High Resolution Time Interval Counter

Victor S. Zhang, Dick D. Davis, Michael A. Lombardi

Abstract: In recent years, we have developed two types of high resolution, multi-channel time interval counters. In the NIST two-way time transfer MODEM application, the counter is designed for operating primarily in the interrupt-driven mode, with 3 start channels and 3 stop channels. The intended start and stop signals are I PPS, although other frequencies can also be applied to start and stop the count. 'The time interval counters used in the NIST Frequency Measurement and Analysis System are implemented with 7 start channels and 7 stop channels. Four of the 7 start channels are devoted to the frequencies of 1 MHz, 5 MHz or 10 MHz, while triggering signals to all other start and stop channels can range from I PPS to 100 kHz. Time interval interpolation plays a key role in achieving the high resolution time interval measurements for both counters. With a 10 MHz time base, both counters demonstrate a single-shot resolution of better than 40 ps, and a stability of better than 5 x 10^-12 (ox(r) after self test of 1000 seconds). The maximum rate of time interval measurements (with no dead time) is 1.0 kHz for the counter used in the MODEM application and is 2.0 kHz for the counter used in the Frequency Measurement and Analysis System. The counters are implemented as plug-in units for an AT-compatible personal computer. This configuration provides an efficient way of using a computer not only to control and operate the counters, but also to store and process measured data.
Published in: Proceedings of the 26th Annual Precise Time and Time Interval Systems and Applications Meeting
December 6 - 8, 1994
Hyatt Regency Reston Town Center
Reston, Virginia
Pages: 191 - 200
Cite this article: Zhang, Victor S., Davis, Dick D., Lombardi, Michael A., "High Resolution Time Interval Counter," Proceedings of the 26th Annual Precise Time and Time Interval Systems and Applications Meeting, Reston, Virginia, December 1994, pp. 191-200.
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