Showing papers in "Review of Scientific Instruments in 1933"
202 citations
TL;DR: In this paper, a modified Soller's circuit for balancing out battery e.m.f. changes has been studied in detail and a modified circuit was developed in which the adjustments are less critical and which allows balancing out of changes in filament emission also.
Abstract: The sensitivity of d.c. amplifying circuits with FP‐54 tubes is limited by the stability which can be obtained. In single‐tube circuits it is necessary to balance out fluctuations caused by changes in battery e.m.f. and in filament emission. Soller's circuit for balancing out e.m.f. changes has been studied in detail and a modified circuit has been developed in which the adjustments are less critical and which allows balancing out of changes in filament emission also. The latter is accomplished by balancing the plate current against the current to the space‐charge grid. Details of construction and manipulation of the new circuit are given, as well as data on its stability.
95 citations
TL;DR: In this paper, a detailed technique for the measurement of the permeability of porous media, by the use of either liquids or gases, is described, and derived of the formulae by which the measurement may be computed from the laboratory measurements.
Abstract: A detailed technique is described for the measurement of the permeability of porous media, by the use of either liquids or gases. Derivations are given of the formulae by which the permeability may be computed from the laboratory measurements. In addition to defining a convenient permeability unit, it is proposed to call it the ``darcy.'' Field measurements on the effective permeability of underground sands are discussed, and the appropriate formulae are derived. These include expressions for liquid flow, gas flow, gravity flow and composite artesian and gravity flow. Correction curves are given for application when the wells do not completely penetrate the producing sands.
73 citations
TL;DR: In this paper, an electrostatic generating voltmeter is described which has a strictly linear scale and no commutators, and whose calibration is independent of the speed of the driving motor and of the characteristics of the associated vacuum tube amplifier.
Abstract: An electrostatic generating voltmeter is described which has a strictly linear scale, which has no commutators, and whose calibration is substantially independent of the speed of the driving motor and of the characteristics of the associated vacuum tube amplifier. A means of calibration by use of a wire grid in front of the voltmeter is also described.
28 citations
23 citations
TL;DR: A determination of the number of α-particles emitted per unit areas per unit time by materials usually used in the construction of ionization chambers has been made as mentioned in this paper, and methods of removing radioactive material from surfaces were investigated.
Abstract: A determination of the number of α‐particles emitted per unit areas per unit time by materials usually used in the construction of ionization chambers has been made. The radioactive contamination of a few gases was examined and methods of removing radioactive material from surfaces were investigated. A FP54 vacuum tube, operated at about one‐tenth of the maximum sensitivity, was used with a photographic recorder for detecting the α‐particles. With this sensitivity α‐particles of a range in air of 2 mm or more could be detected. Cold rolled steel which emitted about 3 α‐particles per 100 cm2 per hour was the freest from contamination of any material examined. Brass and copper were the next best materials. Careful sandpapering of a surface was very effective in removing radioactive material. It was also found that a clean surface when exposed to air became contaminated. This made it necessary to keep such surfaces in an atmosphere of nitrogen or some gas which was free from radioactive contamination. Celluloid which was cleaned with alcohol and painted with good drawing ink made a satisfactory material for ionization chamber windows. Amber emitted no more α‐particles than steel but Pyrex glass emitted about 5 times as many α‐particles as steel. Methyl bromide, good quality carbon dioxide, and nitrogen were found to be suitable gases for filling ionization chambers.
18 citations
TL;DR: Capacitance bridge measurements at audio-frequencies with a Weston Photronic cell at different illuminations yield data for such a graph. as discussed by the authors concluded that the impedance element itself is capacitative and maintains a constant phase difference between current and voltage.
