**From:** Doug McKean (*dmckean@corp.auspex.com*)

**Date:** Mon Nov 13 2000 - 11:27:25 PST

**Next message:**Charles Grasso: "Re: [SI-LIST] : Connector pin pwr/gnd ratio"**Previous message:**Lyke James Civ AFRL/VSSE: "[SI-LIST] : Grounding strategies for instrumentation"**In reply to:**Doug Brooks: "[SI-LIST] : Question Re: Wire Gauge and resistivity"**Next in thread:**jrbarnes@lexmark.com: "Re: [SI-LIST] : Question Re: Wire Gauge and resistivity"

Doug Brooks wrote:

*>
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*> 1. Can someone point me to a URL that would have a spec sheet that would
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*> include the resistivity and temperature coefficient of resistivity for the
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*> type of copper used in PCB construction?
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*>
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*> 2. Can someone point me to a URL that explains how to make resistance
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*> calculations of wires at different temperatures using the temperature
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*> coefficient of resistivity. I know how to do it, but I can't find a
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*> reference that I can point to in an article to tell others how to do it.
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*>
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*> 3. What is the original derivation of the AWG (American Wire Gauge) system.
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*> There is obviously a logarithmic relationship between gauge and
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*> cross-sectional area: Wire Gauge ~ Log(1/Area) but why is that?
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There's several ...

1. Diameter in mils (1/1000 inch): Diameter = 325 / 1.123^Gage

2. Gage = INTEGER((LOG(325) - LOG(Diameter)) / LOG(1.123))

3. D = 0.3252 * e^(-0.116*gauge)

But why? Might have something mathematically to do

with the relationship of area (a power function).

Don't know.

*> How were the original gauge numbers defined?
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I think in terms of circular mils,

starting with 50 AWG with diameter of 1 mil.

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**Next message:**Charles Grasso: "Re: [SI-LIST] : Connector pin pwr/gnd ratio"**Previous message:**Lyke James Civ AFRL/VSSE: "[SI-LIST] : Grounding strategies for instrumentation"**In reply to:**Doug Brooks: "[SI-LIST] : Question Re: Wire Gauge and resistivity"**Next in thread:**jrbarnes@lexmark.com: "Re: [SI-LIST] : Question Re: Wire Gauge and resistivity"

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