RE: Re: Electric Shock and Water
Rich Do you use Google.com for searches. I did a search on water conductivity yesterday and got a lot of hits with typical values. Many related to biological studies. See, for example http://www.dartmouth.edu/~bio59/conductivity.htm -Jason Rich Nute ri...@sdd.hp.com wrote: Hi John: Is there a value (or range of values) for the resistance of water? The data exists; it depends, of course, on solute nature and concentration. Try a web search. I did a web search before my post. There is lots of data on the use of water resistance and water conductivity, but I found nothing on the values of water resistance or water conductivity. Somewhere in yesterday's web search, I recall having seen a reference to DI water has being 18 megohms maximum, and ordinary water being in the neighborhood of 2 kilohms. But, neither of these values was well-documented, and questionable as to applicability to the question at hand, so I did not quote them. I did another search today. Water conductivity measurements are used to estimate the total dissolved salts (TDS) in the water. This site explains TDS and gives conductivity values for various lakes: http://wow.nrri.umn.edu/wow/under/parameters/conductivity.html (The last two paragraphs of this URL are recommended reading.) This URL has lake and ocean water ranging from 100,000 ohms to 23 ohms and even 6 ohms. I found a water conductivity meter that measures up to 1999 milliSiemens. This would correspond to 0.5 ohm. This would imply the resistance of water would range from infinite to something on the order of 50 ohms (assuming the meter range would exceed the expected values by 100X). Perhaps this meter is a conductivity cell, but the specs do not describe it as such. http://www.sentry-products.co.uk/Products/Water%20Conductivity%20Meters$20Body.htm I find it disturbing that the web does not have more published values for water conductivity. I wonder if this is because there are no standard values for water resistance? I suspect that the values are completely variable and unpredictable. I would think that water supply authorities would publish EC and TDS of the water supplied to customers as these are measures of water hardness. Is there a standard way of measuring the resistance of water? Yes; a conductivity cell. An apparently simple device that isn't. Once again, a web search will probably disclose more than you ever wanted to know. Using your suggestion, I did a search and found limited (not more than I ever wanted to know) information on the conductivity cell: http://www.ussl.ars.usda.gov/answers/mc0.htm http://www.thermo.com/eThermo/CDA/Products/Product_Listing/0,1086,107687-161-161,00.html The first URL explains the theory of operation in general terms. The second URL is a manufacturer of conductivity cells. Best regards, Rich --- 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 Healddavehe...@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: No longer online until our new server is brought online and the old messages are imported into the new server. -- __ Your favorite stores, helpful shopping tools and great gift ideas. Experience the convenience of buying online with Shop@Netscape! http://shopnow.netscape.com/ Get your own FREE, personal Netscape Mail account today at http://webmail.netscape.com/ --- 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 Healddavehe...@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: No longer online until our new server is brought online and the old messages are imported into the new server.
Electric Shock and Water
My apologies if this is just too naive... I am trying to explain to a collegue why there are so many cautions against mixing water with electricity. He is not the type to accept common sense as an answer. This is what I have reasoned so far... MAL-OPERATION Water is generally conductive. If it enters the area of a chassis that houses control elements such as relays or switches, it can short circuit the control elements and cause the affected device to operate unexpectedly, and sometimes in unexpected ways. ENERGIZING SURFACES Water is generally conductive. If it enters a chassis containing hazardous voltages it is possible it may act as a conductor of the voltage to an otherwise un-energized conductive surface. If the conductive surface, for whatever reason, is itself not sufficiently grounded, it can carry hazardous voltage potentials. INCREASED LEAKAGE CURRENTS Water is generally conductive. If you are working on a chassis and accidentally touch an energized contact, you may not experience any shock because there is no current path between you and the voltage source supplying the contact. Let us assume the contact is energized by a local AC mains. There is always SOME leakage current possible from where you are standing back to a grounded point. Usually it is a very small leakage. However, if you are standing in water, the leakage current is likely to be much higher, and you may experience a serious electric shock from your accidental touching of a contact. AVALANCHE EFFECT Water is generally conductive. If it enters a chassis with high power electrical components, it can instigate an avalanche of failure that results in the release of a lot of energy. For example, the water can provide a short circuit between two potentials. As it carries current, the water may heat up quite rapidly, in doing so it creates steam. The effects of the heat and steam may then provide an even lower resistance path for additional current flow...and so an avalanche of conductivity (from less conductive to more conductive) is started... I welcome any comments and additional generic scenarios. Regards, Jason Mallory Product Safety Consultant. -- __ Your favorite stores, helpful shopping tools and great gift ideas. Experience the convenience of buying online with Shop@Netscape! http://shopnow.netscape.com/ Get your own FREE, personal Netscape Mail account today at http://webmail.netscape.com/ --- 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 Healddavehe...@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: No longer online until our new server is brought online and the old messages are imported into the new server.
What changed with IEC 61010-1 revision?
Does anyone know of a resource for a summary of what was revised in IEC 61010-1 2nd Edition? I.E. what is the delta from the 1993 version? Will EN 61010-1 soon be revised to match IEC 61010-1 2nd Edition? Thanks Jason Mallory Product Safety Consultant. -- __ Your favorite stores, helpful shopping tools and great gift ideas. Experience the convenience of buying online with Shop@Netscape! http://shopnow.netscape.com/ Get your own FREE, personal Netscape Mail account today at http://webmail.netscape.com/ --- 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 Healddavehe...@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: No longer online until our new server is brought online and the old messages are imported into the new server. --- 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 Healddavehe...@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: No longer online until our new server is brought online and the old messages are imported into the new server.
RE: Re: Revised EMC standards and CE Declarations.
Two more questions Newgroup Lingo? In the following, IIRC means If I Recall Correctly The 'dow' for the old edition is given in the front of the new one and is 2001-07-01, IIRC. I can't check at this instant. So you needed to re- test before that date (1 July this year). -- Regards, John Woodgate, OOO - Own Opinions Only. Declaring to Essential Requirements = If I have been declaring to the essential requirements of the EMC Directive using a Competent Bodies test plan and oversight, does the revision of standards that may have been used in whole or in part require re-evaluation by the Competent Body? -Jason Mallory Product Safety Consultant -- __ Your favorite stores, helpful shopping tools and great gift ideas. Experience the convenience of buying online with Shop@Netscape! http://shopnow.netscape.com/ Get your own FREE, personal Netscape Mail account today at http://webmail.netscape.com/ --- 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 Healddavehe...@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: No longer online until our new server is brought online and the old messages are imported into the new server.
Revised EMC standards and CE Declarations.
Hi all. EN 50082-1:1992 was replaced by EN 50082-1:1997. According to the newapproach.org website, from 1/7/2001 the old version no longer allows one to presume conformity to the EMC Directive. Does this mean I need to retest all equipment to the new standard before I can declare conformance? My guess is YES. Thanks in advance for any confirmation or correction. -Jason Product Safety Consultant -- __ Your favorite stores, helpful shopping tools and great gift ideas. Experience the convenience of buying online with Shop@Netscape! http://shopnow.netscape.com/ Get your own FREE, personal Netscape Mail account today at http://webmail.netscape.com/ --- 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 Healddavehe...@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: No longer online until our new server is brought online and the old messages are imported into the new server.
