The ANSI / ESD Association standard used in the United States to test that an ESD Mat is “static dissipative” is ANSI / ESD S4.1. “Worksurfaces – Resistance Measurements“.
This requires the use of a Surface Resistivity (ESD) Meter to perform both resistance-top-to-top (RTT) and resistance-to-groundable point (RTG) tests.
• RTT Testing for ESD Resistance per ANSI / ESD S4.1
• RTG Testing for ESD Resistance per ANSI / ESD S4.1
1. Surface Resistivity vs. Surface Resistance
“The degree of protection afforded by a worksurface is strongly related to the time needed to discharge an object…. [R]esistance seems the best single predictor of performance of ESD-protective worksurfaces.”
– ANSI / ESD S4.1-2006
Resistivity and Resistance are not technically the same thing. Resistivity is measured in ohms / square. Resistance is measured in just ohms.
Theoretically, surface resistivity is ten times greater than resistance. For example, a material that measures 108 ohms in surface resistance should measure 109
For testing purposes, per ESD TR20.20, the correct unit of measurement is surface resistance (just ohms).
A material is considered static dissipative if it has a resistance greater than 1 x 106
2. Measure Resistance Top to Top (Point to Point) (RTT)
ANSI / ESD S4.1 guidelines (section 8.0) state that point-to-point (RTT) tests should find the mat has greater than or equal to 1 x 106 ohms of surface resistance.
Test Procedure in accordance with ANSI/ESD S4.1 section 6.4 Periodic Worksurface Testing:
• Do not
• ESD Sensitive devices shall also be removed.
• Use two 5 pound electrodes and place them on the most commonly used area of the surface. Ensure that the electrodes are about 10″ apart from each other and 2″ away from any edge and 3″ away from any grounded point.
• Push and hold the Test Button until the surface resistance reading is displayed.
• If the most used area is not obvious, use two points near the center of the surface.
3. Measure Resistance to Groundable Point (RTG)
ANSI / ESD S4.1 guidelines (section 8.0) states that resistance-to-groundable point (RTG) tests should find the mat has between 1 x 106 and 1 x 109 ohms of surface resistance.
Test Procedure in accordance with ANSI/ESD S4.1 section 6.4 Periodic Worksurface Testing:
• Do not
• ESD Sensitive devices shall also be removed.
• Clip the black test lead to a grounded point.
• Use one 5 pound electrode on the other test lead and place the electrode on the furthest convenient point on the surface.
• Push and hold the Test Button until the surface resistance reading is displayed.