Abstract: A general method of determining the equivalent circuit elements of a network containing any number and arrangement of resistances with one variable impedance element involves plotting a graph of the reactive component of the impedance against the resistive component at different frequencies. Capacitance bridge measurements at audio‐frequencies with a Weston Photronic cell at different illuminations yield data for such a graph. Circles are obtained from which it is concluded that the impedance element itself is capacitative and maintains a constant phase difference of the order of magnitude of 10° between current and voltage. The impedance of the cell as a whole decreases radically with frequency. From the circles it is found that the equivalent resistance in series with the impedance element is of the order of 35 ohms and is independent of illumination and other variable factors. The equivalent resistance in parallel with the impedance element is of the order of several thousand ohms, decreases with illum...
14 citations
TL;DR: A modification of Soller's balanced circuit for use of a single FP-54 tube has been found which gives improved stability of balance and the possibility of use with galvanometers of high resistance as mentioned in this paper.
Abstract: A modification of Soller's balanced circuit for use of a single FP‐54 tube has been found which gives improved stability of balance and the possibility of use with galvanometers of high resistance. The theory of the circuit and detailed directions for calculating, setting up, and balancing it are given.
13 citations
TL;DR: In this article, a new vacuum tube voltmeter with a response proportional to the logarithm of the input voltage is described, which is based on the distortion of the plate-current wave form occurring in a tube of the ''variablemu'' type.
Abstract: A new vacuum‐tube voltmeter which has a response proportional to the logarithm of the input voltage is described. The operation of the device is based upon the distortion of the plate‐current wave form occurring in a tube of the ``variable‐mu'' type, and upon the use of a diode rectifier to select only that portion of the wave which has been ``compressed'' by the curvature of the tube characteristic. The elementary circuit may be cascaded for extension of the range of input voltage over which the response is logarithmic. The speed of response of the device to changes in signal intensity is practically unlimited, and the frequency fidelity is only slightly inferior to that of a comparable impedance‐coupled amplifier designed for the same frequency band. Commercially available tubes are used throughout.
12 citations
12 citations
TL;DR: In this article, a sensitive and accurate method for measuring electromotive force through large resistances, up to around 100,000 megohms, was described for detecting electromotive forces in systems which are easily polarized.
Abstract: A sensitive and accurate method is described for measuring electromotive force through large resistances, up to around 100,000 megohms, or for measuring electromotive force in systems which are easily polarized The measuring instrument is simply and inexpensively constructed of standard parts which are readily available, and in actual use it is convenient, dependable and rugged
TL;DR: In this paper, a summary of the values obtained by various observers of the temperature coefficients of the modulus of rigidity and Young's modulus for the metals and alloys of possible usefulness in the construction of the elastic members of instruments is presented.
Abstract: A summary is presented of the values obtained by various observers of the temperature coefficients of the modulus of rigidity and Young's modulus of elasticity for the metals and alloys of possible usefulness in the construction of the elastic members of instruments. The composition of each material is given and also the condition of heat treatment or cold work. Much of the data is the result of recent work at the Bureau of Standards.
TL;DR: In this paper, the importance of constancy of the background ionization due to cosmic and local radiation is emphasized, and precautions are described which insure a highly constant background in the present type of apparatus.
Abstract: For the removal of radon from liquids, simplified apparatus, including a special reflux condenser, free from carry‐over difficulties, is described. For the measurement of small quantities of radon or thoron, cylindrical ionization chambers, with moisture proof insulation, together with a removable head, evacuated, bifilar electrometer are described. The importance of constancy of the background ionization due to cosmic and local radiation is emphasized, and precautions are described which insure a highly constant background in the present type of apparatus.
TL;DR: In this article, it was shown that a 10 percent change in the a.c. voltage caused from 0.1 to 0.02 percent increase in the voltage output of the filter.
Abstract: When triode vacuum tubes are used as rectifiers approximately constant d.c. voltage can be obtained from a rectifier‐filter circuit by having changes in the a.c. line voltage control the grid bias of the triode rectifiers. By using common radio receiving tubes in circuits which are described it is found that a 10 percent change in the a.c. voltage causes from 0.1 to 0.02 percent change in the d.c. voltage output of the filter.
