Ground Bond Testers Information
Ground bond testers are electrical safety test devices that perform electrical compliance tests. Ground testing is mandated on all electrical and electronic devices by a variety of compliance standards bodies to ensure that persons coming in contact with the devices will not be injured due to shock or electrical discharge.
The two most common types of ground bond testers are those that test for:
- earth continuity (EC)
- ground continuity (GC)
In general, when someone speaks of ground bond testing, they usually are referring to earth continuity testing. Earth continuity ground bond testers are used to verify the integrity of the ground connection between the power cord and exposed metals in high current devices and applications. This is achieved by measuring the resistance between the exposed metal parts and the ground blade of the power cord. These devices only use an AC test signal, which functions at a line frequency of 50 or 60 Hz, testing devices that are less than 12 V, and have current level ranges from .1 to 60 amps. For a device to be certified safe, the resistance should be measured at less than 1Ω. Most European standards such as TUV, IEC, VDE, BABT, and CSA require this type of testing.
Ground continuity ground bond testers verify that connections between conductive wiring and grounded power cords are safe, and that even exposed wiring poses no threat. This style of test can be performed using either AC or DC test signals, but is usually used in conjunction with devices that function at low power levels. AC signal testers generally function using less than 1 Amp, while DC testers simply check the grounding between exposed metal and the ground. However, DC testers are not designed to test the integrity of the ground, only that there is one.
Underwriters Laboratories (UL) requires ground continuity testing on all electrical devices manufactured with cords that are sold in the U.S.
Ground bond testers are available in three main testing forms: automatic, semi-automatic, and manual. Automatic ground bond testers can perform their function with no human interaction. They may also have the ability to perform a series of electrical safety tests. Semi-automatic devices require some human interaction, but are generally capable of performing the required tasks in-situ. Manual testing devices require that an operator be present to make physical changes to the test parameters as needed.