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Search Publications by: Andrew D. Koffman (Fed)

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Displaying 1 - 25 of 33

Comparison of a 1 nF Capacitor with a 1 kO Resistor Using a Digital Impedance Bridge

March 27, 2024
Author(s)
Yicheng Wang, Stephan Schlamminger, Dean G. Jarrett, Alireza Panna, Andrew D. Koffman
This paper reports our effort to improve a digital impedance bridge. The limit of the bridge resolution and stability is less than 3 parts in 10^9 for the nominal 1:1 impedance comparison of two 100 pF capacitors. The type-A uncertainty for comparison of a

New Method for Determining Time Constant of Resistors

March 21, 2023
Author(s)
Yicheng Wang, Dean G. Jarrett, Andrew D. Koffman, Stephan Schlamminger
We report a new method for determining the time constant of ac resistors with values around 10 kΩ, using a digital impedance bridge for comparison of two nominally equal resistors. The method involves adding a probing capacitor in parallel to one of the

Milligram mass metrology using an electrostatic force balance

September 28, 2016
Author(s)
Gordon A. Shaw, Julian Stirling, John A. Kramar, Alexander D. Moses, Patrick J. Abbott, Richard L. Steiner, Andrew D. Koffman, Jon R. Pratt, Zeina J. Kubarych
Although mass is typically defined within the International System of Units (SI) at the Kilogram level, the pending redefinition of the SI provides an opportunity to realize mass at any scale using electrical metrology. We propose the use of an

Josephson-Based Full Digital Bridge for High-Accuracy Impedance Comparisons

July 9, 2016
Author(s)
Frederic Overney, Nathan Flowers-Jacobs, Blaise Jeanneret, Alain Rufenacht, Anna Fox, Jason Underwood, Andrew D. Koffman, Samuel P. Benz
This paper describes a Josephson-based impedance bridge capable of comparing any types of impedance over a large bandwidth. The heart of the bridge is a dual AC Josephson Voltage Standards (ACJVS) source which offers unprecedented flexibility in high

Josephson-Based Full Digital Bridge for High-Accuracy Impedance Comparisons

June 24, 2016
Author(s)
Frederic Overney, Nathan Flowers-Jacobs, Blaise Jeanneret, Alain Rufenacht, Anna Fox, Jason Underwood, Andrew D. Koffman, Samuel P. Benz
This paper describes a Josephson-based full digital impedance bridge capable of comparing any two impedances, regardless of type (R-C, R-L, or L-C), over a large frequency range. At the heart of the bridge are two Josephson arbitrary waveform synthesizer

Alignment and testing of the NIST Calculable Capacitor

August 24, 2014
Author(s)
Yicheng Wang, Felipe Guzman, Corey A. Stambaugh, Radek Smid, Hugo Zuniga Calvo, Andrew D. Koffman, Jon R. Pratt, John R. Lawall
This paper reports progress on the NIST effort to develop a new calculable capacitor, focusing on improvement of the guard electrode motion control as well as issues associated with the overall electrode alignment. Design of a multi-wavelength Fabry-Perot

Eddy Current Rail Inspection Using AC Bridge Techniques

February 26, 2013
Author(s)
Andrew D. Koffman, Bryan C. Waltrip, Yicheng Wang
AC bridge techniques commonly used for precision impedance measurements have been adopted to develop an eddy current sensor for rail defect detection. By using two detection coils instead of just one in a conventional sensor, we can balance out the large

Evaluation of a Capacitance Scaling System

December 1, 2007
Author(s)
Svetlana Avramov-Zamurovic, Andrew D. Koffman, Bryan C. Waltrip, Yicheng Wang
A capacitance scaling system from 10 nF to 100 mF [1], [2] has been implemented at the National Institute of Standards and Technology (NIST). Standard four-terminal-pair (4TP) capacitors are characterized using a capacitance scaling calibration procedure

Dissipation Factors of Fused-Silica Capacitors in the Audio Frequency Range

April 1, 2007
Author(s)
Yicheng Wang, Andrew D. Koffman, Gerald FitzPatrick
We describe dissipation factor measurements of 10 pF fused-silica capacitance standards from 50 Hz to 20 kHz, using a toroidal cross capacitor and a 10 pF nitrogen-filled capacitor as the references. The relative combined standard uncertainties are 0.56x10

Improved 1 kHz Capacitance Calibration Uncertainty

May 30, 2002
Author(s)
Anne-Marie Jeffery, Andrew D. Koffman
Uncertainties for 1 kHz capacitance calibrations have been decreased at the National Institute of Standards and Technology (NIST). The improvements are based on frequency-dependence characterization from 1592 Hz to 1 kHz. The relevant measurements and the

A Capacitance Measurement System Using an Inductive Voltage Divider (IVD) Bridge

July 1, 2001
Author(s)
Bryan C. Waltrip, Andrew D. Koffman, S. Avramov
A new system to characterize the magnitude and phase characteristics of 1 pF to 1 uF capacitance standards over the 50 Hz to 100 kHz frequency range is described. The system has been developed to provide measurement support for LCR meters and general

High-Dimensional Empirical Linear Prediction (HELP) Toolbox, version 2.2

February 28, 2001
Author(s)
Andrew D. Koffman, T. M. Souders, Gerard N. Stenbakken, Hans Engler
The High-Dimensional Empirical Linear Prediction (HELP) Toolbox is an optimization tool designed specifically to meet the requirements of test and measurement engineers. For many electronic devices and instruments, it is not physically or economically

Low-Frequency Impedance Calibrations at NIST

July 1, 2000
Author(s)
Andrew D. Koffman, Yui-May Chang
This paper presents an overview of the low-frequency impedance measurement services offered through the Impedance Calibration Laboratory (ICL) at the National Institute of Standards and Technology (NIST). Emphasis will be given to recent improvements as

The Sensitivity of a Method to Predict a Capacitor's Frequency Characteristic

April 1, 2000
Author(s)
S. Avramov, Andrew D. Koffman, Nile M. Oldham, Bryan C. Waltrip
A joint effort between the U.S. Naval Academy and the National Institute of Standard and Technology (NIST) resulted in the development of a method to characterize the capacitance and dissipation factor of a set of commercial standard four terminal-pair

Software to Optimize the Testing of Mixed-Signal Devices

June 1, 1999
Author(s)
Gerard N. Stenbakken, Andrew D. Koffman, T. M. Souders
New software is now available to help test and measurement engineers optimize the testing of complex electronic devices. Examples of products that are benefiting from this software range from A/D and D/A converters to multi-range precision instruments. The

High-Dimensional Empirical Linear Prediction (HELP) Toolbox User's Guide, Version 2.2

May 1, 1999
Author(s)
Andrew D. Koffman, T. M. Souders, Gerard N. Stenbakken, Hans Engler
This user's guide will assist software users in the understanding of the theory and procedures underlying the High-dimensional Empirical Linear Prediction (HELP) Toolbox, developed for use with the MATLAB(r) mathematical software environment. The HELP