Earth resisitance can be measured using megger or earth tester and thr resisitance of proper earthing must always be less than 10 ohms and for sensitive installations such as very sensitive communication and computer systems about 2 ohms is recommended.
Earth resistance is measured by means of earth tester or megger. The earth resistance must and should be less than 0 to 5 ohms. If it is above the 5 ohms we say earth resistance is not good.