Godamned 0603...

[olaf]

John Larkin <jlarkin@highland_atwork_technology.com> wrote:

Surprisingly, some big aerospace companies still use pounds and slugs
and BTUs and things. Creeps me out.

Yes, it must be a strange live there. We have in our measurement devices
a huge list to calculate the units for US customers. When you read this
it is very strange that they claim to reach the moon. :-D

Oh..and it is one of the reason why american cars are not so popular
in Germany. People wonder how to repair them with strange threads
and unusual tools.

Whenever I read about AWG, 0.5oz copper or number drill sizes I have
to shake my head.

Olaf

 

[Piotr Wyderski]

jlarkin@highlandsniptechnology.com wrote:

> Then there are the sideways caps, like 0306.

And resistors. I like the 0612 for current sensing.

Best regards, Piotr

 

[David Brown]

On 18/02/2022 23:36, Rick C wrote:

On Friday, February 18, 2022 at 1:51:04 PM UTC-5, whit3rd wrote:
On Friday, February 18, 2022 at 6:45:50 AM UTC-8,

You mean why do people use the measuring system that everyone
else in their country use? I guess this is a more pointed
question at the US community. I remember working with a
mechanical engineer at a military contractor and was surprised
they still did everything using inches. 90% of electronic
components are in mm as the primary unit. I guess I expect the
mechanical community would have converted by now, but, no.
Pre-NATO, all US military machinery would have been inches; even
now, NATO has standard 7.62 mm ammo, which is just a
soft-conversion from .30 caliber...

I would hope you\'d understand the difference in changing nomenclature
and changing measurement systems. Caliber is not an actual
measurement of anything, rather a nominal use. Same as 12 inch
wafers or a 19 inch rack cabinet. I guess something on a 19 inch
rack cabinet is actually 19 inches, but in reality, it\'s just a name
we use.

I think a key point on units is whether you need to convert them or not,
and how they are compared to different measurements. If you need to
convert things into real lengths, weights, or whatever, then metric is
the only sane choice. But often you don\'t need conversions.

It doesn\'t matter if a .44 calibre bullet is 0.44 inches wide or long,
0.44 kg in weight, or whatever - it\'s just a name, and as long as you
match up the name used on the gun and the ammo, you\'re fine.

It doesn\'t matter what width a 19\" rack is - it just matters that
everyone follows the same standard size. You don\'t measure the height
of the rack in centimetres - you measure it in \"units\" because
everything that goes in the rack is an integer number of \"units\" in
height. If you want to know if your new 4 unit server will fit in your
rack, you count the number of units of space you have left - conversion
to millimetres or measuring with an inchtape would be silly.

On the other side, the size of your pcb tracks and footprints, or screw
threads, or mechanical drawings, all need to be as accurate as
practically possible, and all need to be specified in a precise scale -
metric.

 

[David Brown]

On 19/02/2022 01:34, John Larkin wrote:

On Fri, 18 Feb 2022 18:38:32 -0500, Joe Gwinn <joegwinn@comcast.net
wrote:

On Fri, 18 Feb 2022 23:13:26 +0000, Clive Arthur
clive@nowaytoday.co.uk> wrote:


We need to make 16 the default number base. You know it makes sense.

Hard to count on the fingers?

Some cultures use additional parts of their hand (or even the rest of
their body) in counting.

Base 12 has been proposed to replace 10.

Base 12 has been used for many things - that\'s why we have \"a dozen\" and
\"a gross\". Base 20 has also been popular (hence \"a score\"). And mixes
of bases have been used historically - the Sumerians and Babylonians
alternated between 12 and 5, giving 60 per digit pair, from whence 60
seconds in a minute, 60 degrees in a triangle.

But for larger numbers, a consistent base is a lot easier. Either 12 or
16 might have been a better choice than 10, but it\'s hard to change now!


