Convert Function

rmace

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Jul 9, 2007, 9:12:01 PM7/9/07

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There is an error in EXCEL 2002 convert function for BTU to flb.

1 BTU should convert to 778 flb; however, it is calculating 25037.

Can someone else confirm this error?

Thank you.
--
Bob

Vasant Nanavati

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Jul 9, 2007, 9:56:29 PM7/9/07

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I can confirm this error in Excel 2003 as well.
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Duke Carey

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Jul 10, 2007, 12:56:02 PM7/10/07

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And in 2007

Dana DeLouis

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Jul 10, 2007, 1:39:00 PM7/10/07

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I would just be guessing here.
=CONVERT(1,"btu","flb")
25036.98

In my old "Handbook of Chemistry & Physics"
the closest conversion listed is
Btu to "Foot-Poundals", and listed as 25020.1

Hmmm. Still a little off.

However, if I flip the page, and reverse the conversion, the factor given is
a little less precise...
0.0000399417

but
=1/0.0000399417
returns
25,036.49

Much closer. So, my guess is that Microsoft copied the wrong conversion,
and didn't use enough digits.
--
Dana DeLouis

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rmace

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Jul 10, 2007, 9:36:04 PM7/10/07

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I have checked several physics and thermodynamic references.
2 of them say 1 BTU = 778 foot pounds.
1 says 1 BTU = 778.3 foot pounds.
1 says 1 BTU = 1060 joules and 1 foot pound = 1.36 joules
which works out to 1 BTU = 779.411 foot pounds.
1 says 1 foot pound = . .001286 BTU
which works out to 1 BTU = 777.605 foot pounds.
A poundal is different than a pound by a factor of the gravitational constant
g = approx 32.2
And the error factor here is approximately = 32.2
Therefore if EXCEL actually meant foot-poundals, instead of foot-pounds,
then there conversion is correct; however, their reference for the convert
function says “foot pounds” and not “foot poundals”. In engineering
practice, “foot-poundals” are seldom used, “foot pounds” are the normal
measurement for energy.

So, maybe, the EXCEL code writers were confused on the units when they wrote
the convert code??

Thank you for your responses. I will send an email to microsoft support.
--
Bob

Dana DeLouis

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Jul 11, 2007, 2:26:46 PM7/11/07

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Hi. This sure is a confusing conversion.
I learned a little something in a math program.
I was using Foot Pounds, and was flagged with the message "
Incompatible units"

? "SI"
SI[expr] converts expr to SI units (International System)

I had to use the correct unit of Force, and move it 1 foot to get the
conversion.
The newer software version seems to have a logic bug since I had to use
Convert.
SI[BTU/Convert[1*Foot*PoundForce, Joule]]

778.172603790403

If I use "Poundal", I seem to get Excel's conversion factor.

SI[BTU/Convert[Foot*Poundal, Joule]]

25036.945785921285

So, It does appear to me that Excel is using the wrong units of Force.

--
HTH :>)
Dana DeLouis
Windows XP & Excel 2007

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