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I was looking at my laptop's power supply and i noticed this symbol: enter image description here

To me totally looks like a "double isolation class 2" IEC 61140 combined with the IEC 60417 - 5018 symbol (Functional earthing; functional grounding), but does such thing exists in any standard? I couldn't find it in IEC 60417.

The negative output of the power supply is connected through a 10kohm resistance to the earth pin of the mains plug (or at least this is what i can measure from the ouside).

  • Isn't this breaing the double isolation condition?
  • Is the earthing there only for reference?
    If that's the case, why bother with the 10k resistor?
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  • \$\begingroup\$ It means Functional earthing; functional grounding (US) The term "functional earth" as used in the standard is only for cases where a special terminal is provided for the user or installer to connect to an external earth, usually for the purpose of noise reduction. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 10 '18 at 11:07
  • \$\begingroup\$ @TonyStewartolderthandirt This is not the case, no special terminal is used or available \$\endgroup\$ – valerio_new May 10 '18 at 11:23
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enter image description here

This Class 2 is the symbol for Double Insulation with no earth wire.

enter image description here

IEC 60417 Class-II-equipment-with-functional-earthing;-Class-II-equipment-with-functional-grounding-(US) Reference No : 6092 Registration date : 2013-03-30 Status : Active

Referenced in :

IEC 60065    
IEC 60950-1    
IEC 62368-1    
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  • \$\begingroup\$ Indeed! Hence my question... \$\endgroup\$ – valerio_new May 10 '18 at 11:22
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    \$\begingroup\$ Does your charger have a ground wire for line filter and double insulation and Maybe the leakage R is a faulty unit. Can you measure current Earth ground to DC 0V \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 10 '18 at 11:25
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    \$\begingroup\$ It is definitely not faulty, multiple units have this behaviour. And i can add another thing: laptop chargers without the earth pin on laptops that have a metal chassis often feel "stingy" to the touch, because there's some voltage difference from the isolated output's ground and you that are mains earthed. So that's why that system is there. But i want to understand the symbol usage and the related standards \$\endgroup\$ – valerio_new May 10 '18 at 11:39

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