You need a Wattmeter to measure AC Adapter current under varying conditions.
There are reasonably economical wattmeters available.
Battery threshold is normally 80% (versus fully charged), so at 80 or 100% charge, the AC Adapter current draw will be about the same, and will be related more to computer load.
A wattmeter can help you here.
It will show average levels more than instantaneous levels, depending on the dampening within the meter. You may want a meter with a low power range to see your power level more clearly (a 100 watt Wattmeter won't show you much).