An essential for any electrician - Socket and See's SOK34 both tests a socket's internal wiring to find faults, and also performs full loop tests!
The SOK34 is extremely easy to use - just plug it into the socket you want to test and if there's an issue with the internal wiring, the SOK34 will let you know about it by using a combination of LED and audible tone indicators. Unlike many other similar socket testers available on the market, the SOK34 also has the added benefit of telling you exactly which element of the wire is causing a problem (earth, neutral or live), complete with easy-to-follow guide on the front of the tester.
This socket tester also performs a full true check of earth loop impedance; it uses a combination of three coloured LED indicators to tell you if the loop test is good (green), needs checking (yellow) or needs an urgent check (red).