Showing papers on "Pressure measurement published in 1973"

An Optical Fluorescence System for Quantitative Pressure Measurement in the Diamond‐Anvil Cell

Abstract: An optical system for rapid routine pressure measurement is described which utilizes a pressure shift in the sharp R‐line fluorescence spectrum of ruby or similar materials. The system, which consists of a standard polarizing microscope and a 1/4 m monochromator with associated photodetection system, is used with the diamond‐anvil pressure cell, but can be employed with suitable modification in any pressure system which has optical access. The precision of the pressure measurement in a hydrostatic environment up to 100 kilobar is 0.5 kilobar using ruby as the pressure sensor. This precision is better than the accuracy of the present pressure scale above 40 kilobar. The merits of fluorescent materials other than ruby as pressure sensors are also discussed. A description of a Waspaloy diamond cell with some modifications in design is given. This improved cell and associated techniques extends the pressure range in gasketed systems up to 200 kilobar at room temperature and to moderate pressures at 700° C.

Disposable manifold with atmospheric vent

Abstract: A manifold is formed with a plurality of ports for connection to various components such as arterial-venous pressure generators, a syringe, and a source of fluid and pressure sensitive transducers. The manifold includes one or more rotary members which are selectively positioned for interconnecting selected ones of the components. Various sampling, flushing and pressure measuring operations may be performed by use of the manifold. The manifold further includes a venting port arrangement for venting the pressure sensitive transducers to the atmosphere when a pressure measurement is not being taken. This protects the transducer from overpressurization and consequential damage.

A Diode‐Quad Bridge Circuit for Use with Capacitance Transducers

Abstract: A new diode‐quad transducer bridge circuit has been developed which features: (1) a high output that is independent of excitation frequency and waveform; (2) a fractional capacitance (ΔC/Co) resolution of 4.4 × 10−8 at a bandwidth of 10–30 Hz; and (3) the capability of conveniently grounding the transducer. Application to a capacitive transducer for pressure measurements yielded an output resolution of 0.003% corresponding to a pressure resolution of ± 1.5 × 10−4 Torr.

Pressure gauge protector assembly and method

Abstract: A pressure gauge protector assembly is provided for measuring the pressure of a fluid without having the fluid come into direct contact with the pressure-measuring gauge. The assembly includes a transparent casing having an inner cavity in which a flexible diaphragm is mouunted to divide the cavity into two chambers. One of the chambers is provided with inlet and outlet openings so that the fluid to be measured can flow through the first chamber, and the second chamber is provided with an opening which is connected to a pressure-measuring gauge by a fluid conduit. The pressure of the fluid to be measured displaces the flexible diaphragm from its original unflexed position, and fluid injecting means are connected to the fluid conduit for injecting fluid into the second chamber until the diaphragm is displaced toward its original position against the pressure of the fluid in the first chamber. The pressures of the fluids within the two chambers are then equal, and the pressure-measuring gauge will indirectly measure the pressure of the fluid within the first chamber.

A new method of absolute high pressure determination

Abstract: This is a preliminary description of a new method of determining absolute pressure which is based on the simultaneous measurement of length and ultrasonic transit times. This method has been used to determine the transition pressure of pure mercury at 0 °C at 75712±16 bar. It is particularly advantageous to use for calibrating secondary gauges such as manganin gauges inasmuch as it gives a highly accurate measurement of nonlinearities in such secondary gauges. The gauge calibrated in the present study reaches a maximum deviation from linearity of −116 bar at a pressure midway between atmospheric pressure and the 0 °C mercury melting pressure.

Surface pressure fluctuations in hypersonic turbulent boundary layers.

