Ground Impedance Measurement

Target Intelliground™ Reading: Less than 1 ohm. (This is the recommended maximum value set forth by the Institute of Electrical and Electronics Engineers (IEEE) Standard 1100-2005 (Emerald Book))

Likely Cause For High Impedance Reading: Loose connection at the tested outlet OR along Ground path from 120VAC outlets upstream from the point of test!
(Be sure to test ALL outlets!)

Likely Solution: Engage a qualified electrician to tighten up the ground connections at the suspected outlet(s).

Why Is Ground Impedance Important?
A circuit as simple as a 120VAC outlet can affect so many things within the electrical environment, regardless of whether it’s a complex data center or a small room in a home. High Equipment Grounding Impedance essentially restricts the passage of current that is so essential when trying to mitigate safety, fire, or equipment performance issues under the following conditions:

  1. Electrical Ground Fault
  2. Lightning.
  3. Electromagnetic Interference.
  4. Radio Frequency Interference.
  5. Electric Utility Voltage Quality Issues

It is also recognized that the electromagnetic compatibility of an entire equipment room is compromised if the impedance of its conductors is too high; particularly the equipment grounding conductor.

It is important to note that the physical wiring of the equipment grounding conductor path is crucial for mitigation since deficiencies can increase the impedance greatly, depending if the disturbance is high frequency (HF) or low frequency (LF). Physical items to consider are listed below in order of importance:

    • Tightness of connections.
    • Length of conductor.
    • Number of bends in conductor path.
    • Bend radius in conductor path.


Ground Impedance Measurement