86 research outputs found
Weston Station Voltmeter
No full textOne of the many electrical engineering machines from Weston Electrical Instrument Co. The company was founded by Edward Weston, in 1888, in Newark. Weston was an early competitor of Thomas Edison in electric light but then turned toward innovations in electrical measurement instruments, gaining prominence in scientific and engineering fields. He was also one of the founders of the Newark Technical School, which became NJIT. Weston Hall is named after him and his son, Edward Faraday Weston. In 2016, Weston’s meters were awarded an IEEE Milestone, the plaque for which is viewable inside the NJIT Electrical and Computer Engineering Department. This voltmeter is used for measuring volts, the differences of potential between points of an electrical circuit.https://digitalcommons.njit.edu/instruments/1025/thumbnail.jp
Direct-reading ammeter
No full textThis Weston ammeter, model 1, measures electrical current in amps. It was manufactured by the Weston Electrical Instrument Corporation of Newark, NJ. It was calibrated in 1912, before it began to be used, and was guaranteed accurate when used at 72 degrees Fahrenheit.https://digitalcommons.njit.edu/instruments/1073/thumbnail.jp
Direct current milliammeter
No full textThis Weston milliammeter measures current at a more sensitive range than the ammeter (a milliamp is one thousandth of an amp). This was the Weston Corp’s first model of milliammeter, produced between the 1910s and 1930s.https://digitalcommons.njit.edu/instruments/1071/thumbnail.jp
Weston Laboratory Standard Type No. 150 Millivoltmeter
No full textThis permanent magnet moving coil instrument was widely used as a reference standard of voltage or of current (with a suitable shunt) for the calibration of portable direct current (DC) instruments. The Brooks deflection potentiometer proved capable of greater accuracy and stability and such potentiometers superseded the laboratory standard type for DC measurements early in the 20th century.34 x 40 x 11 c
Weston electrical instruments for use on alternating-current switchboards : catalog 16.
No full textIncludes index.Mode of access: Internet
Weston Laboratory Standard Type No. 22 Wattmeter
No full textThis electrodynamic wattmeter is typical of the laboratory standard type of instrument manufactured about 1900 and used as reference standards for calibrating portable instruments used for measuring power in ac circuits. Such instruments were calibrated at the National Bureau of Standards against a Kelvin watt-balance and later against an astatic suspended coil electrodynamometer. The same current coil is used on all ranges but taps on the series resistor serve to change the range. It was purchased in 1905.19 x 24 x 27 cmno. 631
An investigation into solid dielectrics
No full textDirect measurement techniques for the investigation of electrical processes in solid dielectrics are reviewed and their respective strengths and weaknesses are discussed, particularly the complementary nature of thermally stimulated current measurements. The successful design and construction of a new Thermally Stimulated Discharge Current (TSDC) Spectrometer at the University of Southampton is presented and its correct function validated with experimental measurements of the well known and often characterized synthetic polymers low density polyethylene (LDPE) and polyethylene terephtalate (PET). Results were found to correspond well to published data. First TSDC observations of filled and oil impregnated papers are presented.The second aspect of this work is the investigation of natural polymer insulation materials,specifically paper for oil-paper insulation systems. For the first time, electrical insulation papers with filler contents up to 50% were investigated. Bentonite and talcum were compared as filler materials and found to have negative and positive effects respectively.The superior electrical strength of a talcum filled kraft paper was verified, and a series of constructive modifications was undertaken to further maximise its electrical strength at comparable or improved dielectric performance. An increase in electrical breakdown strength of 20% to 30% has been observed, but the substitution of such great amounts of fiber with fillers also lead to a reduction in mechanical strength of the paper. Further trials with chemical additives were conducted to counteract this effect and polyvinyl alcohol and starch were found to enhance the paper strength. Additional trials also comprised sizing agents, guar gum and wet strength agents. Uncharged or slightly charged chemical additives provided best results with regard to dielectric performance. The significance of the trialled paper modifications is judged in light of statistical analysis
Forest K. Harris
No full textFOREST K. HARRIS
NBS: 1925 ‑ 1971
Birth: August 26, 1902, Gibson County, Indiana
Death: November 3, 1991, McLean, Virginia
Education:
Oklahoma University degrees in physics: BA, 1921; MS, 1923
Johns Hopkins University, PhD (Physics), 1932
Principal field:
Precise electrical measurements and standards
Positions held at NBS:
Research Fellow for Munsell Color Company
Physicist, Electrical Instruments Section
Chief, Absolute Electrical Measurements Section
Post‑retirement: Consultant to the Electricity Division
Honors:
U.S. Department of Commerce Silver Medal, 1955
NBS Rosa Award, 1963
Institute of Electrical and Electronics Engineers Leeds Award, 1972
Instrument Society of America Award, 1973
National Conference of Standards Laboratories Wildhack Award, 1981
Elected to Phi Beta Kappa, Sigma Xi, and Sigma Tau
Memberships:
Institute of Electrical and Electronics Engineers (Fellow)
American National Standards Institute
Washington Academy of Sciences (Fellow)
Cosmos Club
Publications:
Author or co‑author of numerous publications, including a standard reference textbook: Electrical Measurements, Wiley, 1952; contributor to handbooks and encyclopedias; Associate Editor, Review of Scientific Instruments
Growth of single-wall carbon nanotubes by chemical vapor deposition for electrical devices
No full textCarbon emerges in di®erent forms. Diamond and graphite have been well known mate-
rials for centuries. Moreover fullerenes and nanotubes were discovered only a few years ago.
