Getting Down to Earth 53APPENDIX IIIAttached Rod Technique (ART)Fall-of-potential testing is extremely reliable, highly accurate, conforms to IEEE 81 and gives the operator complete control over the set-up. Unfortunately, it is exceedingly time consuming and labor intensive, and requires that the individual ground electrodes be disconnected from the system. As described in Appendix II, the clamp-on testing is quick and easy, but has many limitations. It requires a good return path, is susceptible to noise, has reduced accuracies and cannot be used on isolated grounds. It is not applicable for installation checks or commissioning new sites and has no built in proof.The Attached Rod Technique (ART) method of testing provides some of the advantages of clamp-on testing (not having to disconnect the ground electrode) while remaining true to the theory and methodology of fall-of-potential testing. To understand the method, it is necessary to understand the theory and math behind it. In theory, a fall-of-potential measurement could be made without disconnecting the ground electrode if additional measurements were made with an earth leakage clamp meter (milliamp meter). Figures 25 and 26 show the three measurements that would be made.Fig 25: Ground resistance measurement
