Showing papers on "Pressure measurement published in 1969"

Heat‐Pipe Oven: A New, Well‐Defined Metal Vapor Device for Spectroscopic Measurements

Abstract: A new, well‐defined metal vapor device called the heat‐pipe oven has been developed on the basis of the heat pipe, a heat conductive element designed by Grover and his co‐workers in Los Alamos. It continuously generates homogeneous vapors of well‐defined temperature, pressure, and optical path length. The vapor is confined by inert gas boundaries which remove the window problem and allow a direct pressure measurement without relying on vapor pressure curves. Due to the continuous evaporation and condensation the vapor purifies itself during operation.

Fundamentals of Temperature, Pressure, and Flow Measurements

Abstract: TEMPERATURE AND ITS MEASUREMENT. Early Attempts to Measure Degrees of Heat. The Air Thermometer. Thermodynamic Viewpoints of Temperature. The International Practical Temperature Scale. Liquid--in--Glass Thermometers. Resistance Thermometry. Thermoelectric Thermometry. Optical Pyrometry. Calibration of Temperature Sensors. Uncertainties and Statistics. Temperature Measurement in Moving Fluids. Installation Effects on Temperature Sensors. Transient Temperature Measurement. PRESSURE AND ITS MEASUREMENT. The Concepts of Pressure. Pressure Standards. Principles of Conventional Pressure Transducers. Pressure Measurement in Moving Fluids. Transient Pressure Measurement. FLOW AND ITS MEASUREMENT. The Concept of Flow Rate. Open--Channel Flow. Theoretical Rates in Closed--Channel Flow. The Discharge Coefficient. The Expansion Factor. Installations and Uncertainties. Answers to Problems. Solutions to Problems.

Highly Sensitive Capacitive Pressure Gauge

Abstract: Two capacitive pressure gauges which have been used extensively in the study of liquid and solid helium are described. The first gauge, constructed of Be–Cu, has a sensitivity of Δp∼2×10−6 atm for pressures of 100 atm. It is highly stable, has essentially no hysteresis, and is affected very little by changes in temperature below 4.2 K. The second gauge is of nylon construction and is suitable for NMR or with paramagnetic salt thermometry. A detailed description of the construction and use of both gauges is given.

Blood flow pressure measurement technique employing injected bubbled and ultrasonic frequency scanning

Abstract: A nonsurgical technique of measuring blood characteristics of pressure and flow by injecting minute gas bubbles into the bloodstream. The bubbles are subjected to a beam of ultrasonic radiation and flow is determined by detecting the resultant scattering which is indicative of the time taken for the bubble to pass between two points, while blood pressure is determined by varying the frequency of the ultrasonic beam to determine the resonant frequency of the bubbles which is proportional to pressure.

Some Precise Measurements of the Vapor Pressure of Water in the Range From 25 to 100 °C.

Abstract: The vapor pressure of water was measured at seven temperatures in the range from 25 to 100 °C using the boiler and precision manometer with which standard resistance thermometers were calibrated at the NBS in the 1940's. A table gives measured values of pressure, adjusted to even degrees, and indicates estimates of the standard deviations of pressure and of the corresponding temperatures. Except for the measurement at 25 °C, the values of pressure were consistent within one part in 50 000. The temperature measurements had an estimated standard deviation of 0.000 40 degree.

Venturi scrubber system including control of liquid flow responsive to gas flow rate

Abstract: In combination with a scrubber system which includes a venturi throat section for mixing a liquid with a laden gas stream, there are provided pressure measurement means in the flow path of the gas stream to provide a pressure drop measurement which shows an equivalent to pressure change across the venturi throat section. The system then effects, through differential pressure control means, an immediate change in liquid flow rate to such throat section responsive to the change in pressure drop such that a substantially constant pressure differential is maintained across the venturi and a resulting constant efficiency retained.

