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Electrode Placement for Testing Resistive Surface (Source: ESDA)

There are several ESD floor test methods associated with and recommended by voluntary associations with a keen focus on the phenomenon and control of static electricity in work environments. Many of the test methods (ANSI/ESD STM7.1 and ASTM F150) are developed to report the characterization of ESD floor materials and, more importantly, their performance in combination with a person wearing intended ESD footwear. ESD flooring manufacturers develop flooring material that can be characterized as electrically reactive. To characterize a material as an ESD floor, a megohmmeter test device intended for electrical resistance measurement is used by placing two electrodes on the test flooring surface three feet apart and applying a known voltage across the surface of the electrically reactive floor material. The resistance within the material is recorded by the megohmmeter device and must fall within clearly defined ranges. A floor with a surface resistance of < 1.0 x 106 is characterized as a conductive floor. A floor with a surface resistance of >1.0 x 106 and < 1.0 x 109 is characterized as a static dissipative floor.
The above characterizations do not clearly reflect resistance of the circuit where static charge on a person, connected to the floor with intended ESD footwear, and ESD floor travel to ground.

Digital (Right) and Analog (Left) Megohmmeters and Electrodes

Performance resistance test methods are performed using a megohmmeter with a hand-held probe and an electrode that is applied to ground. The known test voltage travels through the person, intended ESD footwear, the ESD floor and to ground. The resistance is recorded on the megohmmeter. The same resistance parameters for conductive and static dissipative resistance is now considered the performance in working combination.

Set Up for ANSI/ESD STM 97.1 Test Method (Source: ESDA)

The most important performance test method is the measurement of voltage generation (ANSI/ESD STM97.2) in combination with a person, intended ESD footwear, and an ESD floor. This test is performed using a static charge plate recorder and repeatable analyzing software for voltage generation. The test will indicate how much voltage is generated while standing, walking and working on an ESD floor while wearing intended ESD footwear. An additional observation can record the time it takes to dissipate to ground.
Digital Charge Plate Monitor

Digital Charge Plate Monitor

Electrically reactive and resistive materials used in designing an ESD floor material will have a varying result in generation of static voltage while wearing intended ESD footwear. Therefore simple resistance measurements across a surface will not indicate the performance of an ESD floor as it is intended to be used.

Set Up for ANSI/ESD STM97.2 Test Method (Source: ESDA)

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Jeff Faulkner
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