At present in the electric power system the grounding resistance of the earth network is mainly measured by power frequency large current tripole method. In order to prevent power frequency interference during power grid operation and improve the accuracy of measurement results insulation preventive test regulations stipulate that the test current of power frequency high-current method shall not be less than 30A. As a result there are many problems such as bulky test equipment complicated test process high working intensity and long test time. Ground Network Earth Resistance Tester adopts new frequency conversion ac power supply and adopts microcomputer processing control and signal processing and other measures which well solves the anti-interference problem in the test process simplifies the trial operation process improves the accuracy and accuracy of the test results and greatly reduces the labor intensity of test personnel and test cost. Ground Network Earth Resistance Tester is suitable for testing power frequency grounding impedance contact voltage step voltage power frequency characteristic parameters and soil resistivity of various grounding devices. �© measurable substation ground network (4) water and fire power plants microwave station �© (10) the lightning rod (10 �©) multi-purpose machines. Ground Network Earth Resistance Tester adopts different frequency anti-interference technology which can accurately measure data at power frequency of 50Hz under strong interference environment. The maximum of test current is 3A which will not cause excessive potential of grounding device during the test. Meanwhile it also has strong anti-interference ability so it can be measured without power failure.