Alstom iSTAT M355, Manual, Page: 31 / 154

User Manual M3x5/EN M/B
iSTAT M3x5
Page 29
8.9 Real Time Synchronization module C
A Synchronized real-time clock (RTC) is an essential part of any Class A analyser for proper
chronological determination of events. To differentiate cause from consequence, to follow a
certain event from its origin to manifestation in other parameters it is very important that each
and every event and recorded measurement on one instrument can be compared with
events and measurements on other devices. Even if instruments are dispersed, which is
normally the case in electro distribution networks, events have to be time-comparable with
accuracy better than a single period.
The Synchronisation module is used to synchronise the RTC of the device to a standard
which is also used by other related devices. This maintains its accuracy for correct
aggregation intervals and time stamps of recorded events appearing in the monitored electro
distribution network.
Different types of RTC synchronisation are available:
- IRIG-B modulated; 1 kHz modulation with <1ms resolution.
- IRIG-B un-modulated (level shift)
-
1PPS + RS232 Date & Time telegram (from GPS)
PLEASE NOTE
SNTP synchronisation is also possible via Ethernet communication if the Ethernet
communication module is fitted.
8.9.1
GPS time synchronization
1PPS and serial RS232 communication with NMEA 0183 sentence support. GPS interface is
designed as 5 pole pluggable terminal (+5V for receiver supply, 1PPS input and standard
RS232 communication interface). Suggested GPS receiver is GARMIN GPS18x.
8.9.2 IRIG time code B (IRIG-B)
Un-modulated (DC 5V level shift) and modulated (1 kHz) serial coded format with support for
1PPS, day of year, current year and straight seconds of day as described in standard IRIG-
200-04. Supported serial time code formats are IRIG-B007 and IRIG-B127.
Interface for modulated IRIG-B is designed as BNC-F terminal with 600 Ω input impedance,
and the interface for un-modulated IRIG-B is pluggable terminals.
8.9.3 Simple Network time protocol (SNTP)
Synchronization via Ethernet requires access to an NTP server.
PLEASE NOTE
SNTP can usually maintain time to within tens of milliseconds over the public Internet, but
the accuracy depends on infrastructure properties - asymmetry in outgoing and incoming
communication delay affects systematic bias. It is recommended that a dedicated network
rather than public network is used for synchronisation purposes.
CAUTION
RTC synchronisation is an essential part of a Class A instrument. If adequate RTC
synchronisation is not provided the
M3x5 will only operate as a Class S instrument.