Maintenance

Every conclusion here rests on hardware that degrades. An electrode calluses over, a soil probe corrodes, a serial link drops.

The failure that matters is not the loud one. A driver that throws gets caught and reported. The dangerous case is a component that keeps answering while being wrong — a stuck humidity sensor reads 55% all week, the plant looks stable, the VPD calculation is confident, and every layer downstream reasons beautifully about a number that stopped being a measurement days ago.

stuck sensor → degraded

  mock [degraded]
     humidity: The last 28 readings are all exactly 55. A real measurement moves
     in its last digit even in a still room; this sensor has latched.

what to do about it:
  · Sensor "mock" is unreliable; readings from it should be treated as suspect.

suggested evidence weights: { "mock": 0.25 }

Checked	How it is caught
Stuck sensor	Exact equality, repeated. A stable room still moves the last digit; a latched sensor does not
Impossible readings	Values outside what the metric can physically be
Flat electrode	Living tissue is never electrically silent, so silence is the wire, not a calm plant
Mains hum	Power still at 50/60 Hz after filtering — grounding, not physiology
Aliased sampling	A rate at or below 2× mains folds the hum down into the plant's own band, wearing a plausible frequency
Saturation	An amplifier pinned at its rail reports numbers without measuring
Tiring contact	Reuses the continuity verdict rather than inventing a second opinion
Driver failures	Consecutive and proportional failure rates per driver
Memory	Readings out of chronological order break every window and trend computed from them
Colony link	Neighbours that were reachable and no longer are
Body	Safety limits refused repeatedly — the layer above keeps asking for what it cannot have

Nothing is quietly discarded. A component judged unreliable is marked unreliable, its suggested evidence weight drops, and the reason is stated — because silently dropping a sensor is its own way of being wrong without saying so. Faults are filed as claims about the instrument (instrument_unreliable), so a conclusion can be discounted when the thing that produced it is broken.