ESD Systems - Questions And Answers

Well meaning though it may be, many electronics manufacturers assume that an "electrical ground" (i.e. mat or strap grounding to an electrical drop box, etc.) is a suitable ground. I have been trained that this is NOT a suitable ground and that a sufficiently long grounding rod driven into the earth is the only "proper" ground for ESD. Why is this? - Anonymous, Boulder, CO

Good question. Quick answer, yes, the electrical outlet box ground is a suitable ground for the ESD Safe Workstation. The ESD Association's standard on grounding, ANSI/EOS/ESD S6.1, defines GROUND to be a conducting connection, whether intentional or accidental between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of earth the position of portion of an electrical circuit at zero potential with respect to the earth a conducting body, such as the earth or the hull of a steel ship used as a return path for electric currents and as an arbitrary zero reference point. Also, an ESD GROUND is defined as the point, electrodes, bus bar, metal strips, or other system of conductors that form a path from a statically charged person or object to ground. The electrical outlet at any workstation, if wired properly (check with a local electrician), will have a ground path (conductor). This ground path connects to the ground at the power distribution panel for the building, which has a direct connection to a ground rod that is driven into the earth according to the ANSI/NFPA 70 (National Electrical Code) and the ANSI/IEEE STD 142 (IEEE Green Book). Especially when and ESD Safe Workstation has power equipment, the ESD Ground should be the same as the power ground. The power ground can easily be found at any duplex outlet (or other properly wired electrical outlet), and direct connection to ground can be obtained by connecting the Common Point Ground of the ESD Safe Workstation to the electrical outlet (via the ring terminal of the ground cord in direct contact with the outlet plate screw or ground screw). The fact that you would use a ground rod at each individual workstation can cause problems, as the ground reference between neighboring ground rods can have a potential difference caused by a ground loop or other naturally occurring electrical currents between the ground rods. This includes the potential difference between equipment ground and the ESD Ground, if a separate ground rod is used. The difference in potential between differing ground systems can cause ESD Events, since there is a potential difference between them. NOTE: The "Electrical Ground" or "Bonding point" is preferred over a separate ground.

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