How can I measure the current, in a precise way, using an arduino?
Arduino has inbuilt 10-bit ADC which can measure voltage from 0-5 V. If the current to be measured is passing through a known resistor R, hook the nodes of the resistor to two analog pins on the arduino. Use analogread() function to find the two node voltages. Calculate the difference to get the voltage drop across the resistor. Then I = V/R. Calculate it and print the value on the LCD.