The Protective Earth – PE or ground earth test gives actual resistance of ground rod, used as a safety device to protect the machine from sudden unwanted voltage that occurs on different parts of the machine, such as machine body. The ground rod sinks all the voltage safely to the earth, without harm to the humans and causing damage to the machine’s system.

The un-wanted voltage appears on the machine surface or body due to a malfunction in electrical systems such as shorting or losing cables. This condition is hazardous for operators, and sometimes this voltage can also cause death. The un-wanted voltage also affects the machine’s working and can permanently damage the machine’s electrical and electronic components.

To prevent the hazards of this unwanted voltage, the machine is connected to the earth’s ground, which safely discharges the voltage to the ground potential. The resistance ground rod’s resistance must be minimum, ideally 0 Ohm, to avoid any difficulty in smooth discharging.

Additionally, with time, the resistance of the earth’s ground changes due to many reasons such as degradation in rod material, environmental factors and human error.

To check and verify earth ground resistance, Ground Testers are used. They measure the rod’s resistance and, depending upon its result, whether earth ground can be classified as satisfactory or not. If the resistance reading lies in the range, the ground rod is approved for safe operation. If the measured resistance lies outside the range, the ground is no longer classified as satisfactory and corrective actions are necessary to rectify the fault.

Ground Testers induce a high current in the earth rod. The tester’s internal circuitry measures the ground rod’s resistance. The range of satisfactory resistance varies from application to application, but most commonly, it ranges from 0 – 0.2 Ohm. The lower the resistance, the better the ground.