In message <[email protected]>, dated Tue, 19 Jun 2007, "Kunde, Brian" <[email protected]> writes:
>We would like to come up with an internal test to ball-park measure >electromagnetic fields at line frequency (50/60Hz) to satisfy our >customers when such requests are made regarding compliance to the EU's >Physical Agents Directive (2004/40/EC). Any advice regarding test setup >and test equipment would be appreciated. > [snip] > >1. For IT and Laboratory equipment, what EMF test method standard >should we be looking at? Is there a harmonized test standard? For me, the problem is that there are too many standards that appear to include the power frequency range, without a clear indication of what applies and how. There is a Generic EN, which has not been offered by the CENELEC BT to the Commission for 'notifying' in the Official Journal because the Basic standard on which it depends for methods of measurement is not yet approved. It has been stated that ITE is known not to present an EMF hazard and need not be tested, but I know of no such official statement, even though IMHO it's true. Lab equipment covers a huge range, some products being designed to produce quite strong magnetic fields outside the box, so you would need to consider each product on its merits. > >2. What test equipment is required? A Google search popped up a lot >of hand held products that claim to measure EMF. Would such products do >what we need? It's very difficult to distinguish between the truly scientific ones and those offered to people who think they are 'electrosensitive'. The latter are often much too sensitive in terms of the ICNIRP exposure recommendations, so that the buyer actually gets a response even in very weak fields. In principle, you need an r.m.s. meter with a three-axis sensor and one that is calibrated in amps per metre, since that is how the ICNIRP values are given. The ICNIRP 'reference value' is about 8 A/m at power frequency. If the field strength is higher, you have to analyse the distribution in space to see if the Basic Restriction is met. This is a fair bit more difficult but can be done. Recent scientific papers have suggested that the ICNIRP values are lower than is justified, and indeed the IEEE values are higher. ICNIRP applied the 'precautionary principle' and it has been suggested that a 'safety factor' of around 50 was involved! This may be an exaggeration. But I have exposed my hands to 1000 A/m with no perceptible effect. > >3. Is this approach doable, or have I embarrassed myself by even >proposing such a test? Yes, it's doable, if insight is applied. References Guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz), International Commission on Non-Ionizing Radiation Protection (ICNIRP) BS EN 50392:2004 Generic standard to demonstrate the compliance of electronic and electrical apparatus with the basic restrictions related to human exposure to electromagnetic fields (0 Hz – 300GHz) IEC 62311 Ed.1: Assessment of electronic and electrical equipment related to human exposure restrictions for electromagnetic fields (0 Hz - 300 GHz) PD CLC/TR 50442:2005 Guidelines for product committees on the preparation of standards related to human exposure from [sic] electromagnetic fields -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