Pressure Calibration to 60 kbar Based on the Resistance Change of a Manganin Coil under Hydrostatic Pressure

Abstract: The relative resistance change of a properly seasoned manganin coil was measured at the center of the region of indifference for the bismuth II‐III, thallium II‐III, and barium I‐II phase transformations in a hydrostatic system. The equilibrium pressures for these transformations were obtained from the relative resistance change of manganin which was calibrated with pressure by means of the mercury L‐I and bismuth I‐II transition pressures. Equilibrium pressures corrected to 25°C of 26.861±0.042, 36.569±0.153, and 56.273±0.521 kbar were determined for the bismuth II‐III, thallium II‐III, and barium I‐II phase transformations, respectively. Only the barium I‐II point deviated from the presently accepted high pressure scale. On the basis of the manganin pressure gauge, either the presently accepted value of the barium I‐II point is too high by about 2.5 kbar or the pressure coefficient of manganin resistance changes sharply between 37 and 59 kbar. A two‐point quadratic calibration curve was satisfactory for pressures to 37 kbar.

The Transmission Characteristics of Large and Small Pressure Waves in the Abdominal vena Cava

Abstract: The mechanical behavior of the abdominal venae cavae of anesthetized dogs has been studied by measuring the speed, attenuation, and changes in waveform of various kinds of artificially induced pressure signals. The propagation of large amplitude pressure waves is shown to be affected by reflection interference and pronounced nonlinear phenomena. For pressure signals exceeding a few mmHg the speed increases with amplitude and the wave front steepens during propagation as in the early phases of the formation of a shock wave. By inducing distension waves in the form of finite trains of sine waves with amplitudes less than 20 mmH 2 O the dispersion and attenuation were determined without requiring Fourier transform computations. At transmural pressures between 50 and 300 mmH 2 O and frequencies between 20 and 100 Hz the vena cava was found to be only mildly dispersive and the logarithmic decrement appears to be independent of frequency. Irrespective of the amplitude and shape of the pressure signals, their speeds varied along the vena cava, and also with respiration. In addition, the speeds generally increased under the influence of the chemical and electrical stimuli applied, and with rising transmural pressure.

An Absolute Micromanometer Using Diamagnetic Levitation

Abstract: A friction-free suspension in vacuo is provided for a graphite disk by magnetic induction. The disk rotates round a vertical line of force inside a properly designed stator; when the stator is cooled, a thermomolecular torque is developed and the acceleration thus given to the disk is measured by an automatic device. It is shown that this acceleration depends only on the geometrical design of the manometer and on the pressure, to which it is proportional. The manometer unit is passive, very small, and insensitive to vibrations and shocks affecting the vacuum setup. The lower limit of its range of measurement is less than 10−10 Torr. When stator cooling is removed, the disk is influenced only by a (smaller) molecular damping torque. This depends on the composition of the residual atmosphere; provided this is known, the magnitude of the damping can be computed a priori with good precision so that the instrument becomes a useful standard manometer for calibration in the 10−3 to 10−7 Torr range.

Control systems for mining equipment

Abstract: THE SPECIFICATION DESCRIBES A HYDRAULIC-PNEUMATIC ANALOG TRANSDUCER FOR PROVIDING A PNEUMATIC PRESSURE INDICATION OF THE HYDRAULIC PRESSURE EXISTING IN A HYDRAULIC RAM. THE TRANSDUCER MAKES USE OF A MEMBRANE OF WHICH ONE SIDE IS SUBJECTED TO THE HYDAULIC PRESSURE WHILE THE OTHER SIDE, IN ACCORDANCE WITH THE HYDRAULIC PRESSURE OBTAINING, VARIES IN ITS DISTANCE FROM THE END OF A TUBE. AIR IS CAUSED TO PASS BETWEEN THE RESULTING ANNULAR GAP BETWEEN THE END OF THE TUBE AND THE MEMBRANE AND THE RESULTING PRESSURE GRADIENT IS MEASURED BY MEANS OF A PENUMATIC PRESSURE GAUGE.

Accurate Pressure Measurements in the Region 0.1–1000 mTorr; The Intercalibration of Two McLeod Gauges and a Capacitance Manometer

Abstract: The capacitance manometer appears to be a convenient and reliable pressure measuring device over the range 0.1–1000 mTorr. We find that deviations from linearity in this region do not exceed a few tenths of a percent. On the other hand, mercury streaming in a trapped McLeod gauge can introduce errors in the measured pressures which are dependent upon the pressure in a complicated manner.

