What stands the unit "CV" for?

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uwestoehr
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What stands the unit "CV" for?

Postby uwestoehr » Fri Jun 21, 2019 3:40 am

I just documented the units supported in expressions:
https://www.freecadweb.org/wiki/Expressions#Units

But there is one unit I could not find by searching around: "CV". Does anybody know what it means?

(I only found out that in French "CV" stands for horsepower. But why should FreeCAD support such a unit? I mean horsepower has different definitions:
https://en.wikipedia.org/wiki/Horsepower#Definitions )
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bejant
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Re: What stands the unit "CV" for?

Postby bejant » Fri Jun 21, 2019 4:27 am

uwestoehr wrote:
Fri Jun 21, 2019 3:40 am
I only found out that in French "CV" stands for horsepower. But why should FreeCAD support such a unit
I suppose it's because HP is generally still the unit of power in the U.S.

uwestoehr wrote:
Fri Jun 21, 2019 3:40 am
horsepower has different definitions
It's still the same unit of power, just expressed (defined) in different units (metric analogy is "kinda-sorta" cubic centimeters <==> milliliters)
juless
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Re: What stands the unit "CV" for?

Postby juless » Fri Jun 21, 2019 10:38 am

Just my 2 cents: could it be related to electrical charge q, as in q = C•V? The correct unit would be Coulomb (C) then though.
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papyblaise
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Re: What stands the unit "CV" for?

Postby papyblaise » Fri Jun 21, 2019 11:42 am

Hello
in French CV (capital letters) is use for the fiscal rate for exemple Citreon 2CV (fiscal) égal 14cv (minus) or HP in english
Watts is the units for power in ISO , for all mechanical engine (electric , bezin , diesel , stem)
HP or cv is must popular use for bezin or diesel engine for ex: grass mower egal 6.5 hp (or cv ) tractor =85hp , car =115hp
and Watt for electrical (radiator = 1.5kW =1500W)
wmayer
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Re: What stands the unit "CV" for?

Postby wmayer » Fri Jun 21, 2019 11:44 am

CV has been added with git commit 0a503161b69e (see also git commit 68f3a1fd) and according how it's defined it is considered as Joule (Watt second) instead of Watt.

Code: Select all

App.Units.parseQuantity("1 CV")
Returns
1e+06 mm^2*kg/s^2
which is clearly wrong according to https://en.wikipedia.org/wiki/Horsepower

So, IMO it's best to remove it.
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uwestoehr
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Re: What stands the unit "CV" for?

Postby uwestoehr » Fri Jun 21, 2019 12:49 pm

wmayer wrote:
Fri Jun 21, 2019 11:44 am
CV has been added with git commit 0a503161b69e (see also git commit 68f3a1fd) and according how it's defined it is considered as Joule.
So, IMO it's best to remove it.
Thanks. So it stands for Coulomb * Volt.
I vote to remove this since I (as physicist) have never seen this unit while in contrary the units Coulomb and Volt are missing. So when CV is removed, C and V should be added.

In the last table of https://www.freecadweb.org/wiki/Expressions#Units I collected other units FreeCAD might support as well. I opened here a discussion about missing units: https://forum.freecadweb.org/viewtopic.php?f=38&t=37164
wmayer
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Re: What stands the unit "CV" for?

Postby wmayer » Fri Jun 21, 2019 2:42 pm

Volt is here https://github.com/FreeCAD/FreeCAD/blob ... ser.l#L123 but Coulomb is indeed missing.
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uwestoehr
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Re: What stands the unit "CV" for?

Postby uwestoehr » Fri Jun 21, 2019 4:25 pm

wmayer wrote:
Fri Jun 21, 2019 2:42 pm
Volt is here https://github.com/FreeCAD/FreeCAD/blob ... ser.l#L123 but Coulomb is indeed missing.
Thanks for the link to the code. But inputting "1V" returns "Failed to parse expression." So apparently we have a bug because the unit Volt is not defined in
https://github.com/FreeCAD/FreeCAD/blob ... onParser.l
and
https://github.com/FreeCAD/FreeCAD/blob ... onParser.c
and
https://github.com/FreeCAD/FreeCAD/blob ... onParser.c

I'll try to send a patch but cannot compile yet to test if it will work.