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HP Forum Archive 18

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Constants in the HP35S
Message #1 Posted by J-F Garnier on 11 Nov 2007, 11:32 a.m.

I noticed that the physics constants in the HP35S are slightly different from my other "reference" machines. Several values are just changed by less than 1ppm, but some constants exhibit more important deviations:

	HP35S		reference machines
G	6.673E-11	6.67259E-11
k	1.3806503E-23	1.380658E-23
R	8.314472	8.314510

reference machines:
HP48SX with HP Solve Eq Lib
HP48GX
HP49G+ (2.01-2)
TI89 with EE-Pro 1.1

The biggest relative difference is found for the constant of gravitation. As G is not known very well, it seems that it's now a rounded value. The values of the Boltzmann constant k and molar gas constant R are changed by several ppm.

I don't know for the HP50. Was it updated with new constant values too?

J-F

Edited: 11 Nov 2007, 11:35 a.m.

      
Re: Constants in the HP35S
Message #2 Posted by James M. Prange (Michigan) on 11 Nov 2007, 2:16 p.m.,
in response to message #1 by J-F Garnier

Quote:
I don't know for the HP50. Was it updated with new constant values too?
No, it uses the same ROM, equation libraries, and periodic table library as the 49g+. For that matter, with a few simple tricks, this ROM (although without the Saturn+ speed-up tweaks) can be used on the 49G as well.

The equation and periodic table libraries are ports of the libraries on the Solve Eq Lib card for the 48SX, and as far as I know, no constants were changed. In particular:

G: 6.67259E-11_m^3/(s^2*kg)     G: 3.32208E-11_lbf*ft^2/lb^2
k: 1.380658E-23_J/K             k: 7.270063E-27_Btu/°R
R: 8.31451_J/(gmol*K)           R: 10.73164_psi*ft^3/(lbmol*°R

Does anyone know whether any "constants" have been "officially" revised from what they were when the 48SX was current?

By the way, if you're using ROM revision 2.01-2, then I recommend upgrading to either the latest "official" ROM, Version C Revision #2.09 (build 92) (but use the newer libraries), or maybe the newer "unofficial" Version G Revision #2.10-7 (Build 93).

Regards,
James

            
Re: Constants in the HP35S
Message #3 Posted by Ken Shaw on 12 Nov 2007, 11:42 a.m.,
in response to message #2 by James M. Prange (Michigan)

According to NIST (least sig. digits uncertainty in parentheses)

http://www.physics.nist.gov

G is 6.67428 (67)

k is 1.3806504 (24)

R is 8.314472 (15)

                  
Re: Constants in the HP35S
Message #4 Posted by Dave Shaffer (Arizona) on 12 Nov 2007, 3:15 p.m.,
in response to message #3 by Ken Shaw

If you click a few layers deeper, to codata ref you will see the magic term "CODATA internationally recommended values."

These values are the result of an occasional (every few years) least-squares adjustment of all the latest experimental determinations of physical constants. The results become the values recommended for all scientific uses. In this case, the latest fit took place in 2006. If you want your HP 48/49/50 results to agree with the rest of the world, you should use the CODATA values. For all you error analysis junkies, note that all constants also have an error estimate. (A few constants, like the speed of light, are given/defined to have an exact value.)

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