Abstract: The surface pressure fluctuations on a flat plate model at hypersonic Mach numbers of 5.2, 7.4 and 10.4 with an attached turbulent boundary layer were measured using flush mounted small piezoelectric sensors. A high frequency resolution of the pressure field was achieved using specially designed small piezoelectric sensors that had a good frequency response well above 300 KHz. The RMS pressures and non-dimensional energy spectra for all above Mach numbers are presented. The convective velocities, obtained from space time correlation considerations are equal to 0.7 U sub infinity. The results indicate the RMS pressures vary from 5 to 25 percent of the mean static pressures. The ratios of RMS pressure to dynamic pressure are less than the universally accepted subsonic value of 6 x 10/3. The ratio decreases in value as the Mach number or the dynamic pressure is increased. The ratio of RMS pressure to wall shear for Mach number 7.4 satisfies one smaller than or equal to p/tau sub w smaller than or equal to three.

Strain gauge transducer signal conditioning circuitry

Abstract: The disclosure describes circuitry for obtaining a pressure measurement from two strain gauge resistors mounted on a diaphragm which moves in response to changes in pressure. Operational amplifiers produce constant current flow through the resistors. A difference amplifier produces a measurement voltage corresponding to the difference in voltage across the resistors due to pressure variations. A unique positive feedback circuit is used in connection with the operational amplifiers to linearize the measurement voltage with respect to pressure changes. Temperature correction circuitry is used to maintain a constant measurement voltage scale over a wide range of temperature.

Investigation of the Sensitivity of Ionization-Type Vacuum Gauges

Abstract: A quantitative analysis of a large and representative sample of available data has been made to determine the best criteria for predicting the relative sensitivities of ionization-type vacuum gauges to different gases. The molecular property of the gas that correlates best with relative sensitivity is the ionization cross section σ (eV). The best σ value to choose according to gauge type is as follows: 1. For high-pressure ionization gauges, a σ evaluated at 23 of the accelerating potential of the gauge is the best choice. 2. For Bayard-Alpert and triode gauges, any of three choices are of approximately equal value. These are 100 eV σ values, maximum σ value for each gas, and a σ evaluated at 23 of the accelerating potential for each gauge. 3. For the Alphatron gauge, σ values in the range 5000–10 000 eV provide the best correlation. 4. For cold cathode ionization gauges, insufficient data were available to come to any conclusions.

Indirect measurement of systolic blood pressure in the lower limb using a mercury in rubber strain gauge

Abstract: The systolic blood pressure in the thigh, calf, and first toe was measured in 30 normal subjects between the ages of 13 and 55, using a mercury in rubber strain gauge on the toe as the indicator of systolic pressure. The thigh and calf systolic pressures were on average 2·8 mm Hg (SD± 12·8) and 5·2 mm Hg (SD± 12·2), respectively, above that of the brachial artery measured by auscultation. The mean toe systolic pressure was 5·1 mm Hg (SD ± 14·7) below that of the arm when allowances were made for the hydrostatic pressure effect caused by the difference in height between the arm and toe. After correction for changes in arm systolic pressure which occurred between the measurements, the elevation in thigh and calf systolic pressure over the arm was greatest in the older subjects. However, the drop in toe systolic pressure below that of the arm was most marked in the younger subjects. Pressure gradients have been calculated between the thigh and calf and between the calf and toe. The thigh systolic pressure is on average 2·4 mm Hg below that of the calf. The mean calf systolic pressure is 10·4 mm Hg above that of the toe. We conclude that the mercury in rubber strain gauge on the toe is an accurate measurement of systolic blood pressure in the lower limb, is extremely simple to perform, and will be of value in detecting systolic pressure gradients. The pressure measurements may be used to predict run-off problems before surgery for peripheral arterial disease and for selecting more accurately those patients with critical ischaemia.

Permeable membrane gas saturometer

Abstract: The saturometer measures the total dissolved gas pressure present in solutions such as in rivers, lakes, and other water bodies. A di-methyl silicone rubber tubing, permeable to gases and water vapor, is immersed in the water and a precision pressure gauge coupled to the tubing measures the internal pressures produced by gas components diffusing into the bore through the membrane wall.

