It defines the "second" as the standard unit of time interval—one of the seven base units of the International System of Units (SI).
, titled " Stopwatch and Timer Calibrations ," is the primary recommended practice guide for metrologists and calibration technicians in the United States. Originally published in 2004 and updated in January 2009 , it serves as a comprehensive manual for verifying the accuracy of time-interval measuring devices. nist sp 960-12
The publication explains that to realize this definition, scientists must build an apparatus to observe these oscillations. NIST-F1 is that apparatus. It defines the "second" as the standard unit
As with many NIST special publications, the document is freely redistributable and not subject to copyright restrictions within the United States. The publication explains that to realize this definition,
Given that NIST SP 960-12 is a public document, it can be accessed through official government channels:
Measuring the frequency of the device’s internal oscillator to calculate its accuracy.
The guide is structured to provide both theoretical and practical instruction, covering everything from the fundamental units of time to specific field-testing methods.