How to Test Ground Rod Resistance

A ground rod.
  • 1 hours
  • Advanced
  • 450
What You'll Need
High-voltage gloves
Clean cloth
Clamp-on Ground Tester

The function of any ground rod is to dissipate the current that is recovered in any faulty electrical circuit near your house to the earth surrounding the ground rod. If you do not have one already, you can easily install a ground rod for your home. The rule is that the lower the resistance it has, the better job it does. However, over time the moisture of your soil, the corrosion of your ground rods, the loss of contact of your wires, and more may increase your ground rod’s resistance. This is why strict monitoring on your part is imperative. The safest way to test a ground rod is by using a clamp-on Ground Tester.

Step 1 - Ensure Safety

Remember that you are going to be working with electricity. You should not take any chances. Wear high-voltage gloves the entire time that you will be handling wires. Make sure that your hands and feet are dry before coming into contact with the ground rod.

Step 2 - Prepare the Clamp-On Tester

The easiest way for you to measure the resistance of a ground rod is to use a Clamp-on Ground Tester. This is a different tool from the Clamp-on Multimeter which only "reads" AC current. The Clamp-on Ground Tester induces the ground rod with an AC signal that is then picked up by a receiving coil within the same clamp and uses the difference to calculate the resistance.

You should visually inspect your Clamp-on Ground Tester. Check the jaws by opening them and closing them. Make sure that the opening and closing mechanism works perfectly. Also, check to see if there is any dirt, dust, grime, or other foreign debris in the clamp jaws and if so, get it off with a clean cloth.

Step 3 - Calibrate the Clamp-On Tester

The next thing that you should do is calibrate your clamp-on tester so that it delivers the right information. Some testers will only require you to set the rotary switch to ohms. Wait for a start-up to finish. Do not open the jaws or clamp the tester to the ground rod while the clamp-on tester is still calibrating. This will totally jar the calibration procedure, making any measurement done afterward inaccurate. Most clamp-on testers will have a calibration countdown that will signify the start and the end of the calibration procedure.

Step 4 - Clamp the Tester to the Ground Rod

When you are done calibrating your clamp-on tester, simply clamp it to your ground rod or to its electrode. You will find the resistance on the display of your clamp-on tester. Make sure that your clamp-on tester’s jaws are fully closed, as a semi-opened clamp will significantly alter the measurement of the ground rod’s resistance. That is why you have to fully familiarize yourself with your clamp-on tester before you use it to measure resistances. An ideal ground rod resistance should be below 3 ohms.

Step 5 - Measure the Ground or Leakage Current

If you wish to find out about the ground or leakage current, all that you have to do is to set the rotary switch to mA or A. Check your clamp-on tester’s manual if it uses another kind of configuration. When you are done with that, simply clamp the tester on to the electrode or the conductor of your ground rod. The ground current or leakage current will be reflected in the display of your clamp-on tester.