and a RFID pickup coil may be provided in each wheel well for pickup of the inflation pressure signals from each RFID tag on a wheel.

Erratum: “ruby-spheres as pressure gauge for optically transparent high pressure cells”

Abstract: Ruby is widely used as an in siru pressure gauge for optically transparent pressure cells up to the megabar range. Usually ruby chips cut from bulk crystals are used which are ill-characterized and inconvenient to handle and to identify visually. Here we present a systematic study on corundum samples doped with Cr3+ ions with concentration from 60 to 23500 ppm to determine the optimal conditions for the use as an accurate pressure marker. The influence of the excitation wavelength on the luminescence spectra was investigated. These studies led to the synthesis of small (1–50 micrometer) ruby spheres with 3000 ppm chromium concentration. After annealing and a heat treatment to avoid internal strains we find reproducible values of the position and the width of the fluorescence lines. These ruby spheres are not only well suited for a reliable and accurate pressure determination in experiments using diamond anvil cells, but can also be used as an in sihr micro-thermometer in high pressure-low tempera...

Aerodynamic Tip Desensitization of an Axial Turbine Rotor Using Tip Platform Extensions

Abstract: Aerodynamic losses due to the formation of a leakage vortex near the tip section of rotor blades form a significant part of viscous losses in axial flow turbines. The leakage flow, mainly induced by the pressure differential between the pressure side and suction side of a rotor tip section, usually rolls into a streamwise vortical structure near the suction side part of the blade tip. The current study uses the concept of a tip platform extension that is a very short “winglet” obtained by slightly extending the tip platform in the tangential direction. The use of a pressure side tip extension can significantly affect the local aerodynamic field by weakening the leakage vortex structure. Phase averaged, time accurate total pressure measurements downstream of a single stage turbine facility are provided from a total pressure probe that has a time response of 150 kHz. Complete total pressure maps in all of the 29 rotor exit planes are measured accurately. Various pressure and suction side extension configurations are compared against a baseline case. The current investigation performed in the Axial Flow Turbine Research Facility (AFTRF) of the Pennsylvania State University shows that significant total to total efficiency gain is possible by the use of tip platform extensions.Copyright © 2001 by ASME

Temperature-insensitive dual-mode resonant sensors - a review

Abstract: Dual mode excitation of resonators allows the highly accurate measurement of, and compensation for, the effects of temperature, pressure, etc., by means of frequency measurements alone. Frequency can be measured with far higher accuracy than any other quantity. In dual mode excitation, the two excited modes occupy the same volume of quartz, thereby allowing the resonator to sense two measurands simultaneously, e.g., pressure and temperature. This paper reviews the dual-mode technique and its sensor applications.

Differential pressure sensor

Abstract: The invention relates to a differential pressure sensor having a low hysteresis volume Said sensor comprises a sensor element (1), two pressure measuring chambers (21, 31) which lie adjacent to the sensor element, two pressure receiving chambers (22, 32) which are closed by separating membranes (21, 31), and two overload chambers (23, 33) which are separated by an overload membrane (6), said overload membrane (6) comprising a closed outer edge and a closed inner edge and being firmly fixed along said outer and inner edge thereof

Downhole flow meter

Abstract: This invention comprises the use of a variable orifice valve (16) as a flow controller and flow meter. Pressure measurements are taken upstream and downstream of the variable orifice valve (16) by way of a differential pressure measurement mechanism (18). The differential pressure measurement mechanism (18) may comprise two separate absolute pressure measurement devices (23) or a single differential pressure measurement device. Flow rate through the valve (16) is determined from the pressure drop across the valve (16). In wellbores having multiple zones (90), a variable orifice valve (16) together with a differential pressure measurement mechanism (23) may be deployed for each zone (90). The flow rate through each of the zones (90) and at the surface can then be monitored and controlled.

