ATMEGA328p Standalone 8MHz @ 2.5v

Well of course the 'burden' of the fixed shunt resistance of the amp meter will have an effect on the actual voltage applied to the load being measured. It forms a simple voltage divider with the load resistance and follows ohms law. A simple 'fix' is to simply measure the voltage actually being applied to the load with a second meter and adjust the source voltage for the value you wish the load to be operated at as you measure it's current consumption at that applied voltage.

Understanding ones basic test equipment is important if you want to account for all the possible sources of variation and error in taking precise measurements, if that is indeed the task at hand.

Lefty

The particular meter that David Jones was talking about has a equivalent resistance of 1.8ohm (1.8mv/ma), in the 200ma current setting.

As the current we are talking about here in this threads are on the tune of 2ma, the "burden" induced by the meter is 4mv, or about 0.1% of the supply voltage.

I think the avrs can deal with that without any problem.