Re: Re: Electric Shock and Water
If your colleage doesn't understand why you shouldn't mix water and electricity in general, just tell him that water has a tendency to be rather unpredictable and can go anywhere. Someone likened it to a three dimensional resistor and that's an excellent example. Add to it a very deformable 3D resistor. And since electricity likes to follow water, electricity will also end up going anywhere. Other than that, I agree it's a pretty naive question. I picture the guy in bare feet on the metal ladder in water with drill in hand asking, so what's the matter? - Doug McKean --- 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: 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.
Re: Electric Shock and Water
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.
Re: Electric Shock and Water
No risk of electric shock at these voltages. But in salt water environments, a greatly increased risk of corrosion. Which could in turn lead to a shock or fire hazard. Slightly off topic, but a valid point to be considered. Peter Merguerian wrote: Jason, Please explain to your colleague that for North American requirements (as depicted in the NEC and CEC) there is no risk of electric shock or fire from circuits in wet locations for up to 21.2 V. For higher voltages you should start taking steps to minimize the risk of water ingress and the risk of a person coming in touch with the circuits. In Europe, I believe the voltage level is somehat lower; if I recall correctly, 15 V. Someone correct me if I am wrong! This e-mail message may contain privileged or confidential information. If you are not the intended recipient, you may not disclose, use, disseminate, distribute, copy or rely upon this message or attachment in any way. If you received this e-mail message in error, please return by forwarding the message and its attachments to the sender. PETER S. MERGUERIAN Technical Director I.T.L. (Product Testing) Ltd. 26 Hacharoshet St., POB 211 Or Yehuda 60251, Israel Tel: + 972-(0)3-5339022 Fax: + 972-(0)3-5339019 Mobile: + 972-(0)54-838175 -Original Message- From: jasonxmall...@netscape.net [mailto:jasonxmall...@netscape.net] Sent: Thursday, January 03, 2002 12:57 AM To: emc-p...@majordomo.ieee.org Subject: 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. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list.
Re: Electric Shock and Water
If you work at a site with a large air conditioning plant or a chilled water system, then chances are your facilities manager will have a conductivity cell. They are used as a very quick means to monitor water purity and to check for signs of corrosion. Units are expressed in uS/cm and technically pure water is non conductive. In reality all water will contain conductive ions as soon as it is exposed to CO2 in the atmosphere. The higher the impurity of the water, the more ions available and the higher the conductivity. Typical example values would be, Ultra Pure water 1 uS/cm De Ionized Water 10uS/cm Drinking water 500-1200uS/cm Salt Water 5000-10,000uS/cm Water temperature is also plays a big factor, higher temp, again more ions, to higher conductivity. John Woodgate wrote: I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in 200201030028.qaa08...@epgc264.sdd.hp.com) about 'Electric Shock and Water', on Wed, 2 Jan 2002: 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. 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. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- 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. -- Andrew Carson - Product Safety Engineer, Xyratex, UK Phone: +44 (0)23 9249 6855 Fax: +44 (0)23 9249 6014 --- 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: Electric Shock and Water
Jason, Please explain to your colleague that for North American requirements (as depicted in the NEC and CEC) there is no risk of electric shock or fire from circuits in wet locations for up to 21.2 V. For higher voltages you should start taking steps to minimize the risk of water ingress and the risk of a person coming in touch with the circuits. In Europe, I believe the voltage level is somehat lower; if I recall correctly, 15 V. Someone correct me if I am wrong! This e-mail message may contain privileged or confidential information. If you are not the intended recipient, you may not disclose, use, disseminate, distribute, copy or rely upon this message or attachment in any way. If you received this e-mail message in error, please return by forwarding the message and its attachments to the sender. PETER S. MERGUERIAN Technical Director I.T.L. (Product Testing) Ltd. 26 Hacharoshet St., POB 211 Or Yehuda 60251, Israel Tel: + 972-(0)3-5339022 Fax: + 972-(0)3-5339019 Mobile: + 972-(0)54-838175 -Original Message- From: jasonxmall...@netscape.net [mailto:jasonxmall...@netscape.net] Sent: Thursday, January 03, 2002 12:57 AM To: emc-p...@majordomo.ieee.org Subject: 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. --- 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 Heald
Re: Electric Shock and Water
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in 200201030028.qaa08...@epgc264.sdd.hp.com) about 'Electric Shock and Water', on Wed, 2 Jan 2002: 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. 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. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- 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: Electric Shock and Water
I read in !emc-pstc that jasonxmall...@netscape.net wrote (in 738426ed.4080ead3.73ea6...@netscape.net) about 'Electric Shock and Water', on Wed, 2 Jan 2002: 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. I think this lacks clarity. I suggest that you explain that you don't get a shock in the first case because your footwear is non-conducting. But if your feet are wet, there is a conducting path from them to ground AND you don't even have the limited protection afforded by the resistance of dry skin. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. --- 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: Electric Shock and Water
Water, as is generally conductive, forms a better surface contact ( to you), reducing the surface resistivity (yours), thus allowing a greater flow of lethal current through the body (yours) from an energised electrical device. And when coupled with any, or all of the previous faults, you may kiss it good-by, or expect to spend a long vacation in the burn unit of your local hospital. John Shinn, P.E. -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of jasonxmall...@netscape.net Sent: Wednesday, January 02, 2002 2:57 PM To: emc-p...@majordomo.ieee.org Subject: 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. --- 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: Electric Shock and Water
Hi Jason: Water comprises a 3-dimensional resistor. The value of the resistor depends on: * the purity of the water itself (the resistance is inversely proportional to the purity); * the dimensions of the electrodes (i.e., the conductors in contact with the water); * the distance between the two electrodes; * the cross-sectional dimensions of the current pathway; * other conductors in the water (which may short out some of the water, or may carry some of the current to another load). The hazard of water is that it displaces air insulation in typical electrical products. Most products rely on air insulation for both performance and protection against electric shock (which is why safety standards include minimum dimensions for clearance). If water displaces the air insulation, then an unintended current path is created. If the body happens to touch that water, then the unintended current path may include the body. If your colleague understands that air is commonly employed as an electrical insulator (e.g., overhead power lines), then I would hope that he could understand that water displaces the air, and thereby provides an unintended (and uncontrolled) conductive path. (Most of your examples are examples of water displacing air insulation.) Water on the skin tends to enlarge the electrical connection to the body. The larger the area of electrical connection to the body, the more susceptible the body is to the same value of current. (This explains your leakage paragraph.) Best regards, Rich ps: Is there a value (or range of values) for the resistance of water? Is there a standard way of measuring the resistance of water? --- 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.
