https://www.google.ca/search?biw=1440&bih=787&tbm=isch&sa=1&ei=oB3SWqyZKOSMjwTkvpuIDg&q=toroidal+current+sensor&oq=toroidal+current+sensor&gs_l=psy-ab.3..0i24k1.23167.31870.0.34420.14.5.0.9.9.0.98.416.5.5.0....0...1c.1.64.psy-ab..0.14.466...0j0i30k1j0i10i24k1.0.LHdXy93AHQw
use toroidal current sensor, primary 2 turns secondary 10 turns - for current