HP49-50G: gallonUK conversion into l

[Gil]

HP49-50G: gallonUK conversion into liters

Where from does give HP50G
that 1GALUK is '4.546092_l',

when the official value
is 4.54609_l?

Of course, there existed a prior definition, but it was
4.546 091 879 liters.

Then why this unexplained value or rounding?

Thanks for your insight, as HP is or was almost always "right" in its choice.

[Martin Hepperle]

Wikipedia says:
Imperial gallon as re-determined in 1895 and defined in 1963
4.546091879

More specifically:
In 1963, this definition was refined as the space occupied by 10 pounds of distilled water of density 0.998859 g/mL weighed in air of density 0.001217 g/mL against weights of density 8.136 g/mL (the original "brass" was refined as the densities of brass alloys vary depending on metallurgical composition), which was calculated as 4.546091879 L to ten significant figures.[5]

The precise definition of exactly 4.54609 cubic decimetres (also 4.54609 L, ≈ 277.419433 in3) came after the litre was redefined in 1964. This was adopted shortly afterwards in Canada, and adopted in 1976 in the United Kingdom.[5]

[Gil]

I saw it, yes.

My question is why HP decided to give a rounded value, when it was possible to give all the available digits?

And why did not chose HP to use the most recent (corrected) value of simply 4.54609?

And of course the derived UK units are "wrong" by the same proportion, as the ozUK.

[Gil]

By the way, regarding "distilled water of density 0.998859 g/m"

UsingTanaka formulae,
T [°C]: 16.67 [PA]: 101325, I find instead:

Pure H²O, w/o air: 998.834528764
Pure H²O, 100% air: 998.831683784

[brouhaha]

I thought it might have come from the HP-41C Petroleum Fluids Pac, in which space was at a premium and they might have truncated some contants. According to the manual for that, it uses 4.546087, so it's unclear what reference they used for that.

Back in the day, I bought the Petroleum Fluids Pac specifically for the Unit Management System (microcode functions CON and INCON); I didn't need anything actually petroleum related. The Unit Management System, supporting fewer units, was also present in the Machine Design Pac and the Thermal & Transport Science Pac. In 2009 there was a forum thread comparing them.

See the Pac manuals for details of using the Unit Management System functions. Further background and technical information on the Unit Management System may be found in two PPC Conference Proceedings:

PPC East Coast Conference, Rockville, Mayrland, 28 March 1981, pp. 2-1 ff.
PPC Northwest Conference, Corvallis, Oriegon, August 22, 1981, pp. 11-16

These conference proceedings are both available in "CD4" of Jake Schwartz' PPC Caluclator Archive.