Search

For the benefit of those who may wish to use vacuum tubes in meeting specific problems in the field of measurement, the comprehensive bibliography contained in this paper has been prepared. Some 600 references are included in this list, selected from a total of about 1,500 papers or books published since approximately 1920. The first portion of the bibliography contains publications dealing with the characteristics of vacuum tubes, and the second portion contains references to specific applications to measurement problems.

Since the publication of the above paper in the December, 1930, number of the Proceedings of the IRE, the attention of the authors has been called to two articles on the alternating-current resistance of solenoidal coils, by S. Butterworth, which they regret to state were overlooked in the preparation of the original paper. In the first of these articles (Phys. Rev., 11, 752-755; June, 1924) Butterworth has explained the disagreement of results, calculated by a formula derived by him in 1921, and the experimental results of Hickman (US Bureau of Standards Scientific Paper No. 472) as being due to a misinterpretation by the latter of the scope of this formula. The measurements of Hickman were carried out with long coils, while the constants in the formula cited apply only to coils whose length is less than their diameter. Butterworth shows that, properly extended, his formula correctly represents Hickman's experimental values of the resistance ratio. In the second of these articles Butterworth gives the derivation of this extended expression, formula together with that of two other formulas. In conclusion, the general agreement of the above-named paper's measured values and the values of resistance ratio computed by Butterworth's formulas may be regarded as satisfactory in all cases where the assumptions of the formulas are fulfilled. For a more rigid comparison, measurements are necessary with coils of more open winding and with greater attention paid to obtaining uniformity of spacing over the length of the coil.

In an important paper read before the June 1918 Convention of the A. I. E. E., it was shown by Mr. C. L. Fortescue, that any dissymmetrical system of three-phase voltages or currents could be resolved, by vector methods, into a pair of symmetrical systems, one forward and the other backward. The numerical ratio of the latter to the former is called the unbalance factor of the system. Although several vector methods were developed in the paper and its discussion, for evaluating the forward and backward components when the dissymmetrical triangle is given, so far as is known to the writer, no scalar and purely numerical method of developing them has been published. As it is useful sometimes to compute the two components without recourse to vector methods or to the drawing board, a numerical method is here offered.

It was shown by Bryan and Baker (5) that the coincidence method is one of the most accurate of visual methods of measurement. Their observations applied to sharply defined lines of various types. I have found that nearly the same degree of accuracy is obtained when the lines set into coincidence are not sharp, but have blurred edges, like those of absorption or interference bands. The reason for blurred lines being set into coincidence with nearly the same accuracy as sharp ones is to be described in detail elsewhere, with the various physiological factors on which accuracy depends. The method of coincidences has been applied both to direct visual measurements of absorption bands and also in a few cases to photographic records of such bands. In this paper the method of direct visual observation will be considered alone, because more experience has been gained in this connection. It is possible that in future the application to photography will prove the more important because the method would seem to be applicable to such cases as stellar and mass spectra photography.

This paper describes an experimental arrangement to determine the distributions of current and density of charge along cylindrical antennas. Using a wavelength of 1.90 meters, the distributions are determined for center-fed straight cylindrical antennas of a diameter of 29 mm, and lengths of 1.25 λ, 1.00 λ, 0.50 λ. For the first two cases, the measurements are repeated when a center self-tuned parasitic antenna, of the same length and diameter as the driven antenna, is situated at a distance of 0.30 λ and 0.15 λ. The distributions are determined also on the parasite. To test the accuracy of the measurements and to relate the relative values of the current with the relative values of the density of charge, the distributions are determined on a coaxial line, having the inner conductor of the same diameter as the antenna under experiment, and fed at the same frequency as the antenna. A few comparisons with theoretical results are made.

This paper represents a brief graphical-analytical exposition, followed by a mathematical development of the harmonics due to slot openings These were proved to be even and odd multiples of the number of slots plus and minus one. The modifications upon the torque speed curves of these harmonics have been discussed. A simple Fourier analysis underlies the whole phenomena.

A comprehensive device for the electronic measurement of the distribution of electrons in both electron micrographs and diffraction patterns is described. Electrons are detected individually while the image or pattern is scanned across the fixed electron detector, and the resulting information is displayed by a storage oscilloscope and recorded by a chart recorder or punched paper tape. Provision is made to select the energy of the electrons passed to the detector, allowing pictures to be obtained at a given energy level or the energy loss spectrum of a specimen to be examined. Representative results are given.

In this paper, we show that a restricted form of time travel both accords with special relativity kinematics and avoids several prima facie objections. We argue that such time travel provides a reasonable way to interpret certain phenomena which can readily be described, and the analogues of which have already been observed at the level of elementary particle reactions. We then describe how a time-traveling object could measure itself, and demonstrate how, in the appropriate circumstances, such an experiment could convince a theorist who insisted on a single criterion for length measurements that his standard had itself changed in length. The same experiment can shed light on the possibility of detecting a universal expansion; and we show that, given certain experimental results, one must conclude that every member of a class of time travelers has changed in length simultaneously, though perhaps only while going backwards in time.

