Showing papers on "Pressure measurement published in 1989"

Downhole tool for determination of formation properties

Abstract: The apparatus of the present invention relates to a down hole tool capable of extraction of valid samples and making pressure measurements useful in calculating formation permeability. The tool incorporates the features of a straddle packer to allow formation fluid specimens to be taken at large flow rates without depressing the pressure below the formation fluid bubble point. When used in combination with a pressure probe the tool is used to obtain meaningful permeability readings in a larger radius area than previously permitted with known designs. Additionally, the apparatus of the present invention allows flow control during the creation of the pressure pulse which enhances extraction of valid samples and the permeability determination. The apparatus may be modularly constructed so that in a single descent of the tool, a pressure profile of the zone of interest can be made, a fluid analysis can be made at each station, multiple uncontaminated fluid samples can be withdrawn at pressures above the bubble point, local vertical and horizontal permeability measurements can be made at each station, a packer module can be set at a location dictated by previous measurements and a large scale pressure build up test can be performed.

Rotor-stator interaction in a diffuser pump

Abstract: The interaction between impeller blades and diffuser vanes in a diffuser pump was investigated. Steady and unsteady pressure measurements were taken on the diffuser vanes, and the shroud wall of a vaned and a vane less diffuser. Steady, unsteady, and ensemble averaged unsteady data, as well as frequency spectra are presented. The measurements were made for different flow coefficients, shaft speeds, and radial gaps between impeller blade trailing and diffuser vane leading edge (1.5% and 4.5% based on impeller discharge radius). The resulting lift on the vane, both steady and unsteady, was computed from the pressure measurements at mid vane height. The magnitude of the fluctuating lift was found to be greater than the steady lift. The pressure fluctuations were larger on the suction side than on the pressure side attaining their maximum value, of the same order of magnitude as the total pressure rise across the pump, near the leading edge. Pressure fluctuations were also measured across the span of the vane. and those near the shroud were significantly smaller than those near the hub. The pressure fluctuations on the shroud wall itself were larger for the vaned diffuser than a vaneless diffuser. Lift, vane pressure, and shroud wall pressure fluctuations decreased strongly with increasing radial gap.

High‐pressure measurements at moderate temperatures in a diamond anvil cell with a new optical sensor: SrB4O7:Sm2+

Abstract: The 0.255 A/kbar linear pressure shift of the intense, narrow, and well‐isolated 5D0‐7F0 (named 0‐0) emission line of SrB4O7:Sm2+ (at 6854.1 A in ambient conditions) is proposed as a new optical pressure gauge for the diamond anvil cell. The pressure determinations can be made with the same experimental devices as those currently used for the ruby sensor. The good accuracy results from the singlet character and a small linewidth which is no more than 2.5 A up to 200 kbar in a 4:1 methanol:ethanol mixture, provided the linewidth is ‘‘relaxed’’ through thermal cycles. Such a process can probably be of general interest for this purpose. In nonisostatic media, a similar pressure coefficient and a broadening of ∼0.1 A/kbar are obtained. This broadening does not greatly disturb the pressure measurements, at least up to 200 kbar. High‐pressure determinations up to 400 °C are also shown to be more accurate than with the ruby, owing to the very limited temperature effect on the wavelength (−0.001 A/°C) and linewid...

On-board tire pressure indicating system performing temperature-compensated pressure measurement, and pressure measurement circuitry thereof

Abstract: A reliable indication of temperature-compensated pressure is provided from each of the wheels of a vehicle to an operator within the vehicle. A piezoresistive transducer bridge is supplied by a constant current source in one embodiment, and by a voltage of constant amplitude in another embodiment. Voltage to the bridge is reversed on a periodic basis. The use of constant current enables compensation for temperature-induced drift in transducer bridge output. The use of constant voltage enables compensation for ambient temperature, and provides an absolute, rather than a relative indication of pressure or "flatness" within the tire. Voltage polarity reversal permits compensation of amplifier offset voltage. Energy is transmitted to an from the wheel by means of a tuned circuit which is excited by a primary coil when the vehicle's engine is running. The secondary coil mounted on the wheel may be either short-circuited or selectively opened and closed to alter the operation of the primary coil, thus providing an indication of tire pressure, that indication being detected and processed by suitable microcomputer circuitry which may exist on board the vehicle. Most of the active circuit elements of the invention may be implemented in a single monolithic integrated circuit, which can be attached to a tire valve.