Atmosphere Explorer pressure measurements: Ion gauge and capacitance manometer

Abstract: : Absolute pressure measurements are made by two instruments aboard Atmosphere Explorer: a cold cathode ion gauge and a capacitance manometer. The dual sensors feature (1) coverage from 120 km to 370 km with double coverage below 200 km; (2) differing and complementary sensing techniques; (3) usable output in the spinning and both normal and inverted despun satellite modes; (4) simple formatting to facilitate data use for real-time monitoring of spacecraft operation; and (5) cross-calibration in the laboratory and in space. (Author)

Pressure tester for injector sleeve of diesel engine head

Abstract: A pressure tester for a fuel injector sleeve installed in a diesel engine cylinder head. The pressure tester has at least one seal which isolates the portion of the cavity in the cylinder head in which the injector sleeve is disposed. An air passage admits compressed air through the pressure tester into the interior of the sleeve. A valve in the air passage locks the air under pressure within the sleeve cavity, and a pressure gauge communicating with the air passage inwardly of the valve detects any leakage past the injector sleeve when the valve is closed.

Microwave Breakdown of SF6

Abstract: Breakdown electric field strengths have been measured in four S-band cavities filled with high purity SF6 at room temperature in the approximate pressure range from 001 to 200 Torr Measurements were made for submicrosecond effective pulse widths under essentially `single pulse' conditions, and also under conditions equivalent to continuous wave breakdown The results are used to calculate an average elastic collision frequency of vc = 10 × 1010p sec-1

Apparatus for extruding plastic material

Abstract: The rate of feed of plastic material into a screw extruder is controlled in accordance with the internal pressure at at least one point along the extruder barrel by sampling the pressure measurement at one point in, or at each of several spaced points along, the extruder barrel at intervals under the control of a timing device driven by the extruder screw in such a way that each sample is taken from the same part of the pressure cycle Pressure samples are compared with a reference signal to produce an error signal when the value of one or more pressure samples deviates from a desired value These error signals, which may themselves be sampled under the control of the timing device to avoid hunting, are caused to adjust the rate of feed of material to the extruder, eg, from a second screw extruder, to restore the pressure to the desired value

A Base Pressure Experiment for Determining the Atmospheric Pressure Profile of Planets

Abstract: An experiment is described which consists of monitoring the base pressure of an entry probe and deriving the freestream pressure profile of a planet through correlation curves which directly relate base pressure to freestream pressure for the varying trajectory conditions. The experiment/technique is applicable for Mars, Venus, and Jupiter entry probes. The base pressure experiment offers distinct advantages to an entry probe mission such as a positive indication of where Mx = 1 occurs in the entry trajectory, a positive indication of boundary-layer transition onset, and a freestream pressure boundary condition at the A/x = 1.2 trajectory point independent of any other onboard or offboard measurements. The results of a recent slender cone R/V flight test have demonstrated the feasibility of the experiment by deriving the atmospheric pressure profile of Earth from base pressure measurements. Available flight and ground test base pressure data have been reviewed and an assessment made of which parameters are important to the base flow phenomena, which are well known and which require more investigaton to calibrate the experiment by obtaining additional data.

Absolute Length Measurement at High Pressure

Abstract: A length measurement system is described which can make absolute length change measurements of a meter long specimen within a pressure vessel (to pressures of 8 kilobar) with a fractional 3σ random error of ± 6 × 10−8 and a possible systematic error of less than 4 × 10−7 for changes in length of 1 cm. Possible uses of such a system for measuring the volume thermal expansivity (at pressure) and the isothermal bulk modulus (at pressure) are described. Moreover it is noted that when this system is combined with an ultrasonic velocity measurement system, the adiabatic bulk modulus (at pressure) and Gruneisen parameter as a function of pressure can be directly determined and the absolute pressure itself can be measured.

Pressure-inductance transducer

Abstract: In an electronic fuel injection system, a transducer for converting a variable pressure signal to a variable inductive signal has a coil wound on a plastic spool and surrounded by a ferrite cup and cap. A nickel plated steel sleeve snaps into the spool and supports a Teflon coated steel plunger which is tapered to provide a variable air gap with the ferrite cap. This assembly is resiliently supported in a housing and is operated through a bimetallic disc from an evacuated bellows responsive to the absolute pressure in the engine air induction passage. The bellows is positioned by a diaphragm which also is responsive to induction passage pressure to provide power enrichment. Adjustments are provided for the idle, power cut-in, and wide open throttle points and for initial calibration of the transducer.

