ESD Systems - Questions And Answers

Can you tell me why a wrist strap has to touch skin? I was thinking I could wear on top of my shirt, which is 100% cotton. I looked at the S.20.20 and it gave me really nothing.

The path-to-ground is the person’s sweat layer and the conductive portions of the Wrist Band.

Cotton and most clothing is insulative; one would not want to put an insulative layer between the person’s skin and the conductive portion of the Wrist Band. It would likely thwart the purpose of the Wrist Strap removing ElectroStatic charges from the person.

The ESD Association Wrist Strap standard is ESD S1.1; it includes: “Visually examine the wrist strap cuff to ensure that it is adjusted snugly to the skin”. [ESD S1.1 section 6.1.6 A Trouble Shooting]

“the ‘failing’ person’s skin may have a high electrical resistance. The use of an expandable metal-cuff and/or dissipative lotion or gel may reduce the person’s skin contact resistance.” [ESD S1.1 section 6.1.6 C: Skin Contact Resistance]

See ANSI/ESD S20.20 Table 1. The recommended technical requirement range for Wrist Strap System is less than 35 x 10^6 ohms.

Wrist Strap “An assembled device consisting of a wrist cuff and ground cord that provides electrical connection of a person’s skin to ground.” [ESD S1.1 section 3. Definition of Terms]

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