Reading the physical world.
WHAT COMMON SENSORS MEASURE
Temperature and humidity Light Motion and presence Position and orientation Distance and proximity Pressure Current and voltage Flow and level Gas and air quality Sound
WHAT SPECIFICATIONS MATTER
- Range: what values it can read
- Accuracy: how close to true
- Precision: how repeatable
- Resolution: the smallest change detectable
- Drift: how much accuracy degrades over time
WHY DRIFT MATTERS MOST IN DEPLOYED SYSTEMS
Readings slowly become wrong, and nothing indicates it.
WHAT TO PLAN
Calibration, or replacement.
WHAT CALIBRATION REQUIRES
A known reference, and a procedure.
WHAT TO RECORD
When each device was calibrated, and against what.
WHAT NOISE IS
Random variation in readings.
WHAT REDUCES IT
Averaging over samples Filtering Better placement
WHY PLACEMENT MATTERS ENORMOUSLY
A temperature sensor in sunlight measures the sunlight.
WHAT TO TEST
Readings against a trusted instrument, in the actual deployment position.