Temperature- and Pressure-Sensitive Paint Measurements in Short-Duration Hypersonic Flow

Abstract: Surface temperatures and pressures were measured on an elliptic cone lifting body in a hypersonic e owe eld using thin-e lm (» 5πm) temperature- and pressure-sensitive paints (TSPs and PSPs ). The tests were conducted in the 48-inch hypersonic shock tunnel (48-inch HST) at Calspan‐University of Buffalo Research Center and were part of a more comprehensive experimental study examining the three-dimensional characteristics of laminar, transitional, and turbulent e ow over the model. Measurement opportunity in the 48-inch HST was limited by the short duration of steady freestream conditions of the driven gas; image acquisition times were » 3 ms. Images of the coatings applied to the broad side of the symmetric elliptic cone were calibrated with in situ static pressure and surface-e lm temperature measurements. The TSP results illustrate the higher heat transfer rates and change in boundary-layer transition over the model surface caused by the nose geometry, and the PSP results show a mild pressure gradient over the interrogated surface region. Submillisecond TSP acquisition using a high-speed imager demonstrated the feasibility of measuring the surface temperature rise.

An Implantable Microsystem for Tonometric Blood Pressure Measurement

Abstract: This paper presents an implantable microsystem for tonometric blood pressure measurement in small animals. The microsystem consists of four major components: (1) a titanium base for supporting a pressure sensor and an interface chip, (2) a micromachined capacitive pressure sensor array, (3) a switched-capacitor interface chip, and (4) a titanium cap. A new micromachining fabrication process has been developed to create capacitive pressure transducers with a flat surface necessary for tonometric pressure measurement. An array of three capacitive sensors is used to increase signal output and improve stability. A custom-designed switched-capacitor CMOS interface circuit is used to measure changes in capacitance. In vitro calibration tests have been performed on the complete cuff using a silastic tube to mimic a pliable blood vessel. A sensitivity of 2 mV/mmHg @ 100 mmHg and a resolution of 0.5 mmHg (based on 1 mV RMS interface chip noise floor) has been obtained. The dimensions of the cuff system 10(L)×6.5(W)×3(H) mm3.

Air-in-line and pressure detection

Abstract: Methods and apparatus for air content and pressure measurement of sample fluid, especially sample fluid in association with an infusion pump. Volume change in a chamber as the chamber transitions between negative and positive pressure relates to the air content in the chamber. In particular, in an infusion pump, the volume change of infusion fluid as it transitions between being under negative pressure and positive pressure within a cassette central chamber, e.g., pumping chamber, relates to the air content in the infusion fluid. The outlet pressure of the cassette central chamber, e.g., blood pressure, can be monitored based on the cassette central chamber pressure.

Non-invasive in vivo pressure measurement

Abstract: Apparatus and methods are disclosed for non-invasive measurement of blood velocity in otherwise inaccessible body regions, and for correlating such measurements with externally applied pressure to detect and/or assess diseases or physiological abnormalities. The blood velocity measurements can be based on the Doppler shift that occurs when an ultrasonic wave is scattered by moving particles within the blood. Since blood vessels have elastic walls, the geometry of the walls, and therefore the flow dynamics, will change in response to elevated in vivo pressure. The change in resistance to blood flow resulting from these pressure induced changes to the blood vessel wall geometry can provide a measure of intracranial pressure, ophthalmic pressure or various other body conditions that affect blood perfusion. Since the blood vessel wall geometry changes rapidly in response to such changes in pressure, the invention can be used to detect hydrocephalus, retinopathy, papilledema and other physiological abnormalities manifested by pressure changes.