In considering automatic techniques, many and varied definitions of greatly overused and misused words are applied. Certainly ``automatic,'' ``machine,'' and ``control'' are out in front in so far as repetition is concerned. In order to chart a course through the material to be presented in this paper, I will arbitrarily consider that automatic machine control is a condition whereby material is manufactured by a piece of machinery, with suitable equipment to measure the product while it is being manufactured and provide corrections to the machine itself to produce material within desired limits. The gages in this configuration of measuring equipment will be dimensional measuring devices indicating diameter, length, thickness, and so on.

The problem of evaluating dielectric constant and loss tangent by the short-circuited-waveguide technique has been encountered continually in recent years in the study of artificial dielectric media and radome materials. In general, practical measurements have involved materials with low loss and dielectric constants less than 10. The analytical method normally applied to data on such materials requires laborious computation. The available graphical methods have not completely eliminated computation and have provided answers of unsatisfactory accuracy. The present paper describes rapid graphical techniques for evaluating dielectric constant and loss tangent from the quantities normally measured with the slotted line, using samples of arbitrarily chosen length. It begins with equations previously derived for the case of low-loss media. By use of a new parameter, the relationship between dielectric constant and the measured shift in standing-wave minimum is plotted in such a way that all possible values of dielectric constant within any predetermined range are read directly from the graph with no computation whatsoever. A graph can be readily prepared to apply over a full range of frequency to all sizes of rectangular waveguide.

The NPL calculable cross capacitor is designed to provide a standard of the highest accuracy. It has a vertical axis and the length is determined by central guard tubes. The length is altered by axial displacement of the lower tube and the change is measured interferometrically. This paper describes the construction and performance of the capacitor and records the results of the initial measurements; the uncertainty of these is of the order of 10-7.

Where distribution systems serve areas of nonuniform load density, the usual criterion of kva (kilovolt-amperes) per square mile does not lend itself to an examination of circuit adequacy or system economics per loss considerations. An attempt is made in this paper to develop methods, suitable for planning purposes, which are based on the linear aspects of load distribution and by which the need and usefulness of alternate methods of distribution-system reinforcement can be evaluated.

Lasers can now be regarded as practical and economic tools with unique properties which have been utilized effectively in several applications in industry. Major applications of the laser are in thermal processes and measurements. Large amounts of concentrated energy allow microdrilling, welding, cutting, and fracturing to be simply effected in even the hardest materials. The coherence properties provide ideal sources for alignment instruments and interferometers for accurate length measurement. This paper describes these applications and their typical capabilities. Future developments and their potential are discussed, with the conclusion that the laser will be increasingly used in the manufacturing environment.

Various factors contribute to impair the quality of telegraph signals. For instance, there may be interfering currents either induced in the circuit or brought in by conduction, the proportioning of the circuit elements may be imperfect or batteries and relays may be out of adjustment. The result in any case is to distort the telegraph signals so that the received signals are not a true copy of those transmitted. The paper describes methods for measuring this distortion and for analyzing the results so as to indicate the nature and extent of the impairment and its probable cause.

The paper describes one method of establishing frequency standards employed by the Bureau of Standards which is based on the direct measurement, in linear measure, of the wave length of very short standing waves on a pair of parallel wires. The wave lengths measured were from 9 to 16 meters, the currents having frequencies from 33,000 to 19,000 kilocycles per second. The apparatus for generating these ultra radio-frequency currents is described, as well as the details of the method used in measuring the wave length of the waves which they produce on the parallel wires. A method is described for calibrating a wavemeter at frequencies from 30,000 kilocycles to 352 kilocycles (10 to 850 meters). This method makes use of the harmonics in a second radio-frequency generating set, one of which, when combined with the output from the ultra radio-frequency generating set, produces a beat note in a receiving set tuned to the ultra radio-frequency. The zero beat note method is used to obtain an exact setting. Knowing the frequency of the ultra radio-frequency generating set by direct measurement on the parallel wires, and the order of the different harmonics being used in the second radio-frequency generating set, the frequency of the latter may be determined over the range from 30,000 kilocycles to 352 kilocycles (10 to 850 meters).

This paper presents the results of investigations made to explain the wide differences found between dielectric loss measurements made on full reel lengths of cable and on samples (10-ft. net length) removed from these reels. At least one source of such differences is found in losses occurring at the end of the cable, these losses being insignificant in the case of the full reel but amounting ing to as much as 100 per cent of the loss in the normal sample. Methods of determining, controlling, and eliminating these end losses are described.

