Earth conductor resistance testers

Electrical products are typically connected to the power supply via power cords with plugs or terminal blocks. The protective conductor test is therefore performed between the PE terminal of the plug or terminal block and all connected metal parts of the electrical product’s housing.

If multiple metal housing components in an electrical appliance are connected to the protective conductor, the proper functioning of the protective conductor must be verified individually for each housing component. If protective conductor connections are no longer accessible on the fully assembled electrical appliance, these connections must be tested during production as part of interim inspections.

The protective conductor test detects these faults.

• Interrupted protective conductors
• Protective conductors with too high an impedance, poor contact resistance
• Loose connections or poor contact points in the protective conductor

How is the protective conductor tested?

In most cases, the protective conductor is tested based on its measuredohmic resistance. Alternatively, the voltage drop across the protective conductor can also be measured.

To determine the resistance or voltage drop, a high minimum test current must flow through the protective conductor, depending on the test standard. The test device sets the test current to the specified level and regulates it to a constant value.

The high test current is intended to simulate a load on the protective conductor in order to "burn away" any weak connections that may be present. However, with typical test durations of one second, this usually does not succeed in practice, as it is virtually impossible for the contacts to heat up enough to burn away the weak connections within that time.

Thefour-wire method(also known as Kelvin measurement, 4L, or 4W) is extremely important for precise protective conductor testing. It is the only reliable way to accurately measure smallresistances in the milliohm range. The tester therefore uses four-wire technique to determine the voltage drop across the protective conductor and calculates the protective conductor resistance based on Ohm’s law.

The "good/bad" criteria.

Standards define upper limits for ohmic resistance or voltage drop. These limits must not be exceeded under any circumstances.

Should the protective conductor be tested with AC or DC?

In most cases, the test current is alternating current. However, in some applications—such as when using long coiled connection cables—direct current can also be advantageous.

This is how the protective conductor test is performed.

Whether manual, semi-automatic, or fully automatic: with SCHLEICH's protective conductor testers, any testing task can be performed quickly and efficiently.

All of our testers are designed according to the "KISS principle"—that is, following the motto:"KeepIt Simple and Smart."This principle serves as the guiding philosophy for all SCHLEICH products!

A manual test is performed using an earth conductor test probe. To do this, the operator moves the test probe by hand from test point to test point. Despite the manual process, the test can be fully documented. A typical application is the inspection of electrical products, control cabinets, and machines in accordance with the Machinery Directive EN 60204.

For the needs of manufacturing facilities, semi- or fully automated protective conductor testers or automatic protective conductor testers are ideal. These testers are equipped with a relay switching panel (relay matrix), which automatically routes the test currents to the desired test points.

Depending on the application, test systems of this type can have up to 1,000 test ports.

Requirements for a standard protective conductor tester.

Many national and international standards requiretest currents ranging from 10 to 30 A. These test currents can be set in steps on the tester. In addition, SCHLEICH also offers protective conductor testers with test currents ranging from1 A to 500 A AC/DC.

SCHLEICH protective conductor testers are based on over 30 years of experience. From the very beginning, the measurement technology has been digital rather than analog. We always use state-of-the-art technologies.

Here's how to find the right protective conductor tester.

There is a wide variety of protective conductor testers available on the market, and the number of configurable features is overwhelming.

If you intend to perform only AC or DC protective conductor tests on your test object, a single-function tester is the best choice. It supports only the "protective conductor resistance" test method.

If the test object also requires a more comprehensive safety and functional check, we recommend our combination testers/multifunction testers. These allow you to conveniently combine various test methods—such as protective conductor, insulation, and high-voltage testing—into a single device. The fully automatic test method switching integrated into the tester ensures that no test leads need to be manually reconnected to the test object during the test.

In addition, it is common to find a combination of safety tests and comprehensive functional tests. For functional testing, the test device also supplies the test object with operating voltage in order to verify its electrical performance characteristics.

Thanks to the intuitive and user-friendly operation of SCHLEICH's protective conductor resistance testers, every test is performed quickly, accurately, and cost-effectively.