ESD Systems - Questions And Answers

1) Is there a standard distance to measure the floor resistance, and how many points should we take for measurements? 2) The trolleys that we used to keep parts and components are painted. All our components are inside the original packaging i.e.: tape and reel, tube or tray. Can these components be damaged due to ESD when removed from the trolleys? The trolleys wheels are insulative and used a drag chain to ground. - Anonymous, Palau, Malaysia

1) Yes, a three foot separation between electrodes is advised when using a megohmeter with 100 volts across the probes per the ESD Association’s standard ESD S7.1-1994 when doing point to point measurements. There is a specific pattern of probe placement to follow as depicted in the standard. It is highly recommended to measure and existing floor’s resistance to ground instead of point to point. Point to point is good for characterizing a floor material, but resistance to ground is good for determining the functionality of the ESD floor. For a resistance to ground measurement, a minimum of 5 tests per contiguous floor material or per 5,000 square feet is recommended. 2) Assuming that the carts are metal and painted with ESD paint, the only concern would be the handling of the components by an un-grounded (charged) operator, as not all packaging mentioned is known to be ESD safe. Especially if the operator is removing components from the manufactures packaging. These packages, if ESD dissipative, should be place on a grounded dissipative work mat before opening them.

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