How to: test light (not)

Discussion in 'General Electronics Chat' started by inwo, May 31, 2014.

  1. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
    Testing old corroded industrial switches can be tough with low level ohmmeter.

    Even my Simpson260 was giving me false negatives.

    So I dig out an old electricians test light that I found in a barn.

    They were pretty standard back in the day. My uncle (electrician) had on on the bench when I was about 10 years old.

    Remember asking him why he didn't get shocked lighting a 120vac bulb.

    Didn't take a little kid seriously, and for an answer he touched the probes.
    I've always wondered what was in that magic box.

    Assumed it was some type of transformer connection as there was no click from a relay.

    Today I peeked.:)
    This isn't the same one. Hope he new better.

    As per another thread. Look at the knurled nut.:D
  2. #12


    Nov 30, 2010
    What can I say?
    1) OMG?
    2) He must have had really dry hands?

    ps, I fit a probe with a .05 inch Allen wrench and grind a point on that. It pierces just about any layer of interference.
  3. MaxHeadRoom


    Jul 18, 2013
    I worked at a place once where a guy used to place the palm of his hand over the bare ends of a test lead plugged into a 120v outlet pins to see if it was live.:eek:
  4. atferrari

    AAC Fanatic!

    Jan 6, 2004
    Seen the same on board. Our Electrician, used his callused (not sure if dry but always dirty) fingertips to test the presence of 220V. :eek:
  5. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
    My dad (carpenter) had to lick his finger to find a live wire.
    Back in the day heavy callouses were the norm.:)

    Rewired it the way I thought it was to start.

    Wired the primary of a 24v transformer in series with the 60W bulb.

    Secondary to the probes.

    Now it does just what I need.

    20 ohms or more light is out.
    10 ohms = dim.
    Less than 10 = brighter.

    Had a bunch of aux. contacts to check and was bored today.:)
  6. inwo

    Thread Starter Well-Known Member

    Nov 7, 2013
    A small step away from 480 then. 277 to ground.:D

    I have never had the displeasure and always assumed it to be a fatal experience. :eek:

    Don't believe I ever got across 220 either.

    My mother tells me of the time in the 30s a traveling show came to town, offering a silver dollar to anyone picking it from the bottom of a electrified bucket of water.

    Dad was able to do it. I believe the story as in the fifties he pinned the needle on one of those arcade shockers. He told the operator it wasn't working.:eek:
  7. atferrari

    AAC Fanatic!

    Jan 6, 2004
    Not with a knife but with what I believe was a knitting needle, I did what you show in your avatar. I think I was 5 or 6 yo and the radio was unplugged so the socket, all for me!

    A nasty shock!
  8. RichardO

    Well-Known Member

    May 4, 2013
    The skin resistance varies a _lot_ from person to person.

    I had a continuity tester at work that used a Sonalert and a 9 volt battery. I could not make it beep by putting the probes between my fingers so close they almost touched. One day a co-worker borrowed my tester. He picked it up with one probe in each hand and it was beeping as he walked away! I have always wondered if he would trip a circuit breaker if he got across the power line. ;-)