For ESD purposes, materials are classified by their resistance to the movement of electricity. The following ranges and definitions are found in ESD Association or EIA standards publications:
Conductive materials: With a low electrical resistance, electrons flow easily across the surface or through the bulk of these materials. Charges go to ground or to another conductive object that the material contacts or comes close to. Conductive materials have a surface resistivity less than 1 x 10^5 Ω/sq or a volume resistivity less than 1 x 10^4 Ω-cm.
Dissipative materials: For these materials, the charges flow to ground more slowly and in a somewhat more controlled manner than with conductive materials. Dissipative materials have a surface resistivity equal to or greater than 1 x 105 Ω/sq but less than 1 x 10^12 Ω/sq or a volume resistivity equal to or greater than 1 x 10^4 Ω-cm but less than 1 x 10^11 Ω-cm.2
Insulative materials: Insulative materials prevent or limit the flow of electrons across their surface or through their volume. Insulative materials have a high electrical resistance and are difficult to ground. Static charges remain in place on these materials for a very long time. Insulative materials are defined as those having a surface resistivity of at least 1 x 1012 Ω/sq or a volume resistivity of at least 1 x 1011 Ω-cm.
How to Measure Surface Resistivity
The SRM200 Surface Resistance Meter is an easy to use tester for measuring surface resistivity. This SRM200 uses parallel electrodes and concentric rings to accurately measure RTT, RTG, or resistivity for periodic verification, factory audits or test lab evaluation of product.
This meter is designed to be used in all facets of material production including engineering, maintenance, quality control, incoming inspection, manufacturing, research, or sales departments for the testing of anti-static mats, floor finishes, paints, wrist straps, smocks, foot wear, bags and containers.
The SRM200 meets periodic test requirements per Compliance Verification ESD TR53 and conforms to ANSI/EOS/ESD (S4.1, S7.1, S12.1, S2.1).