deadband

A Historian for PLC Data: What to Log, How Often, and What Compression Costs

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A six-row table of 1200 tags grouped by class, with the tag count, data type, collector rate, raw events per day and the logging policy each class earns, from 180 analogue process tags through counters and state words to 660 bools and 60 batch-record tags at a fixed one second

1200 tags collected once a second is 160,704,000 values a day, and at the 12 bytes a historian typically spends on a timestamp, a value and a status that is 1.93 GB a day and 704 GB a year. The same 1200 tags, with a deadband at the collector and a compression test at 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

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