*Correction: Determining Current Carrying Capability*

In the December 2009 edition of Printed Circuit Design and Fab / Circuits
Assembly magazine, I made an error in the article "Determining Current
Carrying Capability", based on the new data in IPC-2152

In trying to develop a simple method for combining the effects of various
design parameters, I recommended starting with a multiplier of 1.00 and for
each condition, adding or subtracting from it to derive the final estimate.
Since these modifiers were percentages, they should have been MULTIPLIED,
not added or subtracted.
*For example*,
if proximity to a heat-sinking plane made a difference of 20%, I subtracted
0.2 from the multiplier to get 0.8, and another 20% for a different
parameter would result in a multiplier of 0.6.
This is incorrect.
I should have multiplied the modifier by 0.8, and by 0.8 again, for a result
of 0.64

*The article has been revised*, and is available here:
http://frontdoor.biz/PCBportal/HowTo2152.pdf

To make amends for my blunder, I am offering a simple spreadsheet-based
calculator to help people work through various scenarios.
http://frontdoor.biz/PCBportal/HowTo2152.xls

Doug Brooks has developed a more accurate full-featured calculator (fusing
current, skin effect, etc) which is available from his UltraCAD website at:
http://www.UltraCAD.com <http://www.ultracad.com/>

hope this helps, and I apologize for the error,

Jack Olson


.
On Tue, Feb 2, 2010 at 9:59 AM, Mike Buetow <[log in to unmask]>wrote:

>  Hi Jack,
>
>
>
> It happens. What was the error?
>
>
>
> Mike
>
>
>
> *From:* Jack Olson [mailto:[log in to unmask]]
> *Sent:* Tuesday, February 02, 2010 10:09 AM
> *To:* Mike Buetow
> *Cc:* Pete Waddell
> *Subject:* Correction: Current Carrying Capability
>
>
>
> *Mike,*
>
>
>
> *I regret to inform you that my article contained an error.*
>
>
>
> *I will cheerfully apologize if you want to print a correction*
>
> *and I will also give the world a free calculator to make amends*
>
>
>
> *sorry,*
>
> *Jack*
>

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