Earthing resistance tester is used for measuring internal earthing resistance of electrical equipment, which reflects the (contact) resistance between exposed conductive part at each position of electrical equipment and general earthing terminal of electrical equipment. Earthing resistance tester uses 4-end measurement method in order to eliminate the influence of contact resistance to test, namely, a current (generally about 25A) is applied between the exposed conductive part of tested appliance and general earthing terminal and the voltage between these two ends is then measured and its resistance value is calculated.
Eason Wang