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Using A Clamp-on Ground Meter To Test Ground Rod

Update:19 Dec 2018

A ground rod is an important part of an electrical syst […]

A ground rod is an important part of an electrical system. It allows uncontrolled electricity to go to the ground instead of causing a fire or damaging a building. When installing a ground rod, you need to make sure that electricity will easily flow through it into the earth. The resistance to the flow of electricity is measured by a ground meter and is read in ohms. The lower the number of ohms of resistance a grounding system has, the better your protection is.


Get a clamp-on ground meter. A clamp-on ground meter is a specialized electronic machine that checks electrical resistance. These meters can range from about $100 (USD) to over $1500 for professional models. They are available at hardware stores, home improvement stores, and online retailers of electrical supplies.


The clamp-on meter will give you a reading in "ohms," which is the unit of measurement for resistance. It may be signified with the symbol "Ω" on the meter.


Clamp the meter on the ground rod or grounding electrode conductor. Open the clamp by pressing the lever on the side of the meter and holding it down. Then put the clamp around the grounding electrode conductor or the top of the ground rod. Let the clamp close by letting go of the lever.


The meter should be used as close to the ground rod as possible. Using it further down the electrical system, such as near the electrical panel, will read other ground sources in addition to the ground rod.


Turn on the meter. How you start the meter depends on the specific brand you have. Some simply have a button that says "power" or "on." Others have a dial that needs to be set to ohms.


If you are unsure of how to turn on your ground meter, follow the directions included with it.


Assess the readings on the meter. Your clamp-on ground tester will have a screen that will show you a numeric reading. The lower the number on the meter, the better your grounding rod is working. In general, a reading under 25 ohms means that your ground rod has a good connection to the earth.