This non-invasive current sensor (also known as a "split-core current transformer") can be clamped around the supply line of an electrical load to tell you how much current is passing through it. It does this by acting as an inductor and responding to the magnetic field around a current-carrying conductor. By reading the amount of current being produced by the coil, you can calculate how much current is passing through the conductor.
The difference between this and other conventional Sensors is that using this sensor you need not cut wire to measure its current. Just clamp it and you are good to go.
SCT 013-050 Current transformers (CTs) are sensors that are used for measuring alternating current up to 50 Amperes. They are particularly useful for measuring whole building electricity consumption (or generation for that matter). These are particularly suitable for DIY use, it can be clipped straight onto either the live or neutral wire coming into the building without having to do any high voltage electrical work.
This non-invasive current sensor clamped around the supply line can measure a load up to 50 Amps, and allow you to calculate how much current passes through it. It can be useful for building your own energy monitor or for building an over-current protection device for an AC load. This current clamp can be used to detect a current of up to 50A. Simply clip it around the current source that you wish to measure and it will produce a (very) small AC voltage proportional to the current. The cable is terminated on one end with a standard 3.5mm jack (like a headphone jack). Use this to build your own energy monitor and keep your power usage down or use it to build an over-current protection device for an AC load.