Flatline Rule

Type: flatline — Built-in check; no custom expression.

What the rules engine does

The flatline rule flags sensors that are stuck — the value does not change (or changes very little) over a rolling window. The engine computes the rolling spread (max − min) over window samples. When the spread is below tolerance, a fault is flagged. This catches dead sensors, frozen readings, or communication dropouts. Inspired by SkySpark-style hisRollup(spread, timeSensitivity) < tolerance.

sensor_flatline (flatline)

Stuck sensor — value does not change over window.

name: sensor_flatline
description: Fault if sensor value does not change over window (stuck sensor)
type: flatline
flag: flatline_flag

inputs:
  Supply_Air_Temperature_Sensor:
    brick: Supply_Air_Temperature_Sensor
    column: sat
  Zone_Temperature_Sensor:
    brick: Zone_Temperature_Sensor
    column: zt

params:
  tolerance: 0.000001
  window: 12

weather_temp_stuck (flatline)

Temperature sensor stuck at near-constant value. Common for weather stations.

name: weather_temp_stuck
description: Temperature sensor stuck at near-constant value
type: flatline
flag: fault_temp_stuck

inputs:
  Outside_Air_Temperature_Sensor:
    brick: Outside_Air_Temperature_Sensor
    column: temp_f

params:
  tolerance: 0.2
  window: 6

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