H. W. Kroto et al. depicted the fullerenes in 1985 [1]. A few years later, in 1991, S. Iijima
described carbon nanotubes (CNTs) for the ¯rst time [2] (Figure 1.1).
CNTs have a close relation to graphite, since a single-wall carbon nanotube is like a rolled-up
graphite mono layer. However a nanotube has with its curved shape a higher chemical reacti-
vity than a °at graphite layer. Both the side wall and the caps can be modi¯ed chemically [3].
Carbon nanotubes are regular carbon clusters with attractive mechanical and electronic pro-
perties [4]. Nanotubes have a high mechanical strength due to a very large Young's modu-
lus [5]. They can be used for the storage of hydrogen [5, 6], to store energy in electrochemical
double layer capacitors [7] or to reinforce composite materials [3]. A single nanotube can be
used as a sensor [8{12], a nanorelay [13], a vessel [14] or as a template [3, 15]. It is possible
to produce light bulbs [16] and ¯bers [17] with carbon nanotubes. An array of CNTs can act
as a °at panel display [3, 5] using their feature to act as ¯eld emitting devices [18{21].
CNTs are either metallic (1/3) or semiconducting (2/3). Nowadays it is not possible to select
the desired characteristic of a nanotube in advance. It is only possible to separate metallic
from semiconducting tubes by using an electrical ¯eld [22]. Metallic nanotubes with their
diameter of a few nm represent the ultimate conducting wire whereas the semiconducting
ones can be used as transistors [23{25] even on a transparent and °exible substrate [26]. The
transistors can be optimized by the chemical control of the nanotube-electrode interface [27].
Quantum dots [28, 29] and spin valves [30{32] can be built alike simple logic gates [33] and a
Y-junction recti¯er [34].
Carbon nanotubes have a very interesting property: they are "1-dimensional" molecules [35].
This has to be explained in a few words. In general, quantum con¯nement leads to a spacing
of the allowed eigenenergies. Electrons cannot hop into a higher energy level if the thermal
energy is much smaller than this energy di®erence. In a nanotube an electron is con¯ned in the
directions perpendicular to the tube axis. The nanotube becomes a 1-dimensional conductor.
For several years members of our research group are exploring the electrical properties of
this very special conductor. The behavior of carbon nanotubes is investigated with electrical
transport measurements at low temperatures (down to 50 mK) and in high magnetic ¯elds
(up to 10 T).
The raw material for the ¯rst experiments [36{38] were multi-wall carbon nanotubes ob-
tained from L. Forr¶o (Ecole Polytechnique F¶ed¶erale de Lausanne) which were produced using
laser ablation. The multi-wall carbon nanotubes were used to investigate the suppression of
tunnelling [36, 39], multiple Andreev re°ection [28, 37], electrical spin injection [30{32] and
quantum dots [37, 40{43].
The next step was to grow single-wall carbon nanotubes using chemical vapor deposition
(CVD) [8,44{46]. This procedure has the advantage to be faster than an external collaboration
and in addition the growth of the tubes directly on the device makes the samples ready for
use without an additional treatment.
It was veri¯ed that the CVD grown tubes are suitable of for electrical devices [47]. Vibrating
nanotubes [48] and an ambipolar ¯eld-e®ect transistor [23] were studied. Kondo e®ect [49]
and Fano-Resonances [50] were investigated as well.
The latter experiments reveal one common de¯ciency. The grown tubes are often not sepa-
rated but bundled [47] (Figure 6.10). Moreover it is not clear if they are multi- or single-wall
tubes. This means for electronic transport measurements that several tubes are measured si-
multaneously. Thus the tube with the best conductivity dominates the measurement, whereas
the other tubes perturb the measured signal by there presence.
