A current probe. You might need more then one probe for instance you might have one current probe that was accurate at a lower current but could not measure th

A current probe. You might need more then one probe for instance you might have one current probe that was accurate at a lower current but could not measure the higher current, and a second probe for the high current. Then process the data using the appropriate instrument depending upon the current. I haven't done much w/ AC power measurements, but it's a common enough problem (large dynamic current range) for DC power measurements. Agilent (now Keysight) make instruments like the N6705B DC Power Analyzer that can sample a pretty high rates (like 10's of uSeconds) and be accurate at both uA range and 100's of mAs for dynamic current. I would imagine you could rig up something similar for AC power measurements.