kepware

OPC DA to OPC UA: What Changed, and the Tunneller You No Longer Need

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The path of one OPC DA read drawn as six boxes: SCADA client calling IOPCSyncIO Read, the COM runtime marshalling with the caller identity, TCP 135 as the RPC endpoint mapper, a second connection to a dynamic port above 49152, the DA server executable and its account question, and the EtherNet or IP driver to the controller

OPC DA to OPC UA: What Changed, and the Tunneller You No Longer Need KB5004442 stopped being optional on 14 March 2023, and with it went the last registry value that could keep an OPC DA link alive between two Windows machines. RequireIntegrityActivationAuthenticationLevel is still sitting under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole\AppCompat on every machine somebody set it on, … Read more

Good Quality, Stale Value: Diagnosing an OPC Link That Is Lying to You

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Five boxes in a row from the controller through the driver, the server cache and the subscription to the client, with four numbered red break points marked underneath

Seal_Temp has read 182.4 °C since about 04:00, the quality field next to it says Good, and the trend behind it is a flat line eleven hours long. The bagger has run four product changes in that time and the seal jaws are visibly hot. Nothing on the SCADA is in alarm, nothing in the … Read more

Scan Rates, Scan Groups and the Deadband That Halves Your Traffic

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A four-column table listing the controller task, the device Scan Mode, the tag Scan Rate and the client group rate against what each controls, its range and when it wins, with the device Scan Mode rows highlighted

A SCADA client on the TR-14 line subscribes to 1180 tags in one group at 250 ms, which people write down as 4720 value updates a second. Over an hour the server actually delivered 3,832,580 notifications, and 3,744,000 of those came from 260 analogue tags, most of which were sitting still. The 920 digital and … Read more

Kepware with a ControlLogix: the Tag Import, the Arrays, and What Breaks

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Five boxes in a row from Studio 5000 through the import route, the server group and the server tag to the client item, with four numbered red points marking where each join fails

Automatic tag generation against one 1756-L83E produced 5537 server tags in about ninety seconds, and the clients on that site reference 684 of them. The other 4853 are array elements nobody reads, structure members nobody reads, and a full PID_ENHANCED nobody has looked at since commissioning. They cost project load time, they cost browse time … Read more

Kepware Channels, Devices and Tags: the Structure to Get Right Before the First Tag

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Five boxes in a row showing one value walking from the controller through the channel, the device, the tag group and the server tag, with four numbered red points below marking where the chain breaks

A SCADA client stores one string for every value it reads, and on the line I am about to describe that string is CLX_Line1.Bagger.Infeed.Belt1_Run. Four names, each chosen by a different person on a different day, and 684 more strings on that one device built the same way. Rename the tag group on a Friday … Read more

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