Gas kick detector

Abstract: Methods for the early detection of gas kicks in marine risers (10) include monitoring a downhole absolute pressure and a downhole differential pressure of a riser section (11) positioned just above the blowout preventer (18). The absolute pressure is used to calculate an average density of mud or mud/gas mixture in the entire riser (10). The differential pressure across the riser section (11) is used to calculate an average density of mud or mud/gas mixture in riser section (11). An unfavorable comparison between the calculated density for the mud or mud/gas mixture in the riser section (11) and the calculated density for the mud or mud/gas mixture in the entire riser (10) is used to detect the onset of a gas kick and to alert the operator. Alternatively, the measured differential pressure across the riser section (11) can be compared with an expected downhole differential pressure. Unfavorable comparisons of the measured and expected differential pressures indicate the onset of a gas kick.

Combination air data probe

Abstract: A combination air data probe performs a number of different pressure measurements from a single structure Measurements of total pressure and total temperature are performed in an improved structural configuration which renders these measurements substantially insensitive to aircraft angle of attack Static temperature is computed free of recovery factor error because of compensatory effects in the pressure and temperature signals Another part of the probe provides measurement of static pressure and pressures for determining angle of attack

The technology of diamond anvil high-pressure cells. II: Operation and use

Abstract: For pt.I see ibid., vol.22, no.11, p.913-23, Nov. 1989. The operation and use of diamond anvil cells is discussed. Experimental details pertaining to the assembly of cells preparation of gaskets, compressing media, sample preparation and handling, pressure measurement and types of spectroscopic and electrical measurement which can be carried out are given.

Method of making an ultraminiature pressure sensor

Abstract: A capacitive pressure sensor suitable for making highly sensitive, low pressure measurements is disclosed. The sensor may be mounted into a 0.5 mm OD catheter suitable for multipoint pressure measurements from within the coronary artery of the heart. The sensor employs a tranducer which consists of a rectangular bulk silicon micro-diaphragm several hundred microns on a side by two microns thick, surrounded by a supporting bulk silicon rim about 12 microns thick. Both the diaphragm and the rim are defined by a double diffusion etch-stop technique. The transducer fabrication process features a batch wafer-to-glass electrostatic seal followed by a silicon etch, which eliminates handling of individual small diaphragm structures until die separation and final packaging. An addressable read-out interface circuit may be used with the sensor to provide a high-level output signal, and allows the sensor to be compatible for use on a multisite catheter having only two electrical leads.

Simulation of circular silicon pressure sensors with a center boss for very low pressure measurement

Abstract: A characteristics simulation method of circular silicon-diaphragm piezoresistive pressure sensors was developed to obtain accurate sensors for very-low-pressure measurement. The anisotropic stress-strain relationship of a silicon single-crystal plate and the nonlinear characteristics of silicon piezoresistive gauges were considered. Nonlinear deflection and strain formulas of circular silicon diaphragm sensors with a center boss and sensors with a center boss and ribs were derived by taking the effects of the large deflection and the support stiffness of the diaphragms into account. Based on these considerations, the characteristics of the sensors were simulated. The simulated results show good agreement with the observed results and indicate that output voltage can be greatly increased while maintaining low nonlinearity even in the low-pressure range by narrowing the rib width and thinning the diaphragm thickness of sensors with a center boss and ribs. This is because the rib strain that produces output voltage is increased while maintaining small deflection by using this type of sensor. >

Flow Measurement with Trapezoidal Free Overfall

Abstract: The trapezoidal free overfall is analyzed by the onedimensional momentum equation, including an assumed pressure distribution at the brink. The pressure distribution is based on previous measuremen...

