Dear Hi, 1. If you test in Yellow Taparia cum screw driver you can't ensure Earth 2. Its better to ensure with Multimeter for Earth Measurement 3. You can see this in below link : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-pl_CjHb4Ojk.html Thanks