Calibration of the R ruby fluorescence lines in the pressure range [0-1 GPa] and the temperature range [250-300 K]

Abstract: The pressure range [&1 GPa] and the temperature range [250–300 K] are commonly used in many science fields like biology, agro-chemistry, pharmacology, or geology. In this paper, the calibration of the ruby R lines of fluorescence is performed in these pressure and temperature ranges, using the melting curve of pure water. The linear shifts of ruby peaks are equal to −0.140cm−1/K and −0.768cm−1/kbar with R1, and to −0.137cm−1/K and −0.779 cm−1/kbar with R2. The accuracy of pressure measurements can be as good as ± 10MPa if the temperature is known with ±0.5 K. Such a precision is achieved if: (1) the position of each peak is determined using an inversion method; (2) daily shifts of the spectrometer are corrected before each acquisition; (3) peak positions of each ruby are known at ambient pressure and temperature.

Apparatus and method for formation testing while drilling using combined absolute and differential pressure measurement

Abstract: A formation testing while drilling (FTWP) apparatus and method are provided for obtaining highly accurate pressure measurements in a well borehole using a combination of an absolute and a differential pressure sensor for obtaining absolute pressure measurments under high temperature gradients. A high accuracy quartz absolute pressure sensor is used during a period of constant temperature. A sensor output defines a start range for differential sensor, which has less absolute accuracy but is less susceptible to temperature effects of high temperature gradients.

A flexible encapsulated MEMS pressure sensor system for biomechanical applications

Abstract: The use of pressure sensors made of conductive polymers is common in biomechanical applications. Unfortunately, hysteresis, nonlinearity, non-repeatability and creep have a significant effect on the pressure readings when such conductive polymers are used. The objective of this paper is to explore the potential of a new flexible encapsulated micro electromechanical system (MEMS) pressure sensor system as an alternative for human interface pressure measurement. A prototype has been designed, fabricated, and characterized. Testing has shown that the proposed packaging approach shows very little degradation in the performance characteristics of the original MEMS pressure sensor. The much-needed characteristics of repeatability, linearity, low hysteresis, temperature independency are preserved. Thus the flexible encapsulated MEMS pressure sensor system is very promising and shows superiority over the commercially available conductive polymer film sensors for pressure measurement in biomechanical applications.

Non-intrusive pressure measurement device for subsea well casing annuli

Abstract: A well data monitoring system which enables annulus pressure and other well parameters to be monitored in the outer annuli (B, C, D) of the well casing program without adding any pressure containing penetrations to the well system. This non-intrusive approach to monitoring pressure and other well parameters in the annuli preserves the pressure integrity of the well and maximizes the safety of the well. In the preferred embodiment an intelligent sensor interrogation system (62) which can be located externally or internally of the pressure containing housing of the wellhead is capable of interrogating and receiving data signals from intelligent well data sensors (56, 58, 60) which are exposed to well parameters within the various annuli (B, C, D) of the well and wellhead program.

Accuracy limitations of lifetime-based pressure-sensitive paint (PSP) measurements

Abstract: PSP systems determine air pressure by measuring the luminescence lifetime of an oxygen-quenched luminophor in a porous matrix. While traditionally lifetime was inferred from measurements at different pressures, it is becoming increasingly common to make direct lifetime measurements by taking images at different points on the luminescence decay curve using a gated camera. Here, the accuracy of the lifetime method is evaluated through theoretical analysis, bench top studies, and small scale wind tunnel tests, with the primary aim of determining whether the lifetime method is suitable for measurements in very low speed flows (Mach/spl sim/0.1). It is found that the luminescence lifetime of a PSP-coated surface can vary from point to point even at constant pressure and temperature. This variation is a significant source of error in low speed measurements, and can be reduced significantly by careful paint application procedures.

Gas flow in microchannels with bends

Abstract: Bends or curves are unavoidable features in fluidic systems due to design or technology constraints. These fluidic elements in a macrochannel always induce secondary flows, which result in pressure loss in addition to frictional loss. In this paper, this phenomenon is investigated on a microscale where flow separation is not expected to develop. A set of microchannels, with the dimensions 20×1×5810 µm3, with a 90° turn at the channel centre, has been fabricated using standard micromachining techniques. Three bend configurations have been tested: miter, curved and double-turn. All the microchannels were integrated with pressure microsensors. Argon gas was passed through the microdevices under an inlet pressure of up to 50 psi, and the mass flow rate was measured for all the devices as a function of the driving pressure drop. The flow rate through the channel with the miter bend, a single sharp turn at a right angle, was found to be the lowest. Pressure distributions along the microchannels were recorded, showing an additional pressure drop across the bends. The largest drop was found in the miter bend with the lowest flow rate. The mass flow rate and pressure measurements indicate that secondary flow could develop in microchannels also due to a bend, contrary to expectations.