Experimental analysis of catheter-manometer systems in vitro and in vivo.

Abstract: The static and dynamic responses of two combinations of transducer amplifiers, pressure transducers, resonance elimination devices, extension tubing, and transcutaneous cannulae were tested in vitro using a sine-wave pressure generator, and in vivo by square-wave pressures generated by a "fast-flush" device. In addition, carotid arterial blood pressure waveforms recorded by these systems in sheep, at two different heart rates, were compared with those simultaneously recorded with a catheter-tip pressure transducer. A new term, "Working Heart Rate" is defined and allows for the prediction of the maximum heart rate up to which a system of given frequency response and damping coefficient should be accurate. When tested in vitro, all the monitoring systems were underdamped and resonated. The performance of all systems was improved by inclusion of an adjustable resonance elimination device but impaired by a nonadjustable resonance eliminator or by recording with an electronically filtered amplifier. When tested in vivo, the accuracy of mean and diastolic blood pressure measurement was not affected by any combination of heart rate, amplifier, length of extension tubing, or use of resonance eliminators. Both resonance elimination devices improved the performance of all systems. In contrast to predictions based on frequency response and damping, the smallest errors in systolic blood pressure were recorded using the electronic filter or the nonadjustable resonance eliminator. There were considerable and misleading differences between the frequency responses and damping coefficients calculated in vitro and those, for the same systems, derived from the in vivo fast-flush tests. It is concluded that the most accurate and consistent readings of systolic blood pressure will be achieved with the use of either an electronic filter or a nonadjustable resonance eliminator.

In-situ crystal growth and neutron four-circle diffractometry under high pressure

Abstract: Pressure cells designed for work on four-circle diffractometers equipped with an Eulerian cradle and pressures up to 2.5 GPa are described. Single crystalline sapphire anvils allow the optical inspection of the sample crystals, e.g., during in-situ crystal growth and the pressure measurement with the ruby fluorescence technique. Experiments on normal and deuterated ice VI are reported.

Siphon mechanism in collapsible tubes: application to circulation of the giraffe head.

Abstract: Controversy exists over the principles involved in determining blood flow to the head of a giraffe, specifically over the role of gravity pressure (pgh) in the collapsible jugular vein in facilitating uphill flow in arteries. This study investigated the pressures within vertically oriented models containing both rigid and collapsible tubes. An inverted U tube was constructed (height = 103 cm) of thick rubber tubing in the ascending limb and collapsible dialysis tubing in the descending limb. Water flow was induced by a variable speed pump maintained at the reservoir level such that the descending limb was partially collapsed. Pressure measurements were made at various levels within the U tube by two methods: 1) with the transducer at same level as the tip of the water-filled catheter and 2) with the transducer at the reservoir level. During flow, the pressure at any point was nearly atmospheric along the length of the descending limb. Such methods of obtaining pressure indicated that the pressure gradient within the partially collapsed descending limb was the sum of viscous flow pressure (P1-P2 of Poiseuille) and gravitational pressure (pgh). To study the facilitatory effect of a siphon, the descending limb was compared with a horizontally placed limb (length = 100 cm), and the flow was kept constant. Calculations of hydraulic "work" (pressure x flow) indicated that with a partially collapsed descending limb, work of the pump was reduced by 15% compared with uphill flow to the elevated horizontal position. It is concluded that the siphon mechanism operates in a partially collapsed descending limb of a siphon loop.

