electrical safety -ground testing

Together with the development of new instrumentation, the test procedure has also been standardized. To "walk" the probe to the probe potential and current graphs of the measurements, the end user could develop a profile that reliably indicated the ground electrode resistance. This test procedure is otherwise known as the "Fall of potential" method and is described by ANSI / IEEE "Guide for measuring earth resistivity, ground impedance and earth surface potentials of the Earth System" (ANSI / IEEE Standard 81).

Several other popular testing methods, such as slope, 62% Rule, and intersecting curves, were all derived from the fall of potential method (Fig. 1), with slight modifications to deal with specific situations or to improve productivity. However, all these methods use the same instrumentation. The good news is, this equipment has been constantly improved in terms of convenience, safety, ease of use, precision and functionality available.

Stakeless. During the last decade, a new technology entered the market in the form of clamp-on ground testers. This test device was developed specifically to improve the speed and convenience of the ground tests. The potential drop may require labor and time. Even the expedient methods still require units of cord and cable probes. The clamp-on meters represented a quantum leap in terms of convenience. Just strap on a pole on the ground and take a reading. However, this advantage is both an advantage and a disadvantage for the end user.

Properly understood, the clamp-on meters land can be an indispensable tool. But its simplicity may also lead to problems. Many end users tend to clamp around any convenient place and remove the read-without a doubt. Consequently, this method has become unpopular by some in the industry. To be effective, the user of this test equipment must be aware of its operating principle, where it will and will not work, and applications for which traditional methods should only be used.

The clamp-on method (Fig. 2) was derived from the original procedure of "short cut" (ie the "2 points" or "dead land" test method). The connection test is done simply by connecting a piece of test equipment between the electrode and a ground test at a distance, and then measuring a resistance cycle. The method is simple, but loses accuracy, because all the other elements in the cycle are part of the measure. It 'full of danger of inaccuracy, because the remote sensor must be of negligible resistance, which can not be the case. The clamp-on test avoids this problem by relying on multiple return paths, which are parallel with each other. From the law of parallel resistors, the resistance of return virtually cancels out, and the meter only measures the resistance of the soil.