Megger ltw425 2 wire non tripping high resolution loop tester megger ltw425 eu sc the megger ltw425 high resolution loop tester is a two wire earth loop tester which can verify the loop impedance of a live electrical circuit without the need to disconnect the electrical supply it offers a range of features to make earth loop testing safer and easier a loop test is performed with only 2 test leads either phase to earth phase to neutral or phase to phase testing is simplified by the lack o