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

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

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