GPS disciplined oscillators (GPSDOs) are commonly used as references for frequency calibrations. Over long intervals, a GPSDO is an inherently accurate source of frequency because it is continuously adjusted to agree with the Coordinated Universal Time (UTC) time scale maintained by the United States Naval Observatory (USNO). However, many frequency calibrations last for intervals of one day or less, and it can be difficult for metrologists to determine the uncertainty of a GPSDO during a short interval, and even more difficult to prove their uncertainty claims to skeptical laboratory assessors. This paper can serve as a guide to metrologists and laboratory assessors who work with GPSDOs as frequency standards. It describes the relationship between GPS time and Coordinated Universal Time (UTC) and explains how GPS time is traceable to the SI. It discusses how a GPSDO utilizes the GPS signals to control the frequency of its local oscillator. It explains how to estimate frequency stability, and how to apply frequency stability estimates to determine the uncertainty of a GPSDO used as the reference for a frequency calibration.
Proceedings Title: Proceedings of the 2013 NCSL International Workshop and Symposium
Conference Dates: July 14-18, 2013
Conference Location: Nashville, TN
Conference Title: Conference of the 2013 NCSL International Workshop and Symposium
Pub Type: Conferences
calibration, disciplined oscillator, frequency, GPS, traceability