WESTERSTRAND Analogue NTP Clock, Руководство пользователя

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WESTERSTRAND
Document: DOK11018en02
Author: PM/CF
Analogue NTP Clock
Date: 2020-09-24
Page: 10 of 21
WESTERSTRAND URFABRIK AB
P.O. Box 133 Tel. +46 506 48000 Internet:: http://www.westerstrand.se
SE-545 23 TÖREBODA Fax. +46 506 48051 E-mail: info@westerstrand.se
NTP
NTP settings
General description
Westerstrand NTP Clients has several features to achieve a reliable and accurate time. The configuration of the
different facilities is flexible and the features can be selected or deselected depending on each customer’s
individual needs.
As a NTP Client the unit has three different ways to determine the most accurate and reliable candidates to
synchronize the system clock. Which model that is used depends on the specific installation and the customer
requirements. The NTP client has also a server list where up to 5 different time servers can be entered.
The three different ways are:
1. FIRST Always use the first server in the list if available. If not available take next one.
This suits installations where it is more important to know exactly from where the clients get time than to have the
most accurate time. The other NTP servers in the list will then be more of backup servers.
2. STRATUM Use the NTP server with best stratum. The software sends a request to all servers in the list and uses
the time from the one with best stratum. If same stratum it will use the one that is first in the server list.
This suits installations where it is important that the time is coming from a time server high up in the pyramid.
3. MEDIAN Send a request to all servers in the list and use the median value (the NTP server that is in the middle).
This will filter out all misleading time messages.
In addition to these rules there are some more features such as synchronization limits and a special clock adjusting
algorithm where the speed of internal oscillator is increased or decreased depending on the difference between the
internal clock and the NTP message. All of this to avoid false and inaccurate time and to give a, when needed,
smooth time adjustment without time jumps.
A clock discipline algorithm is also included. This algorithm measures the oscillators drift over a longer period and
makes compensations for the drift.