Glossary
What is Alarm deadband?
A gap between the value that raises an alarm and the value that clears it, so the alarm does not chatter around the trip point.
For example: the alarm raises above 85% and clears only below 83%. A 2% deadband is enough to stop dozens of alarms from a noisy measurement.
It is used together with an on-delay timer: the delay filters fast noise, the deadband filters slow drift across the limit. Both come from ISA-18.2.
Related terms
- On-delay timer (TON)
- A standard function block whose output Q becomes true after IN has stayed true for PT without interruption, and resets as soon as IN drops.
- ISA-18.2
- The alarm management standard for process industries: the alarm lifecycle from design to review, and the alarm rates considered acceptable.