Hi All and John! Back to basics (as I read them) and a light hearted review of published information.
ICNIRP and a few other sources put the threshold of perception as 1mA a.c. Other sources give the resistance of a person as 2kOhms. This puts the voltage associated with the perception of an electric shock at 2V a.c. Death can occur (according to some documents) with a.c. current above 9mA - that would be 18Va.c. for a 2kOhm person Taking a step further, the resistance of a person that has lost the normal layers of skin is very low - so a 2V a.c. source connected to two cheese graters could be lethal! Of course 2V a.c. has never been safe if the current is unlimited - it might not shock you, but it can give you a shock to find that the low voltage source has caused a fire. 1.4V d.c (a NiCad cell) put a good burn on the inside right of my right thigh when I mistakenly put the car keys in the same pocket as the spare re-chargables for my camera. That gave me a shock! Many years ago, I remember being told that an old lady died from a shock caused by a 9v "radio" battery - but I cannot vouch for the truth of this tale. Seriously, there is a risk with electricity that never quite goes away. The lower the voltage, the greater is the chance that a person will survive the shock. Given the range of resistance that exists in people, it would be a very bad day if someone with 2k resistance came into contact with 18V and died as a result. However, if you want to have a safe product, it is probably not worth arguing over what voltage is safe, it is better to prevent access to any voltage - just in case the person has been grating cheese. There are some serious thoughts in the above if you look for them. Have a good week end Regards Tim ************************ SELEX Sensors and Airborne Systems Limited Registered Office: Sigma House, Christopher Martin Road, Basildon, Essex SS14 3EL A company registered in England & Wales. Company no. 02426132 ******************************************************************** This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. ******************************************************************** - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@socal.rr.com> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