The main focus of this thesis is the development of a growth process of single-wall carbon
nanotubes by using CVD. The aim is to overcome the problem of bundling. The grown
nanotubes have to be free of lattice defects and they need to have good electrode-nanotube
contacts in order to make them suitable for electronic transport measurements. They have
to lay °at, well separated and optimally distributed on SiO2 our standard substrate. On the
one hand the tube density should not be too high since this would increase the probability
of shortcuts between the electrodes due to nanotube-nanotube contacts. On the other hand
it should not be too low since this would make the localization of an appropriate nanotube
much more time consuming (Figure 1.2).
Two ways to achieve this goal were tried. The single-wall nanotubes can be bought, dissolved
in a solvent and spread after cleaning and separation [51{57], as in the thesis [46]. The second
possibility is to grow the tubes directly on the device as presented in this thesis.
Growing carbon nanotubes with CVD is very simple, at least in principle. There are only
a few essential things needed: an oven, a substrate, a catalyst and a carbon feedstock. The
main challenge is to acquire the right knowhow.
The ¯rst step was to build up the CVD system. Afterwards the proper growth conditions
and a simple method to check the demanded properties of the grown tubes had to be found.
Scanning electron microscopy (SEM) is the standard characterization tool used in this thesis.
Transmission electron microscopy (TEM) is a helpful mean in order to show that the tubes
are separated and single-wall, since it allows the investigation of the tubes' internal structure.
Atomic force microscopy (AFM) and Raman spectroscopy are used in addition.
Outline of this thesis
² Chapter 2 gives a short overview with respect to the properties, the growth and the
characterization of carbon nanotubes.
² The oven and the gas system are delineated in Chapter 3. Di®erent carbon feedstocks
were used: ethylene/hydrogen, methane, methane/ethylene and methane/hydrogen.
² The steps towards a suitable catalyst are presented in Chapter 4. Evaporated and
liquid based catalysts were tested. An iron molybdenum alumina catalyst dissolved in
2-propanol provides the best results.
² Chapter 5 gives a comparison of the results obtained utilizing di®erent growth processes,
and describes the formation of amorphous carbon and the oxidation of nanotubes.
² Chapter 6 summarizes experiments on di®erent TEM grids (Au, Cu, Mo, Ni, stainless
steel, Ti, quantifoils) and silicon nitride windows.
² The results from collaborations with other group members are presented in Chapter 7.
These experiments show the good quality of the grown tubes
Bernadine Dunfee
No full textBERNADINE L. DUNFEE
NBS: 1943-1976
Birth: May 13, 1914, Coal Grove, Ohio
Death: October 14, 2009
Education:
Wilmington College (Ohio), BS (education), 1939
George Washington University, MS (physics), 1955
Principal Field:
Voltage and Current Ratio Standards
Positions Held at NBS:
Project Leader, Electricity Division
Chief, Electrical Instruments Section, Electricity Division
NBS Museum Committee (w/ Francis Silsbee)
Honors:
U. S. Department of Commerce Silver Medal, 1969
NBS Nominee for Federal Women’s Award, 1968
Institute of Electrical and Electronics Engineers (IEEE): IEEE Prize Paper, 1960
Sigma Pi Sigma
Sigma Xi
Memberships:
Institute of Electrical and Electronics Engineers, Senior Member, Fellow
American National Standards Institute (ANSI)
Standards Alumni Association, Director, 1988-1994
Publications:
Numerous papers related to electrical standards and measurements, including:
Methods for Measuring the “Q” of Large Reactors (coauthor),Trans. AIEE Winter Meeting, (Jan-Feb 1956)
An A-C Kelvin Bridge for the Audio-Frequency Range, AIEE Trans., (May 1956)
A Standard Current Transformer and Comparison Method... , IRE Trans. Instr., (1960)
Method for Calibrating a Standard Volt Box, NBS J. Res. 67, (Jan-Mar 1963)
The Design and Performance of Multi-Range Current Transformer Standards for Audio Frequencies, IEEE Trans. IM-14, 4, (Dec. 1965)
An International Comparison of Current Ratios at Audio Frequencies (co-author), IEEE Trans. IM-14, 4, (Dec. 1965)
Electrical Standards and Measurements (co-author), ElectroTechnology, 79, (Jan. 1967)
Resistive Voltage Ratio Standard and Measuring Circuit (co-author), IEEE Trans. IM-19, (Nov. 1970
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