Conformity Magazine- May 2008 - (Page 23) ESD Open Forum ground has to be the same as for wrist straps, generally <35 megohms (<3.5 x 107 ohms). However, be careful with this because it is often difficult to get the same or lower resistance value through the floor and footwear system. ANSI/ESD S20.20 (and IEC61340-5-1) allows static dissipative floors as long as the resistance to ground from anywhere on the floor is less than 1 x 109 ohms, and personnel do not generate greater than 100 volts using the ANSI/ESD S97.2 test method (Floor Materials and Footwear – Voltage Measurement in Combination with a Person). A footwear system, or shoe straps along with the ESD control floor, provides a very good back-up system in the event that people forget to put on the wrist strap right away at their work station, and for people that walk by or deliver materials. There are other considerations as well, including cost, maintenance and durability. If you do your homework and assure proper installation and care, an ESD floor will provide you with added flexibility within your ESD protected area. About the Author Craig Zander of Restronics Company Inc. is the Marketing & Communications Business Unit Manager responsible for Threshold (the ESDA’s newsletter), the ESDA’s website, and marketing activities of the Association. Craig has been active in Standards Committees for many years. About the ESD Association Founded in 1982, the ESD Association is a not for profit, professional organization directed by volunteers dedicated to furthering the technology and understanding of electrostatic discharge. The Association sponsors educational programs, develops ESD Standards, holds an annual technical symposium, and fosters the exchange of technical information among its members and others. Additional information may be obtained by contacting the ESD Association, 7900 Turin Rd., Bldg. 3 Rome, NY 13440-2069 USA, Phone 315-339-6937, Fax 315-339-6793. Email info@esda.org. Website: www.esda.org. © Frenta | Dreamstime.com All of the major ESD Program Standards (JESD 625A, IEC61340-5-1 and ANSI/ESD S20.20) say the same thing about floors and floor mat type applications. These are considered optional. A wrist strap grounding system is considered the main type of grounding system for personnel, but a floor and footwear system can be used if the resistance to ground for personnel is the same as for wrist straps. However, if personnel are sitting down to do their work, a wrist strap type system must be used. If the base floor has resistance to ground values that are acceptable for your program, then you may use that for grounding of personnel through ESD-rated shoes or shoe grounding straps for all standing or mobile applications. Again, for the floor and footwear system to be considered the primary grounding system for personnel, the resistance to ground from their hand through their feet to the floor to Q: A: Some international standards note the ESD floor mat is optional. Is this accurate? mAy 2008 Conformity 23 http://Dreamstime.com http://www.esda.org
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