ANSI/ESD S20.20 covers items susceptible to damage by electrostatic discharges greater than or equal to 100 volts Human Body Model (HBM). Wireless wrist straps do not reliably remove charges to less than 500 volts. Here's information from a company selling wireless wrist straps: "In effect, the wireless wrist strap slowly neutralizes static electricity on a human body and maintains the potential of a human body below 500V, which is a great improvement from 3 to 5 kV measured without the wrist strap. The wireless wrist strap is not intended to replace conventional wrist straps. However, a wireless wrist strap, supplied with an additional coil cord for direct grounding, not only replaces conventional wrist straps, but provides additional protection when a person using it has to move away from the hard wired grounding point, (which is often a case in the electronics assembly, kiting, stock room, inspection, service or development working environments). Source: http://www.bomir.com/online/zerocharge/ground/wireless.htm Practical Points, Benefits and Precautions: * Please, do not touch electronics components immediately after installing the wireless wrist strap on your wrist. Allow minimum 60 seconds for the wrist strap to neutralize high levels of static electricity already existing on your body. * Do not use wireless wrist straps as your primary grounding device (unless it is a 2 in 1, Model AML-301A and is used with the grounding cord)." Source: www.bomir.com/online/zerocharge/ground/wireless.htm See http://www.esdjournal.com/techpapr/sfowler/wireless.htm Evaluation of Wireless Wrist Straps by: ESD Journal Lab We have been asked many times over the past few years about the viability of wireless wrist straps. The following is our evaluation of one wireless wrist strap. We used a wireless wrist strap that is advertises : "It operates using a combination of several physics phenomena like "Ion Neutralization, Skin Effect, Point Discharge and Corona Discharge Effect" combined with the principle of differential potential to collect and dissipate static electricity. It is a combination of bio-industrial and electronic technologies. In effect, the wireless wrist strap neutralizes over 80% of the static electricity on a human body and maintains the potential of a human body below 150V which is low enough to protect electronic components." The following is a summary of our evaluation of the strap: The wrist strap came with a conventional cord for use at the workbench. However, it is claimed to neutralize the static on a person without the cord attached "after 15 seconds." * Our tests showed that the wrist strap when connected by it cord had a resistance from the wearer's hand to ground of 1.3 MegOhms. * Our technician wore insulative shoes (> 10,000 MegOhms) and walked on an insulative floor. * We charged the technician to 2,000 volts. * When and he walked around with the uncorded wrist strap on, we saw a decay of the static charge to about 1,000 Volts in 90 seconds. * When and he walked around without the wrist strap, we saw a decay of the static charge to about 1,000 Volts in 90 seconds. * There was no difference in the time to decay to 1,000 with or without the wrist strap in place. * With the wrist strap on the walking technician, his potential never went below 700 volts for over 3 minutes. We dissected the wrist strap to see what inside would account for the claimed neutralization. We found only a 1 MegOhm resistor. This supports our findings that the wireless wrist strap no method for neutralizing a person not connected to ground by a conventional cord. It is our opinion that no currently available methods or devices exist which will effectively ground a person without a tethered cord to ground or at least a large capacitance. Sorry! Something that sounds too good to be true probably is. --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------