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Recent content by WhyDoYouAsk

  1. WhyDoYouAsk

    about constant current source

    http://www.google.com/search?client=safari&rls=en-us&q=electroplate+%22current+source%22&ie=UTF-8&oe=UTF-8 http://www.google.com/search?client=safari&rls=en-us&q=electroplating+%22voltage+source'&ie=UTF-8&oe=UTF-8 Looks like Google bets even money on that. . .
  2. WhyDoYouAsk

    about constant current source

    Flourescents prefer constant current; the ballast converts the wall outlet voltage source into a current source. Since voltage sources can deliver ~infinite current, they have downstream circuit breakers. Compare the V-I curves for both.
  3. WhyDoYouAsk

    a +/- 0.1% meter, reading "100.00"

    Ask, and I shall receive! Thanks again.
  4. WhyDoYouAsk

    a +/- 0.1% meter, reading "100.00"

    Thanks for the link. Re: lifetime, I might have once applied to the NIST; I can't recall. It's only up the road from me.
  5. WhyDoYouAsk

    a +/- 0.1% meter, reading "100.00"

    Thanks. This may come up a lot for me, so aside from the uniform distribution assumption do you have a link for this kind of not-very-well-known info (interpreting meter tolerance specs)?
  6. WhyDoYouAsk

    a +/- 0.1% meter, reading "100.00"

    The likelihood of the true value of what you're measuring actually being 100.00 is virtually zero. There's a 95% chance the true value is between 100.10 and 99.90. There's a 68% chance the true value is between 100.05 and 99.95. Agreed?
  7. WhyDoYouAsk

    The NEC, stray voltage, and ductwork

    You can check it; measure open circuit on ductwork with respect to ground, then lay a live insulated conductor on the ductwork and repeat. If there is any AC/DC voltage at all, load it with 1, 10 or 100 ohm resistors and figure out the Thevenin equiv. source impedance. There might be 100...
  8. WhyDoYouAsk

    skin depth, 60 Hz, tubular conductor

    The ACA solutions link has a lot of info in it. With the help of a spreadsheet I have found that the (Rac/Rdc)/(Rindreact/Rdc) ratio rises more rapidly with wall thickness than a straight line relationship. This is opposite to what you'd expect with a skin effect. That is, the thicker the...
  9. WhyDoYouAsk

    The NEC in Alaska

    "Fail"meaning its service lifetime is unduly shortened? Like many other chemical reactions I'm assuming service lifetime halves for each 10? rise above ambient.
  10. WhyDoYouAsk

    The NEC in Alaska

    Thanks so far; this forum is great! While we're on the subject, is 60? a nominal value (like a 2x4 is not 2.0" x 4.0") or does the insulation actually reach that temp (I'm hoping the second option is correct)?
  11. WhyDoYouAsk

    The NEC in Alaska

    Since resi. insulation temp is fixed at 60? to 90? and ampacity is determined by I² and amb. temp., can resi. wires and thermally operated CBs in Alaska legally carry more current?
  12. WhyDoYouAsk

    skin depth, 60 Hz, tubular conductor

    I thought because most of the current @ 60Hz with this config. is trying to flow in empty space. To get the full benefit of the conductor size it should be a round conductor or greater than 18mm. . .?
  13. WhyDoYouAsk

    skin depth, 60 Hz, tubular conductor

    Since a skin depth in copper is about 9 mm at 60Hz, I expected a much higher ratio of Rac/Rdc for the pipe in question. The measurements and graphs in this thread show otherwise. Thanks, all.
  14. WhyDoYouAsk

    skin depth, 60 Hz, tubular conductor

    I'm trying to calculate the AC resistance at 60 Hz of a copper pipe with 3/4" I.D., 1/16" wall thickness, and 7/8" O.D., not near any other conductors. Can anyone step me through this? It must be several times the DC resistance but I'd like to know this AC value to at least two significant...
  15. WhyDoYouAsk

    start/run capacitors

    With a motor powered by 60Hz, does the cap see 60 Hz? Is it a sine wave? If so I may be able to measure the cap value in circuit with a DVM, an ammeter and a simple calculation.

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