I\'d prefer base 16 - it makes calculating the digits of π easier

 

[Rick C]

On Saturday, February 19, 2022 at 6:17:25 AM UTC-5, David Brown wrote:

On 18/02/2022 23:36, Rick C wrote:
On Friday, February 18, 2022 at 1:51:04 PM UTC-5, whit3rd wrote:
On Friday, February 18, 2022 at 6:45:50 AM UTC-8,
You mean why do people use the measuring system that everyone
else in their country use? I guess this is a more pointed
question at the US community. I remember working with a
mechanical engineer at a military contractor and was surprised
they still did everything using inches. 90% of electronic
components are in mm as the primary unit. I guess I expect the
mechanical community would have converted by now, but, no.
Pre-NATO, all US military machinery would have been inches; even
now, NATO has standard 7.62 mm ammo, which is just a
soft-conversion from .30 caliber...

I would hope you\'d understand the difference in changing nomenclature
and changing measurement systems. Caliber is not an actual
measurement of anything, rather a nominal use. Same as 12 inch
wafers or a 19 inch rack cabinet. I guess something on a 19 inch
rack cabinet is actually 19 inches, but in reality, it\'s just a name
we use.

I think a key point on units is whether you need to convert them or not,
and how they are compared to different measurements. If you need to
convert things into real lengths, weights, or whatever, then metric is
the only sane choice. But often you don\'t need conversions.

It doesn\'t matter if a .44 calibre bullet is 0.44 inches wide or long,
0.44 kg in weight, or whatever - it\'s just a name, and as long as you
match up the name used on the gun and the ammo, you\'re fine.

It doesn\'t matter what width a 19\" rack is - it just matters that
everyone follows the same standard size. You don\'t measure the height
of the rack in centimetres - you measure it in \"units\" because
everything that goes in the rack is an integer number of \"units\" in
height. If you want to know if your new 4 unit server will fit in your
rack, you count the number of units of space you have left - conversion
to millimetres or measuring with an inchtape would be silly.

On the other side, the size of your pcb tracks and footprints, or screw
threads, or mechanical drawings, all need to be as accurate as
practically possible, and all need to be specified in a precise scale -
metric.

That is an error. There is nothing more precise about metric than imperial units. It\'s just a matter of convenience. For some metric is more convenient because it\'s what they are used to, but also the advantages of a decimal based system with few conversion factors. For others imperial is what they are used to and need to learn the conversion factors... many conversion factors... many, many conversion factors. But both are equally precise.

--

Rick C.

-+- Get 1,000 miles of free Supercharging
-+- Tesla referral code - https://ts.la/richard11209

 

[David Brown]

On 19/02/2022 15:15, Rick C wrote:

On Saturday, February 19, 2022 at 6:17:25 AM UTC-5, David Brown
wrote:
On 18/02/2022 23:36, Rick C wrote:
On Friday, February 18, 2022 at 1:51:04 PM UTC-5, whit3rd wrote:

On Friday, February 18, 2022 at 6:45:50 AM UTC-8,
You mean why do people use the measuring system that everyone
else in their country use? I guess this is a more pointed
question at the US community. I remember working with a
mechanical engineer at a military contractor and was
surprised they still did everything using inches. 90% of
electronic components are in mm as the primary unit. I guess
I expect the mechanical community would have converted by
now, but, no.
Pre-NATO, all US military machinery would have been inches;
even now, NATO has standard 7.62 mm ammo, which is just a
soft-conversion from .30 caliber...

I would hope you\'d understand the difference in changing
nomenclature and changing measurement systems. Caliber is not an
actual measurement of anything, rather a nominal use. Same as 12
inch wafers or a 19 inch rack cabinet. I guess something on a 19
inch rack cabinet is actually 19 inches, but in reality, it\'s
just a name we use.

I think a key point on units is whether you need to convert them or
not, and how they are compared to different measurements. If you
need to convert things into real lengths, weights, or whatever,
then metric is the only sane choice. But often you don\'t need
conversions.

It doesn\'t matter if a .44 calibre bullet is 0.44 inches wide or
long, 0.44 kg in weight, or whatever - it\'s just a name, and as
long as you match up the name used on the gun and the ammo, you\'re
fine.

