Power monitors

High-side I2C power monitors, Hall-effect boards and clamp-on CTs answer different questions: rail telemetry, isolated DC/AC current, or mains measurement without breaking the circuit.

INA-series I2C monitors, Hall-effect sensors like the ACS723 and Gravity 20A/50A boards, and non-invasive CT clamps for everything from 3.3V rail telemetry to mains current sensing.

• INA219 (26V, ±3.2A) is the classic I2C shunt monitor; INA237/INA238 push to 85V with a 15 mΩ shunt, INA228 adds 20-bit resolution, INA260 has its shunt built in, and INA3221 watches three rails at once — most on STEMMA QT/Qwiic boards.
• Shunt monitors sit in-circuit and share a ground reference; Hall-effect parts (SparkFun ACS723, Gravity Analog 20A and 50A AC/DC boards) add galvanic isolation and handle AC, at the cost of analog output and zero-offset drift.
• For mains, Seeed's non-invasive CT clamps (25A, 60A, 100A) snap around a single conductor without touching live wiring — but they are current transformers, so you get a raw AC waveform to scale and RMS-process yourself, not a calibrated reading.
• Readouts and conditioning live here too: 0.28-inch LED DC voltmeters, 10A/50A LED current meters, DFRobot's Gravity I2C Digital Wattmeter and a 4–20 mA current-to-voltage converter for industrial loops.