Hi Riya,

It is very easy to interface a CT for current measurement. A CT produces a current signal [i] across its terminals and this current signal [i] is directly proportional to the current being measured [I] i.e. the current flowing through the conductor that has been passed through CT hole.
i=I/N
iαI

For using a CT you put a resistor across the CT terminal this resitor produces a votlage across its terminals.
v=iR.
since R is constant and iαI
thus vαI.

Take care that the resistor value you choose produces maximum voltage meausred by ADC when the maximum current flows through the conductor being measured. Also choose an appropriate wattage resistor else you will end up blowing the resistor.

Measure the voltage produced across this resistor this gives you instantaneous current through conductor. To find the effective or RMS current you should take as many samples from ADC as possible.

For Example:
Take say 200 samples per cycle i.e. 20ms if your power frequency is 50Hz. Thus you are sampling ADC every 100uS. and thus you end up with 200 ADC values i1, i2, i3, i4, .... i200
Find squre of each sample and add the sqare values you get sum of sqares. Now divide this sum of sqares with number of samples ie.
200 in this case and you get Mean Square Current.

Mean Square= (sqr(i1)+sqr(i2)+sqr(i3)+....+sqr(i200))/n

Now find out the square root of mean square and you get Root Mean Sqare current or Effective current.

RMS current = sqrt ( Mean Square )

Regards,
Prahlad Purohit