The Smart Ground Multimeter, or SGM, is a state-of-the-art
computer based measuring system that performs the following
eight functions:
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SGM was developed by Dr. A.P. Sakis Meliopoulos of Georgia Tech under the sponsorship of the Electric Power Research Institute (EPRI). The data obtained by the meter is processed by the software which filters noise, removes harmonics and signal irregularities, and corrects voltage and transducer errors. The SGM auto-calibrates itself prior to each measurement. Data acquisition and storage are controlled by a portable computer (user furnished). The software warns the operator if signal levels are not within appropriate bounds. The SGM Story Until now, ground impedance measurements have been performed using variations of the fall-of-potential method. This method suffers from several well-known limiting factors: Measurements must be made on de-energized, isolated grounding systems, often impossible at existing sites and facilities. Ground potential rise measurements require the user to locate remote earth, i.e., to be outside the sphere of influence The necessarily long test leads create a likelihood for high interference levels. Low resistance grounds are particularly difficult to measure. Results have confidence levels that are unknown but typically low. The SGM overcomes these common disadvantages and offers the following improvements: The software has algorithms that compensate for and correct outside noise and interference allowing it to be used on energized systems. Measurements are based on ground potential differences at six different points. Relatively short leads are required. The grounding system impedance is measured. Confidence levels are calculated by the software. 
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