Power Measurement & Instrumentation#

Estimating power consumption from datasheets and calculations is a starting point, but real embedded systems behave differently under real firmware. A peripheral left enabled after initialization, a pull-up resistor sinking current through an unused bus, or a radio that never fully enters sleep can each add milliamps that do not appear in any schematic review. Accurate power measurement — with the right tools and the right measurement architecture — is the only way to verify that a design meets its energy budget.

Current sensing methods range from a simple shunt resistor and oscilloscope to dedicated power analyzers that capture microamp sleep currents and hundred-milliamp transmit bursts in the same trace. In-circuit monitors like the INA219 and INA226 provide continuous measurement over I2C, enabling firmware-driven power logging without external instruments. This section covers the full instrumentation chain: sensing architectures, dedicated analyzer tools, and embedded current monitors.

What This Section Covers#

• Current Sensing Methods — Shunt resistors, sense resistor selection, and the basic measurement circuits behind every power measurement.
• High-Side vs Low-Side Sensing — Architectural tradeoffs and current-sense amplifier ICs (INA180, INA213) for each topology.
• Power Analyzer Tools — Nordic PPK2, Otii Arc, Joulescope, and Keysight N6705C workflows for characterizing embedded power consumption.
• In-Circuit Current Monitoring — INA219/INA226 I2C configuration, register setup, alert thresholds, and firmware logging patterns.