It doesn\'t matter what width a 19\" rack is - it just matters that
everyone follows the same standard size. You don\'t measure the
height of the rack in centimetres - you measure it in \"units\"
because everything that goes in the rack is an integer number of
\"units\" in height. If you want to know if your new 4 unit server
will fit in your rack, you count the number of units of space you
have left - conversion to millimetres or measuring with an inchtape
would be silly.

On the other side, the size of your pcb tracks and footprints, or
screw threads, or mechanical drawings, all need to be as accurate
as practically possible, and all need to be specified in a precise
scale - metric.

That is an error. There is nothing more precise about metric than
imperial units.

I know that, and it is not actually what I said.

If everyone used imperial units consistently (which could work for
lengths, though some imperial units are different in different
countries), they could be precise.

But they don\'t - and conversions back and forth will mean inaccuracies
creep in and rounding errors can add up.

When accuracy is important, the world uses metric - except for a
decreasing proportion of hold-outs in the USA. If your drawings,
designs or measurements pass through the hands of imperial unit users in
the USA, accuracy is likely to drop.

It is not just important that you use a precise scale - some imperial
scales are as precise as metric. (An inch is formally defined as 25.4
mm.) But you need to use a /single/ scale - the same scale everyone
else uses. Metric.

It\'s just a matter of convenience. For some metric
is more convenient because it\'s what they are used to, but also the
advantages of a decimal based system with few conversion factors.
For others imperial is what they are used to and need to learn the
conversion factors... many conversion factors... many, many
conversion factors. But both are equally precise.

 

[Rick C]

On Saturday, February 19, 2022 at 9:27:22 AM UTC-5, David Brown wrote:

On 19/02/2022 15:15, Rick C wrote:
On Saturday, February 19, 2022 at 6:17:25 AM UTC-5, David Brown
wrote:
On 18/02/2022 23:36, Rick C wrote:
On Friday, February 18, 2022 at 1:51:04 PM UTC-5, whit3rd wrote:

On Friday, February 18, 2022 at 6:45:50 AM UTC-8,
You mean why do people use the measuring system that everyone
else in their country use? I guess this is a more pointed
question at the US community. I remember working with a
mechanical engineer at a military contractor and was
surprised they still did everything using inches. 90% of
electronic components are in mm as the primary unit. I guess
I expect the mechanical community would have converted by
now, but, no.
Pre-NATO, all US military machinery would have been inches;
even now, NATO has standard 7.62 mm ammo, which is just a
soft-conversion from .30 caliber...

I would hope you\'d understand the difference in changing
nomenclature and changing measurement systems. Caliber is not an
actual measurement of anything, rather a nominal use. Same as 12
inch wafers or a 19 inch rack cabinet. I guess something on a 19
inch rack cabinet is actually 19 inches, but in reality, it\'s
just a name we use.

I think a key point on units is whether you need to convert them or
not, and how they are compared to different measurements. If you
need to convert things into real lengths, weights, or whatever,
then metric is the only sane choice. But often you don\'t need
conversions.

It doesn\'t matter if a .44 calibre bullet is 0.44 inches wide or
long, 0.44 kg in weight, or whatever - it\'s just a name, and as
long as you match up the name used on the gun and the ammo, you\'re
fine.

It doesn\'t matter what width a 19\" rack is - it just matters that
everyone follows the same standard size. You don\'t measure the
height of the rack in centimetres - you measure it in \"units\"
because everything that goes in the rack is an integer number of
\"units\" in height. If you want to know if your new 4 unit server
will fit in your rack, you count the number of units of space you
have left - conversion to millimetres or measuring with an inchtape
would be silly.

On the other side, the size of your pcb tracks and footprints, or
screw threads, or mechanical drawings, all need to be as accurate
as practically possible, and all need to be specified in a precise
scale - metric.

That is an error. There is nothing more precise about metric than
imperial units.
I know that, and it is not actually what I said.

Uh, really???

\"all need to be specified in a precise scale - metric\"

Perhaps I\'m starting to forget my English.

