REQ-005 — Per-channel current sense via INA2181A1 across 500 mΩ shunt (external ADC)

Each channel shall sense its output current using an INA2181A1 current-sense amplifier (gain 20 V/V) across a 500 mΩ shunt. The amplified analog output is digitized by an external ADC — the module has no on-board ADC (see REQ-010). Full scale: 500 mΩ × 500 mA × 20 V/V = 5 V.

Each channel's sensed output (via INA2181A1) tracks actual output current across 0–500 mA. Measurement accuracy is bounded by the INA2181A1 (gain error + offset) plus the external ADC resolution. TBD — final accuracy figure from the INA2181A1 datasheet error budget.