The comparison reflectometer is an instrument designed to locate and measure the characteristics of reflections in waveguide and transmission-line systems: it is particularly suitable for measuring small reflections in precise microwave measuring instruments up to one meter in length. It consists of a reflectometer in which the returning waves are combined with an accurately known reference wave and a measure of the total reflection coefficient is recorded automatically on punched paper tape at a number of preset frequencies covering a particular waveband. From sets of readings taken without, and with, the test component connected, a computer calculates and plots the distribution of reflections as a function of distance and prints out their magnitudes and phases. The reflection coefficients of individual discontinuities are also plotted by the computer as a function of frequency on Smith charts. Under suitable conditions point reflections may be Iocated in X-band waveguide within a few tenths of a millimeter and measured with an accuracy of /spl plusmn/3 percent in magnitude and /spl plusmn/ 5/spl deg/ in phase angle. The method compensates for imperfections in the reflectometer and so reduces the background level of spurious reflections to less than 0.00006.

This paper describes techniques for reducing errors encountered in measuring the amplitude of 100-300 kV pulses which are a few microseconds in length. The accuracy to which such measurements can be made depends, for the most part, on how precisely the behavior of the voltage dividing network is known. Problems due to stray reactances, temperature, voltage effects, dielectric and dimensional instabilities, losses, improper terminations, and external circuitry are dealt with, with particular emphasis on capacitive voltage dividers. Also described briefly are an ultrastable laboratory standard divider, calibration techniques, and measuring instrumentation.

The techniques analyzed in this paper are based on precision-measuring systems that exhibit resolutions of 0.0001 in reflection coefficient and accuracies of 0.05 percent in characteristic impedance over the 100 MHz to 8.5 GHz frequency range. In order to consider safely reflection coefficients as high as 0.1, multiple reflections are not neglected in the analysis. Subjects considered include 1) the separation of measuring-system residual reflections utilizing air-line standards of specified, arbitrary, and variable length, 2) the limits of accuracy resulting from imperfect air-line standards and multiple reflections, 3) the importance of connector repeatability, and 4) the advantages realized through the use of highly stable impedance-matching tuners.

This paper describes a simple method for the calculation of errors due to the finite length and separation of X-array hot-wire anemometers. Results of computations for a typical wire array are presented for total and spectral turbulence measurements. Although the actual errors are slightly underestimated due to the simplifying assumptions used to reduce the computational effort, it is found that the wire length and separation effect is very significant. The analysis does not require complete correlation or spectral functions of the flow and includes the effect of nonuniform wire sensitivity.

Softness of human hair plays a big roll on the manageability of it. Therefore, it is important to measure the softness quantitatively. It is well known that the softness of long shaped materials can be obtained from tensile young's modulus and bending modulus. The tensile young's modulus is most generally empolyed as a parameter of softness, but is usually obtained by destructive way. Bending elasticity can be obtained by nondestructive way and is suitable for the study of the natural materials with scattered properties such as hair. But accurate measurement on hair bending may be difficult because of its hygroscopy and curl, and there is little informations about the bending of hair within authors' knowledge. In this paper, the bending length measurement, which is one of the possible way to measure the bending elasticity, is applied to study the softness of hair. The increased bending length with the enviromental humidity is arised from the increase of the bending elasticity and that of the weight caused by the absorption of water, and the latter can be reduced by peirce's equation. The effect of curl can be minimized by the average of the bending length's of two opposite situations along the axis of the hair. As the result, the softness of hair is obtained with good accuracy by means of the bending length.

An improved model for short channel IGFETs representing inherent two-dimensional effects will be described. It features accuracy in both triode and saturation response, yet is simple enough for CAD applications.

The original paper of DeGrasse and subsequent publications dealing with the use of the crossed-strip gyromagnetic coupler as a limiter have been concerned with the operation of this device below 3300 Mc. At these frequencies the limiter exhibits a sharp threshold at a very low power level, in the neighborhood of -20 dbm. Fig. 1 illustrates typical flat leakage characteristics at a frequency of 2600 Mc. A single crystal YIG sphere of 26 mils was used in this limiter.

The paper presents what is believed to be a new theorem in electrostatics, showing that the direct capacitance of a very general type of cylindrical 3-terminal capacitor is a constant, namely (log? 2)/4?2. The presentation and proof of this theorem is followed by a detailed analysis of a cylindrical 3-terminal capacitor of rectangular cross-section, in which the effects of various practical limitations are evaluated in quantitative terms. The results of similar analyses of cylindrical 3-terminal capacitors of other cross-sections are stated. As a consequence of this work, it appears that such cylindrical 3-terminal capacitors are extremely attractive as precise calculable standards of capacitance, only one precision length measurement being necessary to enable their capacitance to be computed to a high order of accuracy.