If everyone used imperial units consistently (which could work for
lengths, though some imperial units are different in different
countries), they could be precise.

The precision of a unit has nothing to do with who is using it.

But they don\'t - and conversions back and forth will mean inaccuracies
creep in and rounding errors can add up.

Ok, now you are on a different topic, unit conversions. But the fact remains that there is nothing about metric that is more precise than imperial units.

When accuracy is important, the world uses metric - except for a
decreasing proportion of hold-outs in the USA. If your drawings,
designs or measurements pass through the hands of imperial unit users in
the USA, accuracy is likely to drop.

BS! The conversion is simple, 2.54 cm to the inch, exactly, or should I say, \"precisely\"?

It is not just important that you use a precise scale - some imperial
scales are as precise as metric. (An inch is formally defined as 25.4
mm.) But you need to use a /single/ scale - the same scale everyone
else uses. Metric.

Now you are doubling down on your bad bet! You claimed you weren\'t saying metric is more precise than imperial and now you are saying it is!

BTW, you need to understand precision. It\'s actually a term that is being misused by you. What exactly do you mean when you say \"precision\"? Precision has to do with repeatability of a measurement relating to effects of equipment in the real world. This has *nothing* to do with what scale you are using.

Please stop being silly about this. There\'s nothing inherently more \"precise\" about metric than imperial. I hope you also realize that every specification has a tolerance. This is clearly shown in drawings when they are dimensioned in both imperial and metric units.

--

Rick C.

-++ Get 1,000 miles of free Supercharging
-++ Tesla referral code - https://ts.la/richard11209

 

[server]

On Sat, 19 Feb 2022 08:14:14 +0100, Piotr Wyderski
<bombald@protonmail.com> wrote:

jlarkin@highlandsniptechnology.com wrote:

Then there are the sideways caps, like 0306.

And resistors. I like the 0612 for current sensing.

Best regards, Piotr

Resistor power dissipation doesn\'t vary much between part sizes like
0603, 0805, 1206, provided you can heat sink the end caps. Sinking is
limited by the pcb pads. If you do big copper pours, thermal crowding
limits heat spreading. So the sideways parts are better, specifically
for current shunts on big copper pours.

One can also parallel a few resistors and place a couple of strategic
pickoff vias.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1



--

I yam what I yam - Popeye

 

[Jeroen Belleman]

On 2022-02-19 12:27, David Brown wrote:

On 19/02/2022 01:34, John Larkin wrote:
On Fri, 18 Feb 2022 18:38:32 -0500, Joe Gwinn <joegwinn@comcast.net
wrote:

On Fri, 18 Feb 2022 23:13:26 +0000, Clive Arthur
clive@nowaytoday.co.uk> wrote:


We need to make 16 the default number base. You know it makes sense.

Hard to count on the fingers?


Some cultures use additional parts of their hand (or even the rest of
their body) in counting.

Base 12 has been proposed to replace 10.

Base 12 has been used for many things - that\'s why we have \"a dozen\" and
\"a gross\". Base 20 has also been popular (hence \"a score\"). And mixes
of bases have been used historically - the Sumerians and Babylonians
alternated between 12 and 5, giving 60 per digit pair, from whence 60
seconds in a minute, 60 degrees in a triangle.

But for larger numbers, a consistent base is a lot easier. Either 12 or
16 might have been a better choice than 10, but it\'s hard to change now!


I\'d prefer base 16 - it makes calculating the digits of π easier

Base 12 is good because it has lots of dividers. To make learning
multiplication tables easier, I would choose the digit values to
go from -5 to +6 rather than from 0 to 11. That has lots of other
advantages too. (Maybe from -6 to +6 is even better for symmetry,
although then there would be numbers that could be written in
multiple ways.)

Jeroen Belleman

 

[server]

On Sat, 19 Feb 2022 06:22:16 +0100, olaf <olaf@criseis.ruhr.de> wrote:

John Larkin <jlarkin@highland_atwork_technology.com> wrote:

Surprisingly, some big aerospace companies still use pounds and slugs
and BTUs and things. Creeps me out.

