You need to determine the resistance of a grounding rod, in ohms, to know how easily it allows electrical current flow. A resistance close to zero indicates an object that easily conducts current, while a high resistance limits current flow. Ideally, a grounding rod should have a resistance very close to zero to readily transfer electricity from a lighting storm away from your home. A digital multimeter may be used to quickly determine the resistance of a grounding rod.
Connect the red probe to the positive, red port of the digital multimeter. Connect the black probe to the negative, black port of the digital multimeter. Sometimes the negative port is labelled "common." The other ends of the probes contain metal leads for taking measurements.
Turn on the multimeter, then turn the measurement dial by hand to the resistance setting. Resistance is typically designated by the symbol for ohm, which is the capital Greek letter omega.
Touch the red lead of the multimeter to the left end of the grounding rod. Touch the black lead of the multimeter to the right end of the grounding rod. The resistance of the grounding rod is displayed on the multimeter screen in units of ohms.