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PTC (positive Thermo coefficient) device temp ratings.

Discussion in 'Electronic Design' started by martin griffith, Dec 20, 2005.

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  1. I've only collided with NTC's occasionally, do a search for siemens
    matushita B57164 data sheet, gives a lot of numbers, in centigrade,
    they seem to be referenced to 25C


    martin
     
  2. One kind of PTC is essentially a thermal switch that changes from a
    low resistance state (that varies very little over a wide range of
    temperatures) below the switching temperature to a very much higher
    resistance, above the switching temperature. They are intended to
    either detect which side of a single temperature they are on (or
    provide a very sensitive temperature measurement over a narrow range
    of temperatures), or are intended to act as self resetting fuses.

    Those intended as fuses are specified in terms of their switch off
    time versus current and temperature:
    http://www.littelfuse.com/data/en/Data_Sheets/30R.pdf

    Those intended as temperature detectors are specified with a curve of
    resistance versus temperature, and usually a switching temperature
    (the temperature at the steepest point on the resistance curve).
    http://www.epcos.com/inf/55/db/ptc_03/01870189.pdf
     
  3. Jamie

    Jamie Guest

    this has alluded me for a while since
    i can not seem to find the temperature
    at which the manufactures state their
    PTC or NTC. etc..
    for example
    i have a PTC rated for 100 ohms cold!
    now what temp is that?
    hell, it's 55F here in the shack and i
    am cold now! does that apply? :)
    just like to know what temp they are
    referring to !
     
  4. They refer to 25 DegC, there should be an
    online translator to be found on the
    internet, I guess.

    Rene
     
  5. Now, there's a concept. The tire bomb. Just drop the tire in a tub of LN2,
    and fill it up with air - hey, wait a minute, won't the O2 condense out
    at LN2 temps? Hmmm... Anyway, set it where you want the explosion to be,
    and walk away. The nitrogen boils off, the air in the tire expands, and,
    BLOOEY! ;-p
     
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