Trimble Outdoors Part Number 45005-00-ENG manual Timing Pulse Output PPS

System Operation 5

Timing Pulse Output (PPS)

A pulse-per-second (PPS), 1 microsecond-wide pulse is available on the Acutime 2000’s interface connector. The pulse is sent once per second and the leading edge of the pulse is synchronized to UTC or GPS time. The pulse shape is affected by the distributed capacitance of the attached cabling and input circuit. The leading edge is typically less than 20 nanoseconds wide. The pulse's trailing edge should never be used for timing applications. An accurate timing pulse is available only when the Acutime 2000 is operating in the static Overdetermined Clock mode.

!Note – GPS time differs from UTC (Universal Coordinated Time) by a small, sub-microsecond offset and an integer-second offset. The small offset is the steering offset between the GPS DoD clock ensemble and the UTC (NIST) clock ensemble. The large offset is the cumulative number of leap seconds since 1 January 1970, which, on 31 December 1998, was increased from 12 to 13 seconds. Historically, the offset increases by one second approximately every 18 months, usually just before midnight on 30 June or 31 December. System designers should note whether the output time is UTC or GPS time.

!Note – The event time reported in 8F-0B and 8-AD is corrected for the fractional UTC offset if UTC PPS (default) is selected.

5-14 Acutime 2000 Synchronization Kit User Guide