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I have seen the different answer posted in internet.

Many people are saying glow of neon light on tester is due to stray capacitor formed by our body and ground. I am ok with that until I found out tester also works on DC. So I get confused there, if it is DC then i think the capacitor will not work but tester glows in both poles. So please help me understand here. If it is due to stray capacitor then how it works in DC?


TYPICAL "NEON TESTER":

Tested voltage is contacted with blade tip.
Finger is placed on metallic top cap.
Circuit is Voltage_in - tip_resistor - neon - YOU.
Neon lights if voltage present.

enter image description here

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  • \$\begingroup\$ Have you SEEN it work with DC yourself? What voltage DC? High voltage DC will work if there is enough ground leakage from person to ground. \$\endgroup\$
    – Russell McMahon
    Jul 6, 2015 at 2:53
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    \$\begingroup\$ This question had THREE votes to close solely because it looked bad - even though it is an excellent question. You MUST start sentences with a capital letter!!! - if you do not, people will treat you badly. That's life. | You MUST capitalise "I" when I = you. Do not use text speak abbreviations such as "plz". Use whole wrds nd du nt abbrviate :-) - If you follow the above "rules" people may be able to see past the language to the excellent technical questions and answer them properly. \$\endgroup\$
    – Russell McMahon
    Jul 6, 2015 at 2:59

1 Answer 1

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An excellent question.

High voltage DC will work if there is enough ground leakage from person to ground.
If the resistance to ground is about 1 megOhm it should work with DC above the neon strike voltage.
At 10 megohm it may work.
At above 10 M it's uncertain.

Have you SEEN it work with DC yourself?
What voltage DC? What environment - bare feet? rubber shoes ... ?

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    \$\begingroup\$ +1 There's also 'DC' that is really half-wave or full-wave rectified AC and behaves somewhat similarly to AC of lesser magnitude when capacitively coupled. \$\endgroup\$ Jul 6, 2015 at 4:18
  • \$\begingroup\$ Could you write something about AC? My experience is it also depends on shoes / floor material for 240V AC. May be, this is a question of where the stray capacitance builds up. \$\endgroup\$
    – sweber
    Jul 6, 2015 at 6:27

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