Non-invasive AC Current Sensor SCT-013 (100A MAX)

The SCT-013-100 is the 100A current transformer (CT) that is used in the OpenEnergyMonitor project.  The size of the hole (13mm) fits around the main AC lines of the residential homes in Costa Rica.

Datasheet

Instructions on how to make current meter using an Arduino

How a Current Transformer (CT) works