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'[EE] Sizes, was Digital camera sensor sizes'
2005\12\05@094005 by Tony Smith

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> Russell McMahon wrote:
>
> > Explains the relationship between the rubbish sensor size that makers
> > usually use (and why they feel they can get away with using it) and
> > actual size.
>
> Don't ever trust a size given in inches (unless you know the specific logic
> that was used to create it :)
>
> 21" screens that are not 21", 2" by 4" logs that are not 2" by 4"


21" screens are 21", it just that the bit you see isn't.  They measure the tube, not the viewable area (but I figure you know this
:-) )  LCD are different.

2" by 4" lumber is that size before it's dressed.  One day I'll find out why they still call it that...

Conversion to metric has made a few amusing things happen.  If you buy a 6' piece of lumber, you'll find it's a bit short.  They
rounded the measurements off, so the old 6' is now 180cm, a few cm short (was ~183cm).

Tony

2005\12\05@095308 by Mike Hord

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> 2" by 4" lumber is that size before it's dressed.  One day
> I'll find out why they still call it that...

Brevity.  2 by 4 is easier than 1 and 7/16 by 3 and 3/4!

Pipe is another one.  Take a tape measure to some 1.5"
PVC pipe sometime...

Mike H.

2005\12\05@102254 by Tony Smith

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> > 2" by 4" lumber is that size before it's dressed.  One day
> > I'll find out why they still call it that...
>
> Brevity.  2 by 4 is easier than 1 and 7/16 by 3 and 3/4!
>
> Pipe is another one.  Take a tape measure to some 1.5"
> PVC pipe sometime...
>
> Mike H.


I kinda figured laziness played a big part in the 4x2 saga.

Now, I know why pipes are funny sizes.  The sizes came from copper pipes (possibly iron), and were originally the proper sizes.
That is, a 1" pipe was 1".  Then people figured out that with better material, you could use less of it, so the pipe walls got
thinner.  The inside diameter stayed the same so the fittings still, well, fit.

When PVC came along, they made it the same size as what was in use (which made sense), and gave it the same name, (which also makes
sense).  I guess.

I've actually got a few bits of 1/2" pipe in from of me, only one is actually 1/2".  It's fairly old though.

Tony

2005\12\05@130610 by Walter Banks

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It is even worse than that about 2x4's we can buy 2x4's that are 2" x 4" and ones that are 1 7/16 by 3 3/4 both are called 2 x 4 "s.

w..


Mike Hord wrote:

> > 2" by 4" lumber is that size before it's dressed.  One day
> > I'll find out why they still call it that...
>
> Brevity.  2 by 4 is easier than 1 and 7/16 by 3 and 3/4!
>
> Pipe is another one.  Take a tape measure to some 1.5"
> PVC pipe sometime...
>
> Mike H.
>
> -

2005\12\05@132526 by David Van Horn

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>
> It is even worse than that about 2x4's we can buy 2x4's that are 2" x
4"

"Dimensional" lumber.

> and ones that are 1 7/16 by 3 3/4 both are called 2 x 4 "s.

Regular lumber.



It's a PITA, ain't it?



2005\12\05@145621 by Gerhard Fiedler

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David Van Horn wrote:

> It's a PITA, ain't it?

/Everything/ is better than using the correct measurement in
easy-to-calculate-with units -- just about everybody can do that. Must have
to do with trade unions... :)

Gerhard

2005\12\05@154320 by Gerhard Fiedler

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Tony Smith wrote:

> 21" screens are 21", it just that the bit you see isn't.  They measure
> the tube, not the viewable area (but I figure you know this
> :-) )  

You kind of figured right -- that's why I wrote "screen" and not "tube". I
don't look at tubes, in general. Using the tube measurement makes about as
much sense (or less?) than using the case outside measurement. Thing is
they don't sell monitors with x" tubes, they sell x" monitors which don't
have x" to be measured anywhere on them...

But... that's what they say (that it's the measurement of the tubes). Given
my experience with inch-based specifications, I actually doubt the tube
itself in fact measures x" diagonal, to any reasonable tolerance :)  Did
someone check any?

> LCD are different.

Most are designed in Asia, part of "metric land". That's why there's hope
:)

Gerhard

2005\12\05@175208 by olin piclist

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Walter Banks wrote:
> It is even worse than that about 2x4's we can buy 2x4's that are 2" x
> 4" and ones that are 1 7/16 by 3 3/4 both are called 2 x 4 "s.

