in my project i have to measure voltage and current to calculate power.i can read the analog voltage but dont know to read current.help me out..........
Hello. There are a chip made by allegro that measure current and has an analog signal like output. But there is another cheaper method: you use a 1 ohm resistor and next you read the voltage. 1=y/x y is the voltage and x the current. With this you use the ohm law. Bye
If the A/D converter of the Arduino (10 bit) is not quite accurate enough for your needs so you use an external A/D converter -- the more bits the better. As an example, see page 33 of the MCP3422 datasheet for how this particular 2 channel A/D converter would be hooked up to measure both voltage and current.
The ACS714 is the Allegro chip SUBSEA was referring to. You get 10 bit resolution over a -30A to 30A range.
What typical value of current are you interested in. If several amps then a hall sensor with a 0-5volt output is your best bet.