ESD Systems - Questions And Answers

I wonder how effective and reliable is grounding through daisy chain system, (by this I mean having five workstation connected to ground by one common wire) instead individually connected to ground? - Julio, New Windsor, NY

Good question. Daisy chaining ESD mats together is generally not a good grounding practice, especially if they are truly daisy chained. If you have 5 workstation work surfaces truly daisy chained, then the resistance between the two snaps of each mat is added to the grounding resistance as it goes down the line, therefore the last mat will have the equivalent resistance of ground plus four times the resistance between two snaps in one mat (say 5x10⁷ ohms) which would yield an equivalent resistance of 2x10⁸ for the ground path on the last mat/work surface. If they are not truly daisy chained, but connected in parallel (each mat having its own direct connection to ground) then this is the proper setup for grounding. You might be able to do this non-traditionally with one wire, but for each work surface, there needs to be an electrical connection (snap) to the mat. This could be accomplished with a custom made wire with five 10 mm snap studs directly connected to it, spaced appropriately to connect to all 5 work surfaces. This would in essence be like connecting 5 individual ground wires, one to each mat, all tied to the same ground point or a parallel connection. What is important to remember in ESD control is to keep all conductors at the same potential. Grounding in parallel insures this, grounding in daisy chain fashion may compromise this goal.

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