TL;DR: In this paper, a grazing-incidence vacuum spectrograph for a twenty-one foot focal-length grating has been set up and adjusted, and very sharp lines have been obtained, and some spectrograms of copper are compared with others which were taken by a one-meter GIC spectrogram.
Abstract: A grazing‐incidence vacuum spectrograph for a twenty‐one foot focal‐length grating has been set up and adjusted. The angle of incidence is 79 degrees. The various adjustments on the instrument which enabled rapid focussing are described. Very sharp lines have been obtained, and some spectrograms of copper are compared with others which were taken by a one‐meter grazing‐incidence vacuum spectrograph. These definitely show the advantage of the large dispersion of the new instrument. Several groups of lines have been found which appear to be multiplets but as yet have not been classified. Work is being continued on Be, B, Al, Cu, Ni, Co and Zn.
TL;DR: In this paper, the dispersion data for rocksalt originally determined by Paschen were corrected to 25°C with the use of temperature coefficients derived from the measurements of Liebreich.
Abstract: The dispersion data for rocksalt originally determined by Paschen are corrected to 25°C with the use of temperature coefficients derived from the measurements of Liebreich. Values of the angle of minimum deviation of a 60° prism and the prism table angles from the sodium D lines for a spectrometer with the Wadsworth mounting of a 60° prism and plane mirror are calculated for 25°C. Tables are given with which corrections may be easily made for temperatures other than 25°C and for prism angles between 59 and 61°.
TL;DR: The spectrum interval sorter described by the writer has been considerably modified to increase its accuracy and convenience as mentioned in this paper, which greatly facilitates the use of such groups of lines, each group to contain not more than a limited number of lines given by their frequency density and the accuracy with which their frequencies are known.
Abstract: The spectrum interval sorter recently described by the writer has been considerably modified to increase its accuracy and convenience. Probability considerations of the relative numbers of real and accidental interval coincidences to be expected in typical complex spectra indicate the desirability of applying the combination principle to selected groups of lines, each group to contain not more than a limited number of lines given by their frequency density and by the accuracy with which their frequencies are known. The modified machine greatly facilitates the use of such groups of lines. Sprocket driven perforated paper tape replaces the plain tape previously used, which introduced errors due to mechanical stretching when intervals were recorded which involved a loop of tape greater than four meters in length. With the device in its present form intervals up to 10,000 wave numbers can be recorded with accuracy to ±0.02 wave number. A new system of tape calibration has been introduced, in which a separate ...
TL;DR: Based on observations of thermoelectric power and the Wiedemann-Franz ratio λ/κ, a compensated radiation thermopile was built and operated in a vacuum at low temperatures, which shows a more than tenfold increase in sensitivity when operated at the temperature of liquid oxygen, as compared to operation at 25°C.
Abstract: Based on observations of thermoelectric power and the Wiedemann‐Franz ratio λ/κ, a compensated radiation thermopile has been built and operated in a vacuum at low temperatures, which shows a more than tenfold increase in sensitivity when operated at the temperature of liquid oxygen, as compared to operation at 25°C.
TL;DR: The twenty-one foot normal incidence vacuum spectrograph as mentioned in this paper has been improved by the provision of 30,000 line per inch glass and speculum gratings in addition to the 15,000 lines per inch grating previously used, and by the installation of a simpler and much more rapid pumping system.
Abstract: The twenty‐one foot normal incidence vacuum spectrograph previously described by the writer has been improved by the provision of 30,000 line per inch glass and speculum gratings in addition to the 15,000 line per inch grating previously used, and by the installation of a simpler and much more rapid pumping system. The previous range of 2000 to 1000A has been extended so that the instrument can be used from 6000 to 300A, and orders up to and including the sixth have been photographed, giving dispersions ranging between 2.72A/mm and 0.22A/mm with the advantages of an almost normal spectrum. When a constant value for the dispersion is used over a 16 inch plate the correction factor seldom exceeds 0.3A. The errors introduced when Rowland's method of coincidences is used with these Wood gratings appear to be much less than 0.01A. Wave‐lengths of numerous lines of the hot‐spark spectra of copper and nickel, and of the high frequency discharge spectra of argon and neon, have been measured with the instrument, a...