Fluid operable motor

Abstract: A fluid operable motor element made of a tube of elastic deformable material (e.g. rubber) closed at one end. The tube is restrained against deformation transverse to its longitudinal axis, and against longitudinal deformation in a limited region of its side walls. The remainder of the sidewalls is free to execute elastic deformation in the longitudinal direction. When fluid pressure in the tube is changed to a pressure different from the ambient pressure, the tube flexes about the longitudinallyrestrained region of its sidewalls. Methods of making the motor element, several forms of it, and combinations of such motor elements with other devices and with other motor elements to form a pressure gauge, a clamping device, pliers, wrenches, a selfwrapping hook, and an artificial human hand, are described.

Apparatus for measuring tire pressures

Abstract: A pressure gauge for communication with the air in a tire including a graduated circular scale rotatable with respect to a pointer in response to the pressure in the tire. The pointer is operatively connected to a galvanometer controlled by a circuit having two thermistors responsive to the temperatures of the air in the tire and the ambient air respectively.

Wide range dynamic pressure sensor

Abstract: A DYNAMIC PRESSURE SENSOR OF THE TYPE WHEREIN A DIAPHRAGM IS PROVIDED IN A CAVITY WITH A DRIVING PLATE ON ONE SIDE OF THE DIAPHRAGM AND A SENSING PLATE ON THE OTHER SIDE OF THE DIAPHAGM WHEREIN THE DRIVING AND SENSING MEMBERS ARE PERFORATED AND SPACED FROM THE WALLS OF THE CAVITY SO THAT DAMPING AND APPARANT STIFFNESS INCREASE INDUCED BY INCREASED PRESSURE ARE REDUCED. BY REDUCING THE DAMPING AND APPARANT STIFFNESS, THE RANGE OF THE INSTRUMENT IS GREATLY INCREASED SO THAT IT CAN BE USED FOR MEASURING HIGH AND LOW PRESSURES.

Calibration to High Precision in the Medium Vacuum Range with Stable Environments and Micromanometer

Abstract: Ultrastable vacuum environments are combined with a micrometer-point contact manometer to obtain a calibration uncertainty of 1.2×10−4 Torr + 6 parts in 105 of the reading for the range 1×10−4 Torr to several Torr. The stable pressures are generated with a dynamic vacuum system and a servo control loop which employs cascaded error signals from a capacitance-diaphragm gauge to obtain pressure stabilities of better than ±1 part in 105 at 1 Torr. Precise evaluation of systems and procedures is given. Operational factors that affect accuracy were studied, for example, sorption in the manometer fluid, pressure distribution in the test chamber, time constants of the micromanometer, and thermal response of the control loop.

Experimental studies in magneto-fluid dynamics: flow over a sphere with a cylindrical afterbody

Abstract: The measured pressure distributions over the front hemisphere of a hemispherecylinder combination placed in an aligned fields magneto-fluid dynamic flow are presented. Integration of the pressure profiles show that the form or pressure drag of the composite body first increases as the magnetic field strength increases, at a fixed flow velocity, but then decreases as the magnetic field becomes still stronger.

Apparatus and process for the measurement of the pressure of corrosive material

Abstract: Apparatus for subjecting a corrosive material to a controlled pressure comprises a pressure vessel and a pressure measurement chamber, separated by a flexible diaphragm, which keeps the corrosive material within the pressure vessel, yet allows pressure to be transmitted to the pressure measurement chamber for measurement. Two methods of maintaining the flexible diaphragm in a pressure-transmissive position are described.

Correction for temperature loading and high gas pressure effects for the constant-temperature hot-wire anemometer

Abstract: An improved method of calculating the calibration curve for the constanttemperature hot-wire anemometer operating with high wire temperatures is described. Experimental results at high pressure and gas temperature conditions are also included.

Single-channel pressure telemetry unit.

