100/180 MM GRAPHICS RECORDER: USER GUIDE
HA261742
Issue 16 Nov 04
User Guide
Page 100
4.5.1 NETWORK ADDRESS (Cont.)
DEFAULT GATEWAY
To deliver traffic from one subnet to another, devices called ‘routers’ or ‘gateways’ are placed between segments. The
default gateway address informs each network device where to send data if the target station does not reside on the
same subnet as the source.
SNTP ENABLE
This tick box allows time synchronisation from a Simple Network Time Protocol (SNTP) server to be enabled and
disabled. When enabled, the instrument time is updated every 15 minutes.
SNTP SERVER
If 'Obtain from BootP server' is selected as the IP address look-up (see above), then this address appears automati-
cally. Otherwise this area allows an IP address to be entered for the SNTP server.
Notes:
1
SNTP is a protocol that allows clients on a TCP/IP network to set their times to that of a server - port
number 123. The recorder can act both as a client and as a server; when acting as a server, the resolution
is 1 msec.
2.
SNTP time is based on elapsed seconds since 00:00 hrs on 1st January 1900. The time is not affected by
time zones or daylight saving adjustments.
3.
If the instrument time differs from the SNTP time by less than 2 seconds, the instrument time is updated
gradually (1 msec 8 times a second) to prevent time change events being recorded. If the difference is
greater than 2 seconds, this is defined as a 'time change event', the results of which are that the recorder
time is immediately updated, and a green line is drawn across the chart (vertical trend/history only) to
indicate the time change.
4.
If more than 5 time change events occur within 24 hours, a 'Time Synchronisation failure' instrument
alarm is set 24 hours after the first event. Once synchronisation is re-established, the alarm self-clears
within 24 hours.
5.
An 'SNTP server failure' instrument alarm is flagged if the configured server cannot be accessed, or if the
year received from the server is less than 2001 or more than 2035.
6.
When the instrument is acting as a server and a "Clock Failure' instrument alarm is active, the server time
is set to 1/1/1900 which is ignored by clients.
7.
Servers such as Microsoft 'TimeServ' cannot be used with this series of instruments because they are not
SNTP servers.
