13A Test Plug With Earth Loop Impedance
The Earth lmpedance Test Plug by Martindale has all the features of the basic plug plus additionally it will tell you how safe the earth is without tripping any RCDs, and if the voltage is correct. The impedance is measured within one of six ranges from 0-1.7 ohms to 200-500 ohms. A value of over 500 ohms will produce a fault indication. This is a must for any toolbox now.