Thermal Transpiration Error in Absolute Pressure Measurement with Capacitance Manometers

Abstract: Readings of two Baratron capacitance manometers with sensors at unequal temperatures, when compared over a wide range of pressures in helium and nitrogen, demonstrate appreciable nonlinearity caused by thermal transpiration. The asymptotic indication ratio at low pressure, 1.026±0.002, is approximately double the value reported by Bromberg, but considerably less than the Knudsen ratio for apertures. The data can be fitted to the Liang Equation, but the coefficients are sensitive to the geometry of the apparatus in the region of temperature transition.

High‐pressure calibration with a new absolute‐pressure gauge

Abstract: Based on the simultaneous measurement of length and transit time of a specimen under pressure, we have developed a new way of determining absolute high pressure. The mercury freezing point at 0 °C has been determined with this new method at 7571.2±1.6 bar. Accurate high‐pressure calibration of a secondary‐pressure gauge such as a manganin gauge is possible with this method. The maximum deviation from linearity of the present gauge studied is 11.6±0.1 bar between atmospheric pressure and the mercury freezing point at 0 °C.

Method and apparatus for measuring thin film absorption at laser wavelengths

Abstract: Absorption by thin film, such as an optical coating, of a selected laser wavelength is adapted to be measured by apparatus consisting of a thin test chamber whose diameter is at least several times its thickness. One wall of the chamber is a removable window, the opposite wall is reflective. A pressure measuring instrument, such as a capacitance microphone, is connected to measure the pressure of a gas in the chamber, and a laser having a selected test wavelength has its beam directed through the window into the chamber. The laser beam is chopped at an adjustable rate, and the pressure measuring instrument measures a pressure differential between a reference pressure chamber and the test chamber, there being an adjustable leak across the instrument. The test chamber is filled with a gas that does not absorb the test laser beam wavelength and the window is a material which preferably absorbs as little as possible of the wave-length of interest. The pressure in the chamber is first measured with the laser beam applied through the clear window to obtain the zero of the apparatus; any absorption of the laser wavelength by the window heats the gas by conduction and thus produces a pressure rise. Then a film to be tested is mounted in intimate contact with the inside surface of the window and the laser beam is applied through the film. Absorption of the beam wavelength by the film heats the gas and the window by conduction; when the heat of the gas and window reach a steady state the pressure of the gas in comparison with the ''''zero'''' pressure measurement is substantially proportional to the absorption of the film.

Inflation and pressure change indication device

Abstract: A combination device for inflating and deflating a pressurized container and for indicating variations from a predetermined pressure in the pressurized container. The device includes a first chamber exposed to pressure within the monitored container and a second chamber, or reference chamber, which is selectively pressurized to a predetermined reference pressure. A mechanism sensitive to a predetermined absolute pressure differential between the two chambers will simultaneously indicate the pressure change and will place the two chambers in fluid communication. Upon equalization of pressure between the two chambers, the mechanism may be returned to a position whereat it will cease to indicate and will block fluid communication between the two chambers. The device also includes an independent passageway for fluid communication between atmosphere and the pressurized container which is controlled by a normally closed inflation valve such as a standard tire inflation valve core.

Two phase pressure drop in inclined and vertical pipes

Abstract: A method of calculating the pressure drop in inclined and vertical oil-gas wells is proposed. The data used to establish the method is from a variety of sources but is largely from air and water flowing in systems close to one atmosphere in pressure and in pipes from 1 to 2 inches in diameter. All inclinations from vertical to almost horizontal are included. The method proposed is used to calculate the pressure distribution in ten oil and gas wells. The predictions for the overall pressure drop are good to + 10% for these wells.