Abstract: Single channel pressure telemetry unit for chronic implantation into cardiac chambers or major blood vessels in unrestrained animals for measuring ventricular pressure

Hydrostatic testing apparatus

Abstract: Portable apparatus for hydrostatically testing hydraulic equipment such as hydraulic-electric and air-over-oil car, truck and bus lifts, hydraulic dock leveling devices, hydraulic docks, and the like, to ensure its safe functioning and for preventative maintenance The apparatus includes a reservoir for hydraulic fluid, supply means for supplying hydraulic fluid under pressure to the equipment being tested, a pressure gauge assembly including a fitting for connection to the equipment being tested and a pressure gauge in communication with the fitting for registering the pressure in the equipment, and valve means for isolating the gauge and the fitting from the supply means

Electromagnetic effect on flow behind gaseous detonations.

Abstract: Flow behind propagating gaseous detonation waves is studied to determine how energy addition and momentum change brought about by the application of electromagnetic fields will affect such properties as pressure, temperature, and particle velocity. The analysis is based on a one-dimensional nonsteady model for the flowfield, coupled to a one-dimensional quasi-steady model for the wavefront. Results of numerical solutions are presented for 1) uniform electric and magnetic fields and uniform conductivity, and 2) varying electric fields with uniform magnetic fields and varying conductivity (calculated from measured field quantities), with positive and negative Lorentz forces in each case. Experimental pressure measurements are used to show that the theoretical predictions are qualitatively correct. Pressure increases of as much as 20% were observed downstream of the electromagnetic field when the Lorentz forces were pushing the flow, with no pressure change upstream of the field. Pressure increases of as much as 20% were observed upstream of the electromagnetic field when the Lorentz forces were retarding the flow, with pressure decreasing downstream of the field.

Pressure gauge assembly

Abstract: A pressure gauge assembly for gauging and having an open-fronted casing connectable through check valving to one or more pressure lines, the valving being front-ported for receiving and normally held open by a plug inserted in each such port, the gauge of the assembly being so connected to the casing as to be removable therefrom only after removal of the one or more plugs and consequent closing of the check valving without either dismounting or uncoupling the casing from any pressure line.

On an Apparatus for Tensile Testing under High Hydrostatic Pressure

Abstract: An apparatus for tensile testing of metallic materials under constant high hydrostatic pressure up to 15000kg/cmcm2 has been designed and constructed. This apparatus is so devised that during the tensile test two plungers each of diameter of 30mm are fixed in a high pressure cylinder, held fast together so as to keep the pressure inside the cylinder constant, and that the specimen which is attached to the lower plunger will be pulled by the shift of position of the cylinder to these plungers. The fluctuation in pressure during the test is so small that it is not detectable by the ordinary manganin pressure gauge. The change of the pressure is workable during the test, in case it is desirable by using a couple of Bridgman type tensile yokes and making the lower plunger, which is released of the specimen, shift its position by itself. In this case the fluctuation in pressure increases, but it remains within 100kg/cmcm2. The load is measured by a magnetostrictive load cell set in the high pressure chamber, The ongation of the specimen is obtained by measuring the movement of the cylinder. The dimension of the specimen is 3-5mm in diameter and 30-40mm in gauge length. The maximum load applicable to the specimen is 1000kg.

A Constant Current Source for Manganin Gauge Transducers

Abstract: The piezoresistive property of manganin has previously been exploited in producing a pressure gauge for shock wave studies. This article describes a constant current supply for the manganin gauge that utilizes an inductor as the essential constant current component. It is shown that the assumption of constant current can be made with negligible error. A termination technique is described which eliminates the gauge shunting current and hence simplifies data reduction.

An optical interference manometer

Abstract: This paper describes a simple multichannel manometer for aerodynamic and gas-dynamic measurements. The instrument makes use of optical interferometric techniques, using a laser light source. The output of the manometer is in the form of a photographic record of an interference fringe pattern, from which variations of pressure with time may be deduced. The sensitivity of the manometer remains constant over a wide pressure range. The response of the instrument is considerably faster than that of a liquid manometer or mechanical pressure gauge, and approaches that of a conventional pressure transducer. The main factors limiting the response are discussed.