TL;DR: In this article, a simple crystal growing apparatus is described which allows the production of very uniform single crystalline rods of low melting point metals, which may be produced in any desired gas atmosphere or in a vacuum.
Abstract: A simple crystal growing apparatus is described which allows the production of very uniform single crystalline rods of low melting point metals. The crystals may be produced in any desired gas atmosphere or in a vacuum. Any orientation of crystal to rod may be obtained by a simple seeding procedure.
TL;DR: In this article, three different circuits for use with a single vacuum tube in order to balance out effects of fluctuations of the emf of the plate battery are described, and the theory of the circuits is worked out and the expressions for the galvanometer current given.
Abstract: Three different circuits for use with a single vacuum tube in order to balance out effects of fluctuations of the emf of the plate battery are described The theory of the circuits is worked out and the expressions for the galvanometer current given The circuit in which the stability of balance depends upon the constancy of the amplification factor, μ, is found to be the most stable A modified two tube circuit operating on this principle is suggested
TL;DR: In this paper, a dummy tube is used in the plate circuit to obtain a resistance characteristic which makes it possible to attain the full amplification of 1500-2500 per stage for the ''57'' tube using only 300-600 volts plate supply.
Abstract: In order to utilize even 25 percent of the theoretical amplification factor of high mu tubes, it is necessary to use a plate load resistance and plate potential too high to be practical. By the use of a dummy tube in the plate circuit, however, one can obtain a resistance characteristic which makes it possible to attain the full amplification of 1500–2500 per stage for the ``57'' tube using only 300–600 volts plate supply. Output voltages as great as 450 volts are attainable with negligible distortion.
TL;DR: In this paper, a portable amplifier is described, and it shows that proper utilization of these characteristics has resulted in an amplifier practically free from the effects of A and B−battery drifts, and when used to amplify the current from a cadmium photocell, to measure ultraviolet radiation, its calibration was reproducible from day to day with an average deviation of less than 0.8 percent.
Abstract: Characteristic curves for various types of radiotrons are presented, together with a discussion of some of the characteristics desired. A portable amplifier is described, and it shows that proper utilization of these characteristics has resulted in an amplifier practically free from the effects of A and B‐battery drifts. It was found that when it was used to amplify the current from a cadmium photocell, to measure ultraviolet radiation, its calibration was reproducible from day to day with an average deviation of less than 0.8 percent.
TL;DR: In this paper, a method for removing radon from rocks and for measuring minute quantities of radon is presented, where powdered rock specimens are boiled without flux by direct heating in an evacuated, graphite-resistance furnace.
Abstract: New principles for removing radon from rocks and for measuring minute quantities of radon are presented. Powdered rock specimens are boiled without flux by direct heating in an evacuated, graphite‐resistance furnace. The duration of heating is 2½ minutes, which is to be compared with about one hour for the quickest of former methods. The gases from the melt are led to the ionization chamber through an electrostatic ion‐trap. A small insulation drying device in the ionization chamber protects the amber from water vapor. The natural observational limit for measurements of small quantities of radon is defined as the point at which the average ionization from the radon just equals the probable statistical variation in the background ionization due to cosmic and local radiation, and an apparatus is described which permits measuring radon down to this limit. A string electrometer measures only the difference in ionization in two identical ionization chambers, both of which contain the same background gases, but only one of which contains the radon to be measured. A systematic study of the percentage of the total radon removed from biotite granite as a function of (a) temperature, (b) duration of heating, (c) fineness of sample grains, showed that temperature is the only important factor, and that 1800°C effects complete radon removal.