Pressure Trace Knock Measurement in a Current S.I. Production Engine

Abstract: This paper describes a study in which a spark-plug-mounted pressure transducer and an in-cylinder flush mounted pressure transducer were used to monitor the combustion pressure in a modern four cylinder engine during knocking and normal full load operation over a speed range of 1800 RPM to 4000 RPM. This engine features paid combustion and small knock pressure peaks. Pressure trace knock detection algorithms are compared with the output of the standard knock sensor (accelerometer) mounted on the intake manifold of the engine.

Measuring device forming part of a test device for filter systems, test device and test method

Abstract: In the case of a measuring device (1) forming part of a test device (1, 14) for filter systems (14), in which the filter system (14) to be tested has at least one filter housing with a fluid inlet and outlet, between which a fluid-permeable filter element (14') is arranged so as to separate them, the measuring device (1) contains control means, measuring means, memory storage means, computation means and circuit means using which the individual test parameters for the test methods for bubble-point determination, for the pressure-holding test, for the diffusion test and for the system self-test as well as other tests can in each case be input as a menu program into the measuring device (1) and processed so that the only parameters determined by test techniques are those which are directly necessary to the chosen test method. Additional parameters can be selected and retrieved by input individually or in blocks, as required. In order to carry out the system self-test, means are provided which make a comparison between the test data programmed in and the operating pressure, the test pressure, and the maximum bubble point, and display the results and/or recommendations as a guide to the user in the display unit (2'). A pressure measurement is carried out with temperature compensation and, if required, using at least two pressure gradients. In this case, reliable information regarding individual failures in multiple systems is obtained by dividing the measurement results. By pressure measurement at the housing inlet ... Original abstract incomplete.

Pressure sensor useable in oil wells

Abstract: A pressure sensor of the present invention can perform pressure measurements under very severe mechanical and thermal conditions. It comprises a cell carrying a strain-measuring circuit. The cell is placed inside a body and is put into contact with the pressure to be measured. The cell has a hermetically sealed internal chamber inside which pressure is set to a predetermined reference value. The outside surface of the cell is subjected to the pressure to be measured. The cell is constituted by two half-shells joined together according to a join plane. The cell is preferably made of sapphire, with the crystal axis of the sapphire being perpendicular to the join plane so as to obtain isotropic stresses. A strain-gauge circuit is deposited on a plane surface of one of the half-shells, parallel to the join plane. The sensor is particularly suitable for testing oil deposits.

Conductance modulation method for the measurement of the pumping speed and outgassing rate of pumps in ultrahigh vacuum

Abstract: A new method, named the conductance modulation method (CM method), was developed for the measurement of pumping speeds (intrinsic and net) and outgassing rates in vacuum systems. The details of the formulation and the procedure of the CM method are described. The principle of the method lies in the measurement of the pressure modulation with the change of the conductance between a chamber and a pump. The pumping speed is obtained from the ratio of the modulated pressures and the value of the conductance without measurements of absolute pressures. This feature makes the method quite appropriate for measurements in ultrahigh vacuum. The CM method was applied to the measurement of the gas balance in a vacuum system pumped with a Ti getter pump. The intrinsic and the net speed of the Ti getter pump were measured for H2 in a wide pressure range down to ultimate pressure under various conditions of getter films and the amount of H2 sorbed. The outgassing rates from the wall of the chamber and the pump were simultaneously evaluated. These results confirmed the usefulness of the CM method for the quantitative analysis on the gas balance in vacuum systems.

In-flight measurement of static pressures and boundary-layer state with integrated sensors

Abstract: Advanced wing designs for transport aircraft using adaptive geometries for performance optimization and load control need reliable integrated sensors for feedback to the control system. More efficient air data sensing, eliminating the pitot-static piping, is also required, as in highly integrated modern flight management systems. Absolute pressure transducers from different manufacturers were tested and adapted to the flight-test environment. In laboratory and different flight tests, their applicability for steady measurements was proven in comparison to scanivalves. It was shown that sensing of pressure fluctuations in the buffet regime will improve the prediction of operational buffet limits. The pressure transducers were also used to investigate the laminar/ turbulent transition in the attachment-line flow of a swept wing in comparison to hot-film probes and were found to be an effective tool for such an experiment.

