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Offline Anders Eriksson  
#1 Posted : Tuesday, October 4, 2016 2:26:56 AM(UTC)
Anders Eriksson

Rank: Newbie

Joined: 3/18/2016(UTC)
Posts: 4

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We are using MatrikonOPC UCS with Modbus and Mitsubishi plug-ins (different machines).

We are subscribing to a number of tag (not many, 5 integer and 5 strings)

What would a reasonable value for the Update Rate be?

1 ms, 50 ms, 200 ms ???

Also does the Update Rate effect the time it takes to write a value?

We have set the Update Rate to 50 ms.
The communication is set so that when the PLC change a value, we check which tag is changed and reply to a reply tag with the same value. If these two values are different something is wrong with the communication.

Unfortunate the time from that the PLC sets it value and the client reply is almost a second!
The time is "the same" with both integers and strings.

Any ideas on what may be wrong? (or is this how OPC works...)
thanks 1 user thanked Anders Eriksson for this useful post.
Offline Roger Fortune  
#2 Posted : Sunday, October 9, 2016 10:59:27 PM(UTC)
Roger Fortune

Rank: Advanced Member

Joined: 10/21/2014(UTC)
Posts: 105

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OPC is not normally used for sub-second critical data. Generally, an update rate of 1000mS is acceptable and widely used. Sometimes customers will push to 500mS or faster. It is sometimes possible and I have seen update rates as fast as 200mS, when the underlying communication (between the OPC Server and device) is robust and fast. Our software is set to reject any requests faster than 100mS as it is generally not possible. In the case of the UCS, I would not recommend anything less than 500mS.
thanks 1 user thanked Roger Fortune for this useful post.
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