Ground

Many sensor field problems look like unstable algorithms, ADC jitter, or poor modules. They often end up being ground and power problems.

The reading is stable when the device is idle, but jumps when a motor starts. Temperature moves during radio transmission. Pressure shifts after a relay turns on. USB power and battery power give different values. Short lab wiring works, while the field installation is noisy.

The physical quantity may not have changed. The measurement reference changed.