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| Westermo introduces T208 Ethernet switch with time synchronization |
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June 13, 2007 - The T208 Ethernet switch is the only one able to operate with high accuracy time synchronization on both the SNTP/NTP (Simple Network Time Protocol / Network Time Protocol) or PTP (Precision Time Protocol) open standard protocols. It also allows for considerable savings in the cost of industrial automation networks for applications such as high speed data acquisition, high speed mechanical assemblies and high voltage or medium voltage substation automation.
In industrial automation, Ethernet networks have always been limited by the latency jitter of data packet transmission inside the switches. Depending on the network load, data packet size and the number of switches between the server and the client, data transmission inside an Ethernet switch introduces time latency jitter of up to several milliseconds. A packet that enters the switch first can even go out after one that arrives later due to switch QoS techniques. Furthermore, a network with several off-the-shelf switches will accumulate time synchronization errors for each switch on the network path between the time server and time client. Precise data analysis needed for process automation then becomes impossible (multi-axle synchronization in assembly machines, for instance).
Westermo’s T208 switch allows events to be time stamped with high accuracy precision providing a full and exact history of data events. Sophisticated or critical industrial processes, be they in real time or not, can now be managed with the off-the-shelf SNTP Ethernet protocol.
1 micro second accuracy, decreasing to 20 nano seconds when using PTP protocol
To ensure better accuracy, Westermo has implemented the new PTP protocol based on IEEE1588. By enabling the T200s as PTP Grand master and/or PTP Transparency, the accuracy is further improved. It is possible to achieve performances of 20 to 40 nanoseconds by using the PTP protocol.
Distant sites worldwide: different places, same time
GPS or free running clocks of the servers can be used as a time reference. GPS offers absolute time for any factory all over the world. Wherever the location, the 1 microsecond accuracy is maintained.
Typical applications where high level of time synchronization is required:
high speed, on line, 3D laser digitalization
high speed assembly lines (automotive, health care…)
igh precision processes managing various data like metal stamping (distance control, speed, acceleration…)
high and medium voltage station control
Redundant ring network and time redundancy
The T208 Ethernet switch benefits from the performance of the Westermo U/R/T200 range re-configuration time of only 30 milliseconds. Several redundant rings of industrial Ethernet switches can be connected, creating full link redundancy throughout the whole industrial application. Concerning time redundancy, the nodes will use the time served from the best server and, should one drop out, the nodes acquire time from the next best available. GPS redundancy is obtained in the same way by using multiple GPS receivers.
Technical information:
GPS synchronized time server
GPS receiver interface supports RS-232 or RS-422
Satellite signal failure highlighted via SNMP
NTP/SNTP server integrated in switch
Compliant with RFC1305 and RFC2030
Accuracy better than 1.0 ìs
Accuracy independent of network load
Free running clock
Time reference from external GPS or internal clock
30ms reconfiguration of redundant ring
WESTERMO TELEINDUSTRI AB, a Swedish company created in 1975, is a European leader in industrial data communication.
Key numbers:
three subsidiaries: France, Germany, UK
distributors in more than 30 countries
100 employees
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