Vibrating cylinder pressure transducer

Abstract: A vibrating cylinder pressure transducer has magnetic drive and pick up coils disposed in a non-magnetic cylindrical wall outside of the vibrating cylinder, all wires leading to and from the magnets being outside of the pressure chambers all together, whereby the interior of the vibrating cylinder is readily provided with a hermetic seal so as to provide an annular pressure chamber outside the vibrating cylinder, the inside of the vibrating cylinder being evacuated and the annular chamber being connected to a fluid source, the absolute pressure of which is to be measured In one embodiment, a three lobe (six node) vibration mode is rendered possible by providing electromagnets (either the drive pair or the sense pair) at an angle of 120* with respect to each other, the other pair being operated out of phase, diametrically opposite each other and along the bisector of the first pair

Deep sea pressure gauge

Abstract: A deep sea pressure gauge for measuring and recording pressure and temperature stably and accurately over long periods of time at the sea floor is provided. A fused quartz Bourdon tube pressure sensor and a quartz crystal oscillator temperature sensor provide high stability at low power. Only pressure variations from the sea floor pressure are measured, the mirror of the Bourdon tube rotating at a rate proportional to this pressure differential and controlling an angular position transducer having a frequency output. The pressure and temperature signals measured are average values covering the time between recordings. An argon-filled bag exposed to sea pressure is connected to the interior of the Bourdon tube to establish the initial, bottom pressure while the exterior of the Bourdon tube is exposed to oil which is maintained at ambient pressure by connection to an oil filled bag exposed to sea pressure.

Precision pressure gauge

Abstract: A force-balance, precision pressure gauge employing a fused quartz, helical, bourdon tube to transduce pressure into rotary motion, a fixed optical system to detect such rotary motion, and a force-balance system connected directly to the bourdon tube for rotation therewith to substantially limit such rotary motion.

An Ionization Gauge Using a Channel Electron Multiplier for Pressures Below 10−12 Torr

Abstract: A new ionization gauge of an estimated low pressure limit below 10−15 Torr and of a sensitivity of 2×109 Torr−1 is presented. The ions, which are produced in an ionizer of conventional design, are extracted through a shield aperture and collected by the funnel-type cathode of a channel electron multiplier. Since the high gain of this multiplier allows the gauge to be operated with an emission current of only several nanoamperes, practically no heat is produced in the gauge. The gauge is mounted on a 412-in. flange and has approximately the size of a normal Bayard-Alpert gauge. A general expression for the low pressure limit of hot filament ionization gauges is given. The results as obtained from this expression for gauges of similar geometry are discussed together with the low pressure limit as found for the new gauge.

Anti-backflow water control and solution proportioner

Abstract: A plurality of ventable chambers in tandem with a valve between them and disposed between a source of pressurized municipal water and a flow-control solution-proportioning device. The chambers have movable walls that close vents and open backflow check valves under conventional water pressures, and then open the vents and close the check valves while positive gauge pressure still exists in the water supply but which has dropped to a predetermined low positive gauge pressure or to a pressure inadequate to operate the proportioning device successfully. Resilient means are provided to control the wall movements and the venting and to predetermine the desired positive gauge pressure differential across the vents at which the respective openings and closings will occur.

Steam pressure cooker with safety device

Abstract: In a steam pressure cooker into which externally generated steam is introduced to build up a gauge pressure at which the cooking process is greatly accelerated. Safety means preventing the access door of the pressure vessel from being manually opened when the vessel is still under pressure and the steam admission valve from being opened when the door is not properly secured by the locking engagement of a latch.

Free-stream temperature, density, and pressure measurements in an expansion tube flow

Abstract: An experimental study was conducted to determine test-flow conditions in the Langley pilot model expansion tube. Measurements of temperature, density, wall pressure, pitot pressure, and shock and interface velocities were compared with theoretical calculations based on various models of the flow cycle. The vibrational temperature and integrated density of the molecular oxygen component of the flow were measured by use of vacuum ultraviolet absorption techniques. These measurements indicate both the presence and possible degree of nonequilibrium in the flow. Data are compared with several simplified models of the flow cycle, and data trends are discussed.