Re: [SI-LIST] : Heating resistor: RMS or average current (was Re: Effect of low Zo for unterminated lines)

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From: add automation (add.automation@sympatico.ca)
Date: Tue Oct 26 1999 - 07:13:00 PDT


Larry Miller wrote:
>
> RMS IS the heating effect in terms of watts; good RMS meters use bolometers
> to measure it with. "Average" is the wrong answer.
>
> If you want to know how hot a resistor will get you need a model of its
> heat flow, conduction, and radiation. You have to come up with an
> equivalent Theta(case-to-ambient). I think this kind of info is fairly
> readily available for common resistor types and is easily measured with DC
> in any case. Then the temperature rise is simply P(rms) *
> Theta(case-to-ambient). Dimensional check: Watts * Deg/Watt = Deg.
>
> Larry Miller

[...]

  For more info, HP has a very comprehensive app note on RF power
  measurement at

    http://www.tmo.hp.com/tmo/Notes/English/5965-6630E.html

  Sorry if this is a duplicate posting - my ISP disconnected on the
  previous attempt, so I don't know if it succeeded.

Best Regards,

Michael R. Monett
mailto:add.automation@sympatico.ca

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