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    Hazardous-voltage primer

    Hazardous-voltage primer
    Understanding the hazards associated with voltage and knowing the principles
    of safety and the importance of certification are the keys to safe design
    and product use. Even low voltage is hazardous and can damage products and
    harm users.
    By David Lohbeck, National Instruments -- EDN, 5/11/2006
    It is common knowledge that wall-outlet voltages of 120V in the
    United States and 230V in Europe can cause severe shock or death, but did
    you know that many people consider 120 and 230V to be low-voltage? Believe
    it or not, according to most standards, voltages less than or equal to 1000V
    are low. Voltages greater than 1000V are high and are not commonplace in the
    typical home or workplace. More specifically, peak voltage greater than
    42.4V is hazardous; voltage less than or equal to 42.4V, or SELV (safety
    extra-low voltage), is nonhazardous. It is difficult to know when
    electricity can cause serious injury or be fatal.
    PeteS in CA

    Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
    ****************************
    To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
    ****************************

    #2
    Re: Hazardous-voltage primer

    It's amazing were still alive.
    Warning stickers are good.
    Monitors are notorius for zapping people.
    Jim

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      #3
      Re: Hazardous-voltage primer

      Originally posted by arneson
      It's amazing were still alive.
      Warning stickers are good.
      Monitors are notorius for zapping people.
      monitors are far from the most dangerous item in a normal home.
      watch out for the nuker!
      transformer secondary up to 4000vac.
      a guy i fix stuff for told a relative in ky to stay out of the works of one and wait till it could be brought up here to me.would not listen and now qualifies for a darwin award.

      Comment


        #4
        Re: Hazardous-voltage primer

        Fluke 1AC-E Voltalert and 1000v insulated screwdriver



        Attached Files
        capacitor lab yachtmati techmati

        Comment


          #5
          Re: Hazardous-voltage primer

          As important as the voltage/current involved is the nature of the current:

          From Basic Res. Cardiol. 78, 604-616 (1983): graph showing fibrillation threshold in mA vs. frequency of sinusoidal AC:




          Note how the most lethal AC frequency is around 30Hz, although as you can see 50-60Hz isn't much safer. This experiment was carried out on isolated heart tissue - in "real life" the highest AC frequencies are even less likely to cause VF due to their reduced degree of penetration into the body.


          ....

          PS. If any of you are interested, let me know and I can forward you the "full text" of the experiment.
          Attached Files
          Last edited by tiresias; 05-18-2006, 06:22 AM.

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            #6
            Re: Hazardous-voltage primer

            I can tell you from experience first hand that the ring voltage on a telephone line is quite painful - when the wire is in your mouth.

            The microwave is definitely lethal with 2kV at 500mA most common. Neon sign transformers at 15kV and 60mA are extremely dangerous. Put some caps across the output and the arcing is deafening. Ask any tesla coiler that's used a pole pig in reverse - stepping up 240v "house power" to 13kV or higher - often at currents over 1 AMP! Makes the lights dim in the neighborhood. Touch that and you'll be riding in a Caddie for a dirtnap.

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              #7
              Re: Hazardous-voltage primer

              Air conditioners have nailed me a couple of times.
              Those are big caps and compressors are high current.
              Jim

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