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Search Publications by: Leon Chao (Fed)

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Displaying 1 - 25 of 42

Redetermination of the Gravitational Constant using the BIPM Torsion Balance

July 8, 2024
Author(s)
Stephan Schlamminger, Leon Chao, David B. Newell, Vincent Lee, Clive Speake
For the past several years, we have been using the torsion balance developed at the Bureau International des Poids et Mesures (BIPM) to measure the gravitational constant $G$. The most notable feature of the apparatus is that it allows the measurement of

Application of Electrical Standards to Torque Realization: A Device to Measure up to 1Nm

February 14, 2024
Author(s)
Zane Comden, Stephan Schlamminger, Frank Seifert, David B. Newell, Leon Chao
This paper describes the next generation prototype of the Electronic NIST Torque Realizer (ENTR) project. The first prototype version (ENTR-v1) has been able to realize low-range torques (on the order of 1×10-3 Nm) to uncertainties of less than 1000 parts

The design and performance of an electronic torque standard directly traceable to the revised SI

May 25, 2023
Author(s)
Zane Comden, John-Edward Draganov, Stephan Schlamminger, Frank Seifert, Charles Waduwarage Perera, David B. Newell, Leon Chao
The United States National Institute of Standards and Technology (NIST) has been developing a new device for primary standard realization of torque utilizing established trace- ability to the quantum-electrical International System of Units (SI) standards

Using the Kibble Principle for One-Step Traceability for Mass, Force, and Torque

May 8, 2023
Author(s)
Stephan Schlamminger, Leon Chao, Zane Comden, John-Edward Draganov, Thapelo Given Mametja
Many technologies contributed to the 2019 revision of the international system of units. Notable is a mechanical apparatus, the Kibble balance. It allows the precise comparison of electrical power to mechanical power with relative uncertainties close to 1

Determination of the Gravitational Constant Using a BIPM Balance

December 12, 2022
Author(s)
Stephan Schlamminger, Leon Chao, Vincent Lee, David B. Newell, Clive Speake
With the torsion balance developed at the Bureau International des Poids et Mesures (BIPM), the Newtonian constant of gravitation, $G$, can be measured with two methods. In the Cavendish method, the external gravitational torque is obtained from the

A Macroscopic Mass From Quantum Behavior In An Integrated Approach

December 10, 2022
Author(s)
Frank Seifert, Alireza Panna, Lorenz Keck, Leon Chao, Shamith Payagala, Dean G. Jarrett, Dipanjan Saha, Randolph Elmquist, Stephan Schlamminger, Albert Rigosi, David B. Newell, Darine El Haddad
The revision of the International System of Units (SI) on May 20th, 2019, has enabled new improved experiments to consolidate and simplify electrical and mechanical metrology currently underway. Historically within the SI, the definition of energy was only

DIMENSIONAL METROLOGY IN DETERMINATION OF G WITH BIPM'S TORSION BALANCE

November 7, 2022
Author(s)
Vincent Lee, Stephan Schlamminger, Leon Chao, David B. Newell, Jon Pratt, Craig Shakarji, Clive Speake
This paper discusses the dimensional metrology challenges encountered while performing G measurements using the BIPM torsion balance and our solutions.

Calculation of magnetic forces and torques on the Kibble coil

October 22, 2022
Author(s)
Stephan Schlamminger, Lorenz Keck, Frank Seifert, Leon Chao, Darine El Haddad, Shisong Li
Analytically the force and torques on a coil in a field of magnetic flux density can be calculated one of two ways. The line integral can be conducted along the coil's wire, summing up the differential force contribution. For each differential line segment

Precision Engineering For Gravitational Experiments

October 10, 2022
Author(s)
Stephan Schlamminger, Leon Chao, Vincent Lee, David B. Newell, Jon Pratt, Clive Speake
Four fundamental forces, or technically more correct interactions, are known in physics. The gravitational force is one of them and is a mysterious one. Gravity has an infinite range, just like the electromagnetic interaction. However, in contrast to

Design of an electrostatic feedback for an experiment to measure G

June 20, 2022
Author(s)
Stephan Schlamminger, Leon Chao, Vincent Lee, David B. Newell, Clive Speake
The torsion pendulum at the heart of the BIPM apparatus to measure the gravitational constant, $G$, is used to measure the gravitational torque between source and test-mass assemblies with two methods. In the Cavendish method, the pendulum moves freely. In

A New Spin on Kibble: A Self Calibrating Torque Realization Device at NIST

June 3, 2022
Author(s)
Zane Comden, Stephan Schlamminger, Charles Waduwarage Perera, Frank Seifert, David B. Newell, Jay H. Hendricks, Barbara L. Goldstein, Leon Chao
After the 2019 redefinition of the International System of Units (SI), torque no longer needs to be traceable to a calibrated weight suspended from a known lever arm. Specifically, a modification of the Kibble principle used for realizing the kilogram

