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. A clamp-on meter allows you to check the resistance of an installed ground rod without disconnecting it from the electrical supply. [3] X Research source Working with electricity can be dangerous! If you don’t have the right tool or aren’t sure how to use it, contact an experienced electrician or lineman for help.
Clamp the meter near the ground rather than at the top of the rod.
Using an earth electrode tester instead of a clamp-on tester will take a lot more time and effort. If you have the option of using a clamp-on meter instead, do it.
The ground probes are typically about 1 foot (0. 30 m) long. They should be inserted into the ground until the top of them is just visible. The leads that come with earth electrode testers are typically very long, so they should reach the required distance.
In general, it doesn’t matter which lead goes to which ground rod or probe. However, the lead for the furthest ground probe should be the longest one so that it will reach.
If a ground rod has a good connection to ground, its reading should be a number below 25. [9] X Research source
To ensure that your ground rod is sufficient, the average of all 3 readings should be less than 25 ohms.
Most electrical systems also have secondary grounding means, such as the grounding bar being connected to a cold water pipe that goes into the ground. Make sure that the secondary grounding means is also securely connected.
This may not require you to put a ground rod a long distance away from the original rod. Even a few feet can make a difference for the ground resistance.
Your second ground rod should be located at a distance that is equal to the length of your ground rod. For example, if your first ground rod is 8 feet (2. 4 m) long, your second ground rod should be located 8 feet (2. 4 m) from the first ground rod.