Method and system for engine air-charge estimation

Abstract: The air flow into an engine is estimated via a speed-density calculation wherein the volumetric efficiency is estimated on-line. There are three interconnected observers in the estimation scheme. The first observer estimates the flow through the throttle based on the signal from a mass air flow sensor (MAF). The second observer estimates the intake manifold pressure using the ideal gas law and the signal from a intake manifold absolute pressure sensor (MAP). The third observer estimates the volumetric efficiency and provides an estimate of the air flow into the engine.

Improved methods for detecting leaks in pressurized piping with a pressure measurement system

Abstract: A method of detecting a leak in a pipeline system, wherein a measurement is performed to determine the difference in the rate of change of pressure due to a leak between one pressure level and at least one other pressure level, after compensation has been made for thermally induced changes in the pressure in a pressurized pipeline system, including the steps of pressurizing the pipeline system to a first pressure level, and measuring the changes in pressure in the pipeline system that occur over a first measurement period; and pressurizing the pipeline system to at least a second pressure level, and measuring the changes in pressure in the pipeline system that occur over at least a second measurement period. A computation is then performed of the difference in the temperature compensated rate of change of pressure between one pressure level and at least one other pressure level from the measured pressure data at the pressure levels, including a correction for the thermally induced non-linear changes of pressure rate of change of pressure between the pressure levels is computed from the rate of change of pressure measured during the measurement periods (first derivative of the pressure data or rate of change of pressure) and higher order derivatives of the pressure data.

Model Development and Analysis of the Dynamics of Pressure-Sensitive Paints

Abstract: Two models for the dynamic behavior of pressure-sensitive paints are developed. The e rst of the two models is a purely empirical approach to designing a model and compensator. The second model presented encompasses the physics of the process by which an unsteady pressure e eld over the paint layer affects the layer and causes an intensity of e uorescence that is e uctuating in time. Within this second model, two different forms for the static calibration are chosen. The effect of the calibration on the system dynamics is demonstrated. Nomenclature A = amplitude a = pressure-sensitive paint thickness b = intercept of linear Stern ‐Volmer static calibration c = calibration constants D = diffusivity E = activation energy f = calibration function from pressure to intensity g = calibration function from intensity to pressure H = transfer function I = integrated intensity J = intensity per unit thickness j = the complex number, p i1 K = intensity error per unit thickness relative to surface condition M = model order m = oxygen concentration difference relative to surface condition n = oxygen concentration P = pressure T = temperature t = time x = distance from substrate ® = modal states ¸ = eigenvalues ae = solubility ? = time constant A = phase 9 = spatial eigenfunctions ! = frequency

Methods and apparatus for maintaining a pressure within an environmentally controlled chamber

Abstract: A system including a chamber; (102) a variable speed vacuum pump (204) coupled to the chamber; and a pressure controller (202) coupled to the chamber. The pressure controller (202) compares a set point pressure with a pressure measurement for the chamber and adjusts a flow of gas through the pressure controller based on a difference between the pressure measurement and the set point pressure. The system includes a pressure measurement device coupled (126) to the chamber and to the pressure controller, and a main controller coupled to the variable speed vacuum pump, the pressure controller and the pressure measurement device. The pressure measurement device measures a pressure within the chamber and provides a pressure measurement to the pressure controller and the main controller. The main controller adjusts a speed of the variable speed vacuum pump (204); and provides the set point pressure to the pressure controller.