Introduction for Ground Continuity Test

1. Importance of ground continuity test

Nowadays, the manufacturers of electric and electronic equipment must try best to ensure the safety of the user, and protect the user from electric shock even any fault operation. To reach this public requirement, ground continuity tester must be applied. At the moment, most electric safety execution institutions like UL, CSA, IEC, BSI, YDE, TUV and JSI are requires the manufacturers to do the ground continuity test during the design and production periods.   

2. The AC ground continuity test

Ground continuity tester‍ is applied to test the resistance between earth cable and enclosure according ohm law. Current flow through contact point, test the voltage values of current and contact point separately, then calculate the resistance value according to ohm law. Generally, flow through a big current, the abnormal current caused by simulator under abnormal conditions would be the test standard. If the contact resistance of ground cable can pass the test under bad conditions, the equipment should be safe in the normal conditions. The electronic equipment must do the AC ground continuity test with the following conditions:

a) Function test during the design--- To ensure the new product can reach the demand.

b) Specification test during production--- To ensure the finished product can meet the requirement.

c) Quality test during QA--- To ensure the quality can meet the standard requirements.

d) Safe test after maintenance--- To ensure the product can meet the standard requirements after maintenance

Different products have different technical specification, basically, it would requires a constant current flows through contact point, and keep for a certain time. For example, the resistance of contact point keeps in the normal range during the specify time, then the equipment would be thought as safe when operate in the normal condition. Reasonable design can protect the user from dangerous of accidental electric shock.

Although the contact resistance can be tested by ohmmeter, the ohmmeter can only output small current, which can not meet the standard requirement, and can not be accredited by inspection institutions, ground resistance meter is a must tool. For electronic equipment can often be touched, 30 amp is required by CSA to do the ground resistance test, 25 amp are required by most institutions, like UL, BSI, TUV, VDE and etc. and the resistance of contact point must be lower than 100 mΩ, current must keep for 60s and resistance must keep below 100 mΩ. For electronic equipment can be hardly touched, generally, it will requires 10 amp and resistance must keep below 100 mΩ, and still keep for 60s.

Internationally, some specification would higher than standard, the rated input current requires 5 times of the standard, and resistance of contact point should be 100 mΩ and keep for 60s. Mostly, the motor requires the more strictly test. At the moment, for special demands, ground resistance test should be the priority, the dielectric withstand voltage and insulating resistance test should be done upon pass the ground resistance test.

The ground resistance test has two types, AC and DC, although both type are allowed, but AC ground continuity test is especially recommended.

Pego is specialized in electric safety test equipment, recently, we have ground resistance tester, withstand voltage tester, insulating voltage tester, leakage current tester, LCR meter and DC electronic load.