4.1.2-4 Parameter Stability Processing

The alarm system should incorporate the capability to apply time filtering, time delay, or deadbanding to the alarm inputs to allow filtering of noise signals and to eliminate unneeded momentary alarms.

Additional Information:
Noise from plant instrumentation may result in signals that momentarily exceed the limit for alarm message activation for a plant parameter. Time delay processing prevents this signal from generating a spurious alarm message to the crew. In some cases, applying these techniques may reduce the timeliness of the information provided to operators. When this tradeoff is not acceptable, other processing methods can be used (see additional information for Guideline 4.1.1-3).