Yes, it must be a strange live there. We have in our measurement devices
a huge list to calculate the units for US customers. When you read this
it is very strange that they claim to reach the moon. :-D

Oh..and it is one of the reason why american cars are not so popular
in Germany. People wonder how to repair them with strange threads
and unusual tools.

Whenever I read about AWG, 0.5oz copper or number drill sizes I have
to shake my head.

Olaf

Those everyday units, inches and tablespoons and cups and miles per
hour, are familiar and no trouble at all. We do engineering math in SI
units. I do sometimes compute things like degC/W per inch. Here are
some measurements of the thermal conductivity of some coaxial cables:

https://www.dropbox.com/s/g9hjwi15zjq4k4y/Coax_Theta.jpg?raw=1

Stainless hardline is much better but it\'s expensive and hard to get.
SS barely conducts heat.

We never use Fahrenheit, except for room temp and cooking. My wife
works in degrees F.

#10 wire is 0.1\" diameter and 1 milliohm per foot. #20 is 10
mohms/foot. #30, 100 mohms. Easy to remember.



--

I yam what I yam - Popeye

 

[server]

On Sat, 19 Feb 2022 12:17:14 +0100, David Brown
<david.brown@hesbynett.no> wrote:

On 18/02/2022 23:36, Rick C wrote:
On Friday, February 18, 2022 at 1:51:04 PM UTC-5, whit3rd wrote:
On Friday, February 18, 2022 at 6:45:50 AM UTC-8,

You mean why do people use the measuring system that everyone
else in their country use? I guess this is a more pointed
question at the US community. I remember working with a
mechanical engineer at a military contractor and was surprised
they still did everything using inches. 90% of electronic
components are in mm as the primary unit. I guess I expect the
mechanical community would have converted by now, but, no.
Pre-NATO, all US military machinery would have been inches; even
now, NATO has standard 7.62 mm ammo, which is just a
soft-conversion from .30 caliber...

I would hope you\'d understand the difference in changing nomenclature
and changing measurement systems. Caliber is not an actual
measurement of anything, rather a nominal use. Same as 12 inch
wafers or a 19 inch rack cabinet. I guess something on a 19 inch
rack cabinet is actually 19 inches, but in reality, it\'s just a name
we use.


I think a key point on units is whether you need to convert them or not,
and how they are compared to different measurements. If you need to
convert things into real lengths, weights, or whatever, then metric is
the only sane choice. But often you don\'t need conversions.

It doesn\'t matter if a .44 calibre bullet is 0.44 inches wide or long,
0.44 kg in weight, or whatever - it\'s just a name, and as long as you
match up the name used on the gun and the ammo, you\'re fine.

It doesn\'t matter what width a 19\" rack is - it just matters that
everyone follows the same standard size.

The instrument front panels are 19\" wide. Any significant differences
would look goofy.

You don\'t measure the height
of the rack in centimetres - you measure it in \"units\" because
everything that goes in the rack is an integer number of \"units\" in
height. If you want to know if your new 4 unit server will fit in your
rack, you count the number of units of space you have left - conversion
to millimetres or measuring with an inchtape would be silly.

1U is 1.75 inches.

On the other side, the size of your pcb tracks and footprints, or screw
threads, or mechanical drawings, all need to be as accurate as
practically possible, and all need to be specified in a precise scale -
metric.

