Spot a fake DS18B20 on a Raspberry Pi: family-code check, sysfs CRC test, and ice/boil calibration against the datasheet. 3 of 7 probes in one batch were counterfeits, drifting 1.5–3.5 °C.
CT clamp burden resistor calibration for ADS1115 on Raspberry Pi: pick the external burden, stabilise with a decoupling cap, and apply the DC-bias correction that separates a stable watt reading from drift — with the 51 Ω + 10 µF combination I actually measured.
DHT11 accuracy after 18 months of continuous logging on a Raspberry Pi: 26,318 rollup rows, 38% below the datasheet's 20 %RH floor, and where the part stops being usable.