20
GPS Network Time Server
SALES: 0118 965 5100
Performance Characteristics
Environment
The GPS Network Time Server meets the safety recommendations for industrial equipment
•
Operating temperature:
- 40 °C to + 85 °C ;
•
Relative humidity:
90%, no condensation, at + 40 °C ;
•
Low voltage safety:
per EN 60950 ;
•
Electromagnetic compatibility:
per EN 50082-1, 1992 issue
•
Radiated perturbations transmitted: per EN 55022 C1ass B, 1994 issue.
Internal time generation
The initial accuracy of the system internal time is conditioned by the adjustment source used
by the user. The 1-pps signal rising edge gives the precise time for the second roll over. The
accuracy of the 1-pps signals relative to the UTC (GPS) is:
•
Accuracy in synchronization with GPS:
<
±
100 ns (at 1
σ
, without SA on GPS);
•
Accuracy with GPS unavailable (1):
<
±
20
µ
s (at 1
σ
, without SA on GPS).
(1) 24 hrs after GPS synchronization of duration > 48 hrs, at almost constant temperature;
The system accuracy, following disconnection of the U.T.C. time reference source depends
directly on the oscillator used, i.e. the OCXO described in paragraph "4.2. ". However,
following locking for a sufficient period on GPS broadcasting, the intrinsic stability of the
oscillator is improved by the system internal algorithm. Thus, if locking on GPS lasted at
least 48 hrs and that subsequent unlocking follows for 24 hrs, the internal reference accuracy
is better than: +20
µ
s
Frequency outputs
The four frequency outputs each deliver a 10 MHz frequency sine wave signal. These outputs
are delivered by the OCXO frequency pilot included in the timekeeper.
The performance characteristics of these outputs are:
•
Frequency accuracy(1), with GPS available:
<
±
2 x 10-12 ;
•
Frequency accuracy(1), with GPS unavailable(2): <
±
3 x 10-10.
(1) Average frequency accuracy over 24 hrs at 1
σ
,
(2) 24 hrs after last synchronization on GPS lasting > 48 hrs, at almost constant temperature.
NTP reference accuracy
The reference delivered by the GPS Network Time Server has an accuracy level equal to the
internal time generation accuracy. The processing of client request messages to the server
introduces an average internal error less than 1 ms.
