The functions of the National Bureau of Standards are set forth in the Act of Congress, March 3, 1901, as amended by Congress in Public Law 619, 1950* These include the development and maintenance of the national standards of measurement and the provision of means and methods for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials, devices, ana structures; advisory services to government agencies on scientific and technical problems; in vention and development of devices to serve special needs of the Government; and the development of standard practices, codes, and specifications. The work includes basic and applied research, development, engineering, instrumentation, testing, evaluation, calibration services, and various consultation and information services. Research projects are also performed for other government agencies when the work relates to and supplements the basic program of the Bureau or when the Bureau's unique competence is required* The scope of activities is suggested by the listing of divisions and sections on the inside of the back cover. PublicationsThe results of the Bureau's work take the form of either ^ctual equipment and devices or pub lished papers. These papers appear either in the Bureau's own series of publications or in the journals of professional and scientific societies. The Bureau itself publishes three periodicals available from the Government Printing Office: The Journal of Research, published in four separate sections, presents complete scientific and technical papers; the Technical News Bulletin presents summary and pre liminary reports on work in progressJ and Basic Radio Propagation Predictions provides data for determining the best frequencies to use for radio communications throughout the world. ForewordPreparation of this Monograph on mercury barometers and manometers was undertaken to fill the need of manufacturers and users for information which is now scattered through the literature and in some cases unpublished. This information is primarily on the sources of error and methods for their correction. Moderately extensive tables of corrections for temperature, gravity, capillarity, and other errors are included, mainly for application to portable instruments. The various types of instruments are defined and design features affecting the accuracy discussed in some detail.The preparation of this monograph is part of the work on pressure stand ards now in progress in the Mechanics Division, B. L. Wilson, Chief, under the direct supervision of E. C. Lloyd, Chief of the Mechanical Instruments Section.A. V. ASTIN, Director. in The various designs of mercury barometers and manometers are briefly described, with a more extended discussion of the various design elements which may affect the achievable accuracy. Sources of error in measuring pressures are described in considerable detail, par ticularly for portable instruments, including scale...
Contents 1. 4.3.2. Deflection not amplified 20 4.3.3. Force balance systems 21 4.4. Optical transducer 21 4.4.1. Light beam transducer 21 4.4.2. Interferometric 23 4.4.3 Photoelectric 24 4.5 Capacitance transducer 24 4.5.1.Theory 24 4.5.2. Electrodes and pressure-sensitive elements 26 4.5.3. Measurement circuits 26 4.5.3.1. Capacity bridge balanced, change in capacitance measured 27 4.5.3.2. Capacity bridge unbalanced 27 4.5.3.2.1. Current measured 27 4.5.3.2.2. Voltage measured 27 4.5.3.3. Resonant capacity circuit, resonance maintained 28 4.5.3.3.1. Capacitance measured .-28 4.5.3.3.2. Frequency change measured 28 4.5.3.3.3. Beat frequency measured 28 4.5.3.4. Resonant capacity circuit; unbalanced current measured 28 4.5.3.5. Electic element null restored 29 4.5.3.5.1. Electrostatic voltage restores null 29 4.5.3.5.2. Pressure restores null -30 4.5.3.5.3. Spring force restores null 30 4.5.4. Performance factors 31 4.5.4.1. Sensitivity, linearity, and stability 31 4.5.4.2. Temperature effect 4.5.4.3. Gas composition 32 4.5.4.4. Gas adsorption 32 4.5.4.5. Ionization of gases 32 4.5.4.6. Variation of null with pressure 32 4.5.4.7. Stray capacitances 32 4.5.4.8. Overpressure 32 4.6. Inductance transducers 33 4.6.1. Differential transformer transducer 33 4.6.2. Mutual inductance transducer _ 33 4.6.3. Variable reluctance transducer 34 4.7. Strain gage transducers 4.7.1. Unbonded strain gage micromanometers 4.7.2. Bonded strain gage micromanometers 4.8. Electrical conductance manometer 4.9. Microwave null detector 4.10. Vacuum tube transducer . _ 4.11. Microphone micromanometers 4.12. Vibrating wire gage 5. Piston gages 5.1. Tilted, air-lubricated piston gages 5.2. Vertical piston gages 5.3. Piston-type pressure amplifier 6.
The National Bureau of Standards is engaged in fundamental and applied research in physics, chemistry, mathematics, and engineering. Projects are conducted in fifteen fields: electricity and electronics, optics and metrology, heat and power, atomic and radiation physics, chemistry, mechanics, organic and fibrous materials, metallurgy, mineral products, building technology, applied mathematics, data processing sys¬ tems, cryogenic engineering, radio propagation, and radio standards. The Bureau has custody of the national standards of measurement and conducts research leading to the improvement of scientific and engineering standards and of techniques and methods of measurement. Testing methods and instruments are developed; physical constants and properties of materials are determined; and technical processes are investigated.
A sensitive diaphragm capsule has been designed in which the two corrugated diaphragms nest into each other at external air pressures above a desired value. Evacuated capsules of this type have particular application in measuring pressure with radio sondes of the Diamond-Hinman-Dunmore type, where the deflection of the contact arm is fixed. At the ground level the diaphragms are designed to nest into each other and deflection does not begin until the air pressure is reduced to the value called the cut-off pressure. Several elements of two capsules each were constructed .with a cut-off pressure of 140 millibars. When installed in a radio sonde in place of the usual t ype, which is responsive over the entire range of pressures, a sevenfold increase in sensitivity in pressure measurement was obtained at altitudes above 46,000 feet.In measuring air pressure with radio sondes of the DiamondHinman-Dunmore type, l where the motion of the pressure contactor is a fixed distance, it IS desirable, in some cases, to increase the sensitivity at high altitudes. To secure this increase in sensitivity, a disphragm capsule has been des~ned at the National Bureau of Standards, the two diaphragms of whIch, when evacuated and sealed off in accordance with the usual practice for capsules used to measure atmospheric pressure, nest into each other at air pressures greater than a selected value. At pressures less than this cut-off value, the capsule deflects normally. The nesting of the diaphragms prevents damage to the relatively sensitive diaphragms, which might be caused by excessive differential pressures. The new diaphragm element is designed so that the contact arm of the radio sonde deflects over the same distance for the pressure interval from the cut-off to zero pressures, as does the ordinary element from sea level to zero pressures.The capsule, at zero pressure, is shown diagrammatically in figure 1. The connections needed for evacuating the capsule and for attachment to the radio sonde are not shown in figure 1. It is apparent from the form of the capsule that, as the air is evacuated from its interior, it will gradually collapse and finally, at a definite differential pressure, the two diaphragms will nest into each other and remain nested for larger external pressures. The evacuated capsule starts deflecting when the air pressure is reduced to a pressure equal to the differential pressure at which nesting took place during evacuation. This is known as the cut-off pressure.A pressure element of this type, consisting of two diaphragm capsules installed in a Diamond-Hinman-Dunmore radio sonde made by I Harry Diamond, Wilbur S. Hinman.Ir., Bnd Francis W. Dunmore, A method/or the inot8tigatiMI o/upper· air phenomena and it. application to radio meteorographl/.
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