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Andrew D. Koffman

Publications

Milligram mass metrology using an electrostatic force balance

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

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

Author(s)
Frederic Overney, Nathan E. Flowers-Jacobs, Blaise Jeanneret, Alain Rufenacht, Anna E. Fox, Jason M. 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-Based Full Digital Bridge for High-Accuracy Impedance Comparisons

Author(s)
Frederic Overney, Nathan E. Flowers-Jacobs, Blaise Jeanneret, Alain Rufenacht, Anna E. Fox, Jason M. 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

Alignment and testing of the NIST Calculable Capacitor

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

Eddy Current Rail Inspection Using AC Bridge Techniques

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
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Created October 9, 2019