I can attest to John's recommedations. Many years ago I worked in a company which had as an aftermarket product a vinyl cutting division. Machines which took large reels of vinyl, ran off specific lengths at high speed to spools which were shipped off to customers.
The speeds were up in the 50 or so feet per second level. The side of this fast moving vinyl could easily slice one's hand off if your hand happened to be in the wrong place at the wrong time. The vinyl was run through several rollers to maintain the proper tension and holes were cut along the sides. Amazingly high ESD levels were generated. The machines were drawn to my attention when one of the workers had to go to the emergency room. According to him, a spark about 18 inches long hit him when he was changing spools. I measured the distance later and he wasn't that far off. IIRC, research provided three ways to reduce the charge: one with tinsil or strapping of some sort, one with a slight radioactive charge generation device, and one with a +/- charge generator much like what's used in an air deionizer. We chose the tinsil and it worked great. BUT, they had to be changed on a regular basis. As far as designing for ESD in ungrounded products, I think you'll be forced to make provisions somehow with say braiding to ground anyway. One of the requirements in 1950 is to ground any exposed metal parts accessible to the end user. Not sure if this applies to your product, but something to that I think should be considered. If you're using a plastic housing with conductive coating, that coating won't be enough since it's not a reliable for grounding and is not accepted as a means of grounding by safety. - Doug McKean ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
