Skip to main content

NOTICE: Due to a lapse in annual appropriations, most of this website is not being updated. Learn more.

Form submissions will still be accepted but will not receive responses at this time. Sections of this site for programs using non-appropriated funds (such as NVLAP) or those that are excepted from the shutdown (such as CHIPS and NVD) will continue to be updated.

U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Measuring Time and Comparing Clocks

Published

Author(s)

Judah Levine

Abstract

I will discuss methods of comparing and synchronizing clocks and the procedure of characterizing their performance in terms of the two-sample Allan variance. I will describe methods that are used when the device under test and the reference device are in the same facility and when they are at different locations linked by a communications channel. The reference device can be a national time scale, and I will briefly describe how national time scales are defined. In each case I will use the Allan variance as a tool to understand the characteristics and limitations of the various methods. I will also introduce the concepts of traceability and of a cost-benefit analysis into the synchronization procedure.
Citation
Handbook of Measurement in Science and Engineering
Volume
Ch. 59
Publisher Info
John Wiley, Hoboken, NJ

Keywords

Allan Variance, Common-View, GPS Satellites, Network Time Protocol, Time and Frequency Distribution

Citation

Levine, J. (2016), Measuring Time and Comparing Clocks, John Wiley, Hoboken, NJ, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915305 (Accessed October 14, 2025)

Issues

If you have any questions about this publication or are having problems accessing it, please contact [email protected].

Created April 1, 2016, Updated February 19, 2017
Was this page helpful?