Grounding technique for EFT and Surge test

This paper provides grounding technique for immunity test like EFT and Surge which is most commonly required for any of the industrial or commercial product. The objective of this paper is to provide the practical and experimental grounding techniques to comply with immunity tests such as fast transients and fast burst in other terms which are called as low energy and high energy immunity test. The proper selection of grounding scheme depend upon specific application in use. For example a single-point grounding scheme operates better at low frequencies (signal frequencies below 300 kHz), and a multipoint ground behaves best at high frequencies (30MHz to 1GHz). Many system-level EMI problems can be avoided by paying careful attention to the grounding scheme used. Common-mode, common-ground impedance problems may be reduced by application of one or more of below techniques - a. Eliminate common impedance by using a single point ground. b. Separate and isolate grounds on the basis of signal type, level, and its frequency. c. Minimize ground impedance using ground bus, ground plane, or ground grid during PCB design. d. Use an inductor/capacitor in the ground connection to provide high-or low-frequency isolation. e. Reduce the common-mode ground loop currents by floating circuits or equipment; using optical isolators; or inserting common-mode filters, chokes, or isolation transformers.