One reliable method of assessing the condition of terminal junctions in electrical systems is by measuring the junction resistance. The junction resistance should have a very low resistance to current to efficiently carry power to other components of the electrical system. If the junction has microscopic breaks, corrosion or other contaminants, the resistance may increase. This can result in localized Ohmic heating and result in eventual breakdown of the junction. These defects may not be visually obvious until they cause severe problems.
Normal Ohmmeters cannot measure extremely low resistance commonly found in terminal junctions. In order to measure resistance below 1Ω, an Ohmmeter with a Kelvin Double Bridge input is used. This configuration allows the tester to isolate the resistance of the leads and test probes which may affect the accuracy of the test results. Most of the meters used today areDLROs or Digital Low Resistance Ohmmeters. These devices are microprocessor based to ensure accurate measurements. A DLRO often has an output current ranging from 10 Amperes to several hundred Amperes.