ESD smock testing procedure

This reference article discusses ANSI/ESD S20.20-2014. For implementation, verify the applicable edition and garment test method; these historical extracts are not a complete certification procedure.

The three categories discussed are static-control garments, groundable static-control garments and groundable static-control garment systems.

1. ESD garment requirements

The original guidance describes a static-control garment with sleeve-to-sleeve or panel-to-panel resistance below 1 × 10¹¹ ohms.

Static-control garment

A static-control garment has point-to-point resistance below 1 × 10¹¹ ohms when measured between the specified points on the garment.

Place the garment on an electrically insulating surface. Connect the meter electrodes and position them on the garment’s sleeve panels.

The meter measures the resistance path between the electrodes on the sleeves.

This is also described as panel-to-panel testing because the measurement includes the connected garment panels, such as the sleeves and body.

Groundable static-control garment

A groundable static-control garment has resistance below 1 × 10⁹ ohms measured from a garment panel to its designated groundable point.

For this test, connect one meter lead to the garment’s designated groundable point instead of placing the second electrode on the other sleeve.

The original article discusses a resistance limit below 1 × 10⁹ ohms, or 1 gigohm, and relates it to the cited work-surface and footwear guidance. Apply the specific garment test method and acceptance limit for the relevant garment category.

Groundable static-control garment system

A groundable static-control garment system has total resistance below 3.5 × 10⁷ ohms through the person, garment and grounding connection when the garment is used as part of the personnel-grounding path.

The original article cites the personnel-grounding provisions of ANSI/ESD S20.20-2014: where a garment forms part of the wrist-strap grounding path, the total resistance of the person, garment and grounding cord must be below 3.5 × 10⁷ ohms.

The article relates this to the cited wrist-strap guidance, with resistance below 3.5 × 10⁷ ohms.

2. Isolated floating conductors

The illustrated ESD garment incorporates conductive carbon fibres that create a conductive network. Its grounding performance must be verified as a complete garment or system.

An ESD garment that is not electrically connected to an appropriate grounding system can act as an isolated conductor. The original article refers to this issue in the garments section of TR20.20-2008.

After confirming electrical continuity between garment panels, verify the intended connection to the wearer’s grounding system so that the garment does not act as a floating conductor.

Grounding is a fundamental ESD-control measure. Connecting suitable conductive and dissipative workplace items to ground allows accumulated charge to dissipate towards ground potential. Reference: Part 3, Basic ESD Control Procedures and Materials.