Accordingly to your informations, can I use something like this: http://www.melexis.com/Hall-Effect-Sensor-ICs/Linear-Hall-ICs/Programmable-Linear-Hall-Effect-Sensor-85.aspx with a split toroidal core (like this: http://cpc.farnell.com/1/1/1608-split-toroidal-core-7-50mm-rrc16-08-16m-richco.html) around the electric cable to get what I want ?
I prefer to learn and do things by hands 