Method and apparatus for measurement of web tension

Abstract: The invention concerns a method and apparatus for measuring web tension. The tension of a moving web is measured by lo­cating close to the web (14) a gauging bar (1), which has its outer surface curved in the machine direction of the web (14) and carries pressure measurement sensors (2) in holes (3) formed into the bar. An air-cushion is formed between the moving web (14) and the curved surface, wherein the pressure is proportional to the tension of the web (14). The tension of the web (14) is measured in an indirect way by gauging the air-cushion pressure. The apparatus capable of implementing the method has an apparatus (7) required for the generation of a reference pressure, and the pressure measurement apparatus is used for measuring the pressure difference between said reference pressure and the air-­cushion pressure.

Pressure sensitive optical fiber having optimized coatings

Abstract: The acoustic pressure sensitivity of an optical fiber waveguide is maximized by surrounding it with an outer coating which is selected from a material having high Young's modulus and low bulk modulus.

Volumetric measurement of tank volume

Abstract: A method for determining the volume of compressible gas in a system including incompressible substances in a zero-gravity environment consisting of measuring the change in pressure (ΔP) for a known volume change rate (ΔV/Δt) in the polytropic region between isothermal and adiabatic conditions. The measurements are utilized in an idealized formula for determining the change in isothermal pressure (ΔPiso) for the gas. From the isothermal pressure change (ΔPiso) the gas volume is obtained. The method is also applicable to determination of gas volume by utilizing work (W) in the compression process. In a passive system, the relationship of specific densities can be obtained.

Gas pressure gauge and pressure measuring method

Abstract: A process for measuring pressure, preferably vacuum is described. The measuring signals from a heat conduction gauge and the measuring signals from a gas friction gauge are processed to a common measuring signal preferably by multiplication. They are linearly superimposed or added. The heat conduction gauge is preferably a Pirani gauge and the gas friction gauge is preferably a tuning fork quartz gauge.

Free‐surface velocity measurement of shock‐compressed alumina powder compact using a Fabry–Perot interferometer

Abstract: A Fabry–Perot interferometer system was used to measure the free‐surface velocity of α‐alumina powder compact. In situ pressure profile measurements using a pair of manganin gauges were also carried out to clarify the compaction process during compression and stress release. The Fabry–Perot system indicates that the reflectivity of the free surface of the powder material does not significantly change during the stress release process. An observed feature of the powder’s stress release curve as determined by the manganin gauge suggests the existence of the residual voids in the shock compressed powder matrix even in the high shock pressure regime.

Airborne and ground based lidar measurements of the atmospheric pressure profile.

Abstract: The first high accuracy remote measurements of the atmospheric pressure profile have been made. The measurements were made with a differential absorption lidar system that utilizes tunable alexandrite lasers. The absorption in the trough between two lines in the oxygen A-band near 760 nm was used for probing the atmosphere. Measurements of the 2-D structure of the pressure field were made in the troposphere from an aircraft looking down. Also, measurements of the 1-D structure were made from the ground looking up. Typical pressure accuracies for the aircraft measurements were 1.5-2 mbar with a 30-m vertical resolution and a 100-shot average (20 s), which corresponds to a 2-km horizontal resolution. Typical accuracies for the upward viewing ground based measurements were 2.0 mbar for a 30-m resolution and a 100-shot average.

Method to determine with a pressure sensor the combustion pressure in a cylinder of a combustion engine

Abstract: The atmospheric pressure is assigned as reference pressure to the sensor signal of a pressure sensor when the piston is in the TDC position for gas exchange. This reference signal and two further sensor signals at predetermined piston positions are used for determining the sensor sensitivity and, by means of the latter, the absolute pressure at any desired piston positions.