We do PCB layouts mostly in inches. There is no precision lost. Trace
widths measured in integer mils are convenient. \"Make that one five.\"





--

I yam what I yam - Popeye

 

[server]

On Sat, 19 Feb 2022 15:27:10 +0100, David Brown
<david.brown@hesbynett.no> wrote:

On 19/02/2022 15:15, Rick C wrote:
On Saturday, February 19, 2022 at 6:17:25 AM UTC-5, David Brown
wrote:
On 18/02/2022 23:36, Rick C wrote:
On Friday, February 18, 2022 at 1:51:04 PM UTC-5, whit3rd wrote:

On Friday, February 18, 2022 at 6:45:50 AM UTC-8,
You mean why do people use the measuring system that everyone
else in their country use? I guess this is a more pointed
question at the US community. I remember working with a
mechanical engineer at a military contractor and was
surprised they still did everything using inches. 90% of
electronic components are in mm as the primary unit. I guess
I expect the mechanical community would have converted by
now, but, no.
Pre-NATO, all US military machinery would have been inches;
even now, NATO has standard 7.62 mm ammo, which is just a
soft-conversion from .30 caliber...

I would hope you\'d understand the difference in changing
nomenclature and changing measurement systems. Caliber is not an
actual measurement of anything, rather a nominal use. Same as 12
inch wafers or a 19 inch rack cabinet. I guess something on a 19
inch rack cabinet is actually 19 inches, but in reality, it\'s
just a name we use.

I think a key point on units is whether you need to convert them or
not, and how they are compared to different measurements. If you
need to convert things into real lengths, weights, or whatever,
then metric is the only sane choice. But often you don\'t need
conversions.

It doesn\'t matter if a .44 calibre bullet is 0.44 inches wide or
long, 0.44 kg in weight, or whatever - it\'s just a name, and as
long as you match up the name used on the gun and the ammo, you\'re
fine.

It doesn\'t matter what width a 19\" rack is - it just matters that
everyone follows the same standard size. You don\'t measure the
height of the rack in centimetres - you measure it in \"units\"
because everything that goes in the rack is an integer number of
\"units\" in height. If you want to know if your new 4 unit server
will fit in your rack, you count the number of units of space you
have left - conversion to millimetres or measuring with an inchtape
would be silly.

On the other side, the size of your pcb tracks and footprints, or
screw threads, or mechanical drawings, all need to be as accurate
as practically possible, and all need to be specified in a precise
scale - metric.

That is an error. There is nothing more precise about metric than
imperial units.

I know that, and it is not actually what I said.

If everyone used imperial units consistently (which could work for
lengths, though some imperial units are different in different
countries), they could be precise.

But they don\'t - and conversions back and forth will mean inaccuracies
creep in and rounding errors can add up.

When accuracy is important, the world uses metric - except for a
decreasing proportion of hold-outs in the USA. If your drawings,
designs or measurements pass through the hands of imperial unit users in
the USA, accuracy is likely to drop.

US decimal points are just as good as metric decimal points. We can
measure inches as accurately as you can measure centimeters.

Does anybody use centimeters? Seems like an orphan unit.

The real advantage of SI units is avoiding strange conversions, like
between watts and horsepower and BTUs. Thermal calcs are a nightmare
in imperial units.

Pressure in atm is pretty arbitrary.



--

I yam what I yam - Popeye

 

[Jeroen Belleman]

On 2022-02-19 17:45, jlarkin@highlandsniptechnology.com wrote:
[...]

measure inches as accurately as you can measure centimeters.

Does anybody use centimeters? Seems like an orphan unit.

[...]

We don\'t think of centimeters as a unit. The unit is the
meter. Centi is just a prefix meaning 1/100th. Engineers
tend to use mostly prefixes that are powers of 1000.

There are some weird exceptions. You\'ll see hPa because it
happens to be close to 1mbar. You\'ll see daN because it
happens to be near the downward force of a 1kg mass.

Jeroen Belleman

 

[olaf]

jlarkin@highlandsniptechnology.com wrote:

#10 wire is 0.1\" diameter and 1 milliohm per foot. #20 is 10
mohms/foot. #30, 100 mohms. Easy to remember.

Only if you have a feeling what a \"foot\" is.

Olaf

 

[Rick C]

On Saturday, February 19, 2022 at 12:45:12 PM UTC-5, olaf wrote:

jla...@highlandsniptechnology.com wrote:

#10 wire is 0.1\" diameter and 1 milliohm per foot. #20 is 10
mohms/foot. #30, 100 mohms. Easy to remember.
Only if you have a feeling what a \"foot\" is.

