Bob Brister asks why the limits for electric shock are 42.4 volts peak and 60 volts DC.
The limits for electric shock, 30 volts rms and 42.4 volts peak, come from the National Electrical Code. In particular, they come from Article 725, Tables 11(a) and 11(b) in the 1996 Code (Tables 725-31(a) and (b) in earlier Codes). They have been in the NEC for many, many years. Sorry, but I don't know the source for the NEC. The 60 volts DC limit came when telephone circuits were introduced into UL 1950 and IEC 950. This has already been discussed in this forum. One of the reasons for accepting 60 volts DC is that, according to the research, muscles do not tetanize when subjected to DC. This means that persons can always let go of a DC connection (i.e. they are not "frozen" to the connection). Best regards, Rich +===========================================================+ |Richard Nute |Quality Department | |Hewlett-Packard Company |Product Regulations Group | |San Diego Division (SDD) |Tel : 619 655 3329 | |16399 West Bernardo Drive |FAX : 619 655 4979 | |San Diego, California 92127 |e-mail: [email protected] | +===========================================================+
