SCADA & HMI

Tag quality

Definition

An indicator on a SCADA value saying whether it can be trusted, alongside the value itself and a timestamp.

When a remote site stops answering, its last known level does not become wrong, it becomes stale. A display that renders a stale value normally has caused more bad operating decisions than almost any other defect.

Also known as: bad quality, data quality.

Bad QualityWhat a quality flag means and where it comes from: good, uncertain, and bad with substatus codes, how quality propagates from device through driver, tag, display, alarm, and historian, the causes by layer, and the rule that a bad value is never a number.

Tag quality

Definition

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