Rockwell Automation T8030S Trusted OPC Server Package - Manual (Page 23)

Trusted
TM
OPC T8030S
Issue 23 April 10 PD-T8030S 23
Using a low bandwidth connection (e.g. radio link, multiplexed fibre connection) will reduce the number
of messages per second.
The number of ordinary messages is often too complex to calculate with any precision. Normally the
easiest way to set up the poll rates is to set the Ungrouped Tag Update Rate (global poll rate) to the
slowest acceptable update rate. Then set the SOE and Process Historian poll rates as fast as
possible, but without overloading the communications link.
Examples:
All Tags collected by Sequence of Events and/or Process Historian
Global Ungrouped Tag Update – Should be set to a high value (e.g. 10000 ms (10 seconds)) so that
accidentally configuring a non-SOE/PH Tag in the future will not compromise the server
communication link.
Process Historian Update and Sequence of Events Update – The combined poll rate should not
exceed 12 polls per second. If both are used they should be set to 166 ms or higher, if only one is
used it should be set to 83 ms or higher and the other should be unchecked.
No Tags collected by Sequence of Events or Process Historian
Global Ungrouped Tag Update - Set to the required update rate. The server will attempt to refresh all
ungrouped tags at this rate, provided it is less than the maximum achievable transfer rate. The
maximum transfer rate achievable per second is approximately 5000 16-bit Analogue variables, or
2500 32-bit Analogue variables, or 35000 Boolean variables. This requires all the variables to be
configured with consecutive communications addresses. Any other configurations of communications
addresses or combinations of the data types will affect the maximum achievable transfer rates. Setting
the rate to 1000 ms (1 second) would allow this number of variables to be read, setting the rate to 2000
ms (2 seconds) would allow double this number of variables to be read.
Process Historian Update and Sequence of Events Update – These should be unchecked for this
example.
Only Some Tags collected by SOE / Process Historian
As the normal polling and SOE/PH polling share the bandwidth, the poll rates for both have to be
reduced. The best polls rates can only be determined by tuning the poll rates with the final databases.
Typically in one second it is possible to do three SOE polls, three Process Historian polls, and have
sufficient bandwidth available to read approximately 2500 16-bit Analogue variables, or 1250 32-bit
Analogue variables, or 17500 Boolean variables (assuming that they have consecutive
communications addresses).