The Crane Operator's Tricks and other Shenanigans with a Pendulum

February 18, 2022
Author(s)
Stephan Schlamminger, Leon Chao, David B. Newell, Vincent Lee
The dynamics of a swinging payload suspended from a stationary crane can be described as a simple pendulum, typically an unwelcome phenomenon on a construction site. An experienced crane operator can deliver a swinging payload and stop dead on target in a

The Design of an Instrument to Realize Small Torque at NIST

August 22, 2020
Author(s)
Leon S. Chao, Rafael Marangoni, Frank C. Seifert, Darine El Haddad, Jon R. Pratt, David B. Newell, Stephan Schlamminger
After the recent redefinition of the International System of Units (SI), torque no longer needs to be traceable to a calibrated mass in a gravitational field suspended from a known lever arm and disseminated through a chain of torque transducers.An SI

The Design and Development of a Tabletop Kibble Balance at NIST

May 23, 2019
Author(s)
Leon S. Chao, Frank C. Seifert, Darine El Haddad, Julian Stirling, David B. Newell, Stephan Schlamminger
On November 16, 2018, the 26th General Conference on Weights and Measures (CGPM) voted unanimously to revise the International System of Units (SI) from a system built on seven base units to one built on seven defining constants and will officially become

The Design and Development of a Tabletop Kibble Balance at NIST

March 20, 2019
Author(s)
Leon S. Chao, Frank C. Seifert, Darine El Haddad, Stephan Schlamminger
A global paradigm shift to redefine the International System of Units (SI) from a system based on seven fundamental units to seven fundamental constants is well under way. More specifically, the unit of mass, the kilogram, will be realized via a fixed

Measurement of the Planck constant at the National Institute of Standards and Technology from 2015 to 2017

July 28, 2017
Author(s)
Darine El Haddad, Frank Seifert, Leon Chao, Antonio Possolo, David B. Newell, Jon R. Pratt, Carl J. Williams, Stephan Schlamminger
Researchers at the National Institute of Standards and Technology(NIST) estimate the value of the Planck constant as h = 6.62606994(10) x 10^-34 Js, hence with relative standard uncertainty 15.3 x 10^-9. This measurement result is based on over 17,000

Bridging classical and quantum mechanics

September 28, 2016
Author(s)
Darine El Haddad, Frank C. Seifert, Leon S. Chao, Shisong Lee, David B. Newell, Jon R. Pratt, Carl J. Williams, Stephan Schlamminger
Using a watt balance and a frequency comb, a mass-energy equivalence is derived. The watt balance compares mechanical power measured in terms of the meter, the second, and the kilogram to electrical power measured in terms of the volt and the ohm. A direct

Design of a Table-Top Watt Balance

July 26, 2016
Author(s)
Stephan Schlamminger, Jon R. Pratt, David B. Newell, Frank C. Seifert, Michael Liu, Leon S. Chao, Luis Manuel Pea Prez, Shisong Li, Darine El Haddad
Measurements of the Planck constant with watt balances using 1 kg masses have achieved relative standard uncertainties below 2 x 10-8. Having established a metrological link between the kilogram and this fundamental constant of nature, a redefinition of

First mass measurements with the NIST-4 watt balance

July 10, 2016
Author(s)
Darine El Haddad, Leon S. Chao, Frank C. Seifert, David B. Newell, Jon R. Pratt, Stephan Schlamminger
In the past four years, we have constructed a new watt balance at the National Institute of Standards and Technology (NIST), with the goal to realize the unit of mass after the redefinition of the International System of Units, expected to occur in 2018

A precise instrument to determine the Planck constant, and the future kilogram

June 21, 2016
Author(s)
Darine El Haddad, Frank C. Seifert, Leon S. Chao, David B. Newell, Jon R. Pratt, Carl J. Williams, Stephan Schlamminger, Shisong Li
A precise instrument, called a watt balance, compares mechanical power measured in terms of the meter, the second and the kilogram to electrical power measured in terms of the volt and the ohm. A direct link between mechanical action and the Planck

Coil motion effects in watt balances: a theoretical check

February 10, 2016
Author(s)
Stephan Schlamminger, Shisong Li, Darine El Haddad, Frank C. Seifert, Leon S. Chao, Jon R. Pratt
A watt balance is a precision apparatus for the measurement of the Planck constant that has been proposed as a primary method for realizing the unit of mass in a revised International System of Units. In contrast to an ampere balance, which was