Power meters are installed in every house. This is how supply companies know how much to charge you for electric energy you have used. But if like to experiment with electronics devices probably you’re curious how much energy they take. IT doesn’t matter if device is battery operated, or powered from mains.
Koltykov has built pretty simple power monitor device based on Arduino. It is capable to measure up to 2A and 12V. Power meter uses current sense monitor chip ZXCT1010. It produces a voltage relative to current sensed on “Sense” resistor.
Voltage is scaled down with simple resistor divider. Voltage and current levels are fed in to Arduino analog inputs. Arduino Nano V3 takes care of calculating the actual values and displaying them on Nokia 5110 LCD display. Arduino is rich in code libraries, so it took only few lines to get it working.