ESD Smock Testing Procedure requires the fabric to be measured as an "electrostatic dissipation" material on the Ohms Scale and grounded (electrically bonded to the grounding system) so that it is not a conductor. floating isolation. In this article, we take a look at how ANSI/ESD S20.20-2014 defines an electrostatic jacket (ESD jacket) and explains the "isolated floating conductor" problem when wearing pants. ESD shirt.

According to ANSI/ESD S20.20, ESD clothing is “Static Control Garment”, or “Groundable Static Control Garment” or Groundable Static Control Garment System.

1. ESD Smock Requirements for ANSI / ESD S20.20

The minimum definition of an ESD jacket is that it is capable of dissipating static electricity. This means that the sleeve resistance is measured panel-to-panel with a surface resistance of less than 1 x 10 ¹¹ ohms.

“Static Control Garment” is understood as a garment (clothing) with a surface resistance < 1 x 10 ¹¹ ohms when measured from point to point (point to point) on the garment. T-shirt.

To perform this test, the garment shall be electrically isolated (placed on an insulating surface). Then place the electrodes connected to the meter on the sleeve plates of the garment.

The meter will measure the path of lowest resistance between electrodes placed on the sleeves.

This is also sometimes referred to as the "panel-to-panel conductivity" test. The reason is that it measures impedance through all the panels of the garment: sleeves, bodice, etc.

“Groundable Static Control Garment” has a surface resistance <1 x 10 ⁹ ohms measured at the grounding point (electrode 1 placed on the sleeve, electrode 2 on instead of grounding point).

To perform this test, you will replace one of the electrodes on one of the sleeves with ground.

The requirement for the resistance to be less than 1 x 10 ⁹ ohms (1 gigohm) is important in that it correlates with the ANSI/ESD S4.1 recommendation for workstation mats and the TR53 recommendation for shoe insoles.

“Groundable Static Control Garment System” has a surface resistance <3.5 x 10 ⁷ ohms measured at the point of grounding it to the wearer when connected by a strap wrist.

In ANSI/ESD S20.20-2014, this was covered under “8.2 Personnel Grounding” in Note 2 from Table 2: “For situations where ESD clothing is used as part of the grounding line of the wristband, the total system resistance including person, clothing and ground wire should be less than 3.5 x 10 ⁷ ohms - For situations where an ESD garment is used as part of the wrist strap grounding path, the total system resistance including the person, garment, and grounding cord shall be less than 3.5 x 10 ⁷ ohms”

This makes sense in that it correlates with TR53's recommendation that the wristband have a resistance of <3.5 x 10 ⁷ ohms.

2. Isolated Floating Conductors

ESD vests are exactly "groundable" because they're woven with conductive black carbon fiber.

If an ESD Garment (ESD Garment) is not electrically bonded to a grounded carpet, wristband or floor, it becomes essentially a floating lightning rod – a “floating conductor” ly - isolated floating conductor". The ESD Association acknowledged the problem of floating conductors in TR20.20-2008 section 5.3.13 'Garments - Garments':

"After verifying that the garment is capable of conducting electricity through all panels, the garment must be electrically bonded to the wearer's grounding system so as not to act as a floating conductor."

“The most important concept in the field of electrostatic control is grounding. Mounting all conductors and dissipations in the workplace to ground allows the accumulated charges to equalize with the earth potential. A grounded conductor cannot hold a static charge - The single most important concept in the field of static control is grounding. Attaching all electrically conductive and dissipative items in the workplace to ground allows built-up electrostatic charges to equalize with ground potential. A grounded conductor cannot hold a static charge”. – Quoting Part 3: Basic ESD Control Procedures and Materials