Note quite.  The first are called "rough cut" and the second "dimensional".
Most "home center" type stores only sell dimensional.  I usually buy rough
cut from a local saw mill.  Keep in mind though that there is a reason the
extra wood is shaved off, and only use rought cut if that isn't going to
cause trouble or if you're willing to do the shaving yourself if you need
to.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\05@175439 by olin piclist

face picon face
David Van Horn wrote:
>> It is even worse than that about 2x4's we can buy 2x4's that are 2"
>> x 4"
>
> "Dimensional" lumber.

No, dimensional refers to the piece after it's milled.  The original true
2x4 inch piece is called "rough cut".


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\05@182814 by Howard Winter

face
flavicon
picon face
Olin,

On Mon, 5 Dec 2005 17:54:36 -0500, Olin Lathrop wrote:

> David Van Horn wrote:
> >> It is even worse than that about 2x4's we can buy 2x4's that are 2"
> >> x 4"
> >
> > "Dimensional" lumber.
>
> No, dimensional refers to the piece after it's milled.  The original true
> 2x4 inch piece is called "rough cut".

Or in the UK, "planed" and "sawn" respectively.  But ours is measured in mm nowadays, and the measurements
seem to be much closer to the actual size than when they were in inches.

Cheers,



Howard Winter
St.Albans, England


2005\12\05@183131 by Howard Winter

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Gerhard,

On Mon, 5 Dec 2005 18:41:00 -0200, Gerhard Fiedler wrote:
>...
> > LCD are different.
>
> Most are designed in Asia, part of "metric land". That's why there's hope :)

Except that they are still measured in inches!  The 18" Dell LCD I'm looking at really does measure 18" on the
viewable diagonal.

Cheers,


Howard Winter
St.Albans, England


2005\12\05@203358 by Gerhard Fiedler

picon face
Howard Winter wrote:

>> Most are designed in Asia, part of "metric land". That's why there's
>> hope :)
>
> Except that they are still measured in inches!  The 18" Dell LCD I'm
> looking at really does measure 18" on the viewable diagonal.

Yes, I know, that's why it still only hope :)

And those are no real inches anymore. They are marketing inches only. That
takes a lot off their edge... and makes that they correspond to a
measurement one can make :)

Gerhard

2005\12\06@065822 by Lee Jones

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face
>> 21" screens are 21", it just that the bit you see isn't.  They
>> measure the tube, not the viewable area (but I figure you know
>> this > :-) )  

> You kind of figured right -- that's why I wrote "screen" and not
> "tube". I don't look at tubes, in general. Using the tube measurement
> makes about as much sense (or less?) than using the case outside
> measurement. Thing is they don't sell monitors with x" tubes, they
> sell x" monitors which don't have x" to be measured anywhere on them...
>
> But... that's what they say (that it's the measurement of the tubes).
> Given my experience with inch-based specifications, I actually doubt
> the tube itself in fact measures x" diagonal, to any reasonable
> tolerance :)  Did someone check any?

Yes.  But it has been many years.  And the tolerance isn't tight. :-)

The diagonal measurement of cathode ray tubes was used as a marketing
tactic for television sets and goes back at least 40 years (that I can
attest to).  It may have made a little sense way back when TV pictures
were almost circular varying to almost retangular.  Even when they were
rectangular, the aspect ratio certainly wasn't as standardized as now.

                                               Lee Jones

2005\12\06@082300 by Gerhard Fiedler

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Lee Jones wrote:

> It may have made a little sense way back when TV pictures were almost
> circular [...]

That's probably the most enlightened explanation of the monitor sizes I've
read so far :)

Gerhard

2005\12\06@141412 by Peter

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On Mon, 5 Dec 2005, David Van Horn wrote:

{Quote hidden}

Switch to metric and when you ask for 180cm modules you get 180cm
modules ;-)

Peter

2005\12\06@161906 by Peter

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On Tue, 6 Dec 2005, Gerhard Fiedler wrote:

> Lee Jones wrote:
>
>> It may have made a little sense way back when TV pictures were almost
>> circular [...]
>
> That's probably the most enlightened explanation of the monitor sizes I've
> read so far :)

Except the first TVs used scope screens and, as you know, non-flat scope
screens have an un-usable edge zone. That's probably when things started
going bad ...

Peter

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