That\'s easy. It\'s about how far light travels in a nanosecond. I think that was how it came about, but they didn\'t measure the speed of light very well early on. Kinda like a meter being 1 million between the equator and the poles of the Earth. Close, but not all that close.

--

Rick C.

+-- Get 1,000 miles of free Supercharging
+-- Tesla referral code - https://ts.la/richard11209

 

[Rick C]

On Saturday, February 19, 2022 at 11:45:55 AM UTC-5, jla...@highlandsniptechnology.com wrote:

Does anybody use centimeters? Seems like an orphan unit.

My skis are 180 cm. People tend to use cm for their heights. Better than hands.

--

Rick C.

+-+ Get 1,000 miles of free Supercharging
+-+ Tesla referral code - https://ts.la/richard11209

 

[whit3rd]

On Saturday, February 19, 2022 at 6:27:22 AM UTC-8, David Brown wrote:

On 19/02/2022 15:15, Rick C wrote:

There is nothing more precise about metric than
imperial units.
I know that, and it is not actually what I said.

If everyone used imperial units consistently (which could work for
lengths, though some imperial units are different in different
countries), they could be precise.

But they don\'t - and conversions back and forth will mean inaccuracies
creep in and rounding errors can add up.

Oh, that\'s a solved problem, though; sometime in the past (1935?) the US
made a three-digit conversion from \'inch\' to \'meter\' that is definitive (it
defines the inch in SI units, so Systeme Internationale applies). We here
in US have to deal with \'statute mile\' versus \'mile\' as a result, but...that\'s
not an international problem).

Conversions can be exact, but of course there\'s no getting around
numeric-representation errors; diagonal of a square isn\'t rational, so
we NEVER have \"all\" of the digits written down. That\'s not a standards
problem, it\'s just... a problem.

The \'inch\' was never international-standard; Denmark had a different inch.
That\'s why it makes little sense to make a local inch the definition of
a meter. France did the world a favor when (after a king redefined the
\'bushel\' measure to increase land rents) declared a new measure for
world distribution.

When accuracy is important, the world uses metric - except for a
decreasing proportion of hold-outs in the USA. If your drawings,
designs or measurements pass through the hands of imperial unit users in
the USA, accuracy is likely to drop.

Not just the USA; all NATO countries accept #6-32 screws as \'a\' standard size, and
BSP (British Standard Pipe) pipe threads are all over the world. Accuracy is
available equally to all, and calculators can handle more digits than I\'ve ever needed.
Cube roots to ten digits was painful before personal computing, but I could do it
with the right glowing-digits office machine. Slide rule, though, wasn\'t gonna work.

 

[Rick C]

On Saturday, February 19, 2022 at 1:48:27 PM UTC-5, whit3rd wrote:Accuracy is
> available equally to all, and calculators can handle more digits than I\'ve ever needed.

A friend was working for IBM on a military sonar problem. She had to calculate table values for a Sin lookup or something. So she used a calculator with I\'m not sure how many digits. I thought it was an HP, but that has 15 digits which would seem to be enough. The point is they had problems with the functions using this table and discovered the values were not accurate enough! I\'m surprised that even 10 digits weren\'t enough, but I guess there are issues of differences between large numbers that require very high internal accuracy in the calculations.

--

Rick C.

++- Get 1,000 miles of free Supercharging
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[John S]

On 2/19/2022 12:48 PM, whit3rd wrote:

On Saturday, February 19, 2022 at 6:27:22 AM UTC-8, David Brown wrote:
On 19/02/2022 15:15, Rick C wrote:


There is nothing more precise about metric than
imperial units.
I know that, and it is not actually what I said.

If everyone used imperial units consistently (which could work for
lengths, though some imperial units are different in different
countries), they could be precise.

But they don\'t - and conversions back and forth will mean inaccuracies
creep in and rounding errors can add up.

Oh, that\'s a solved problem, though; sometime in the past (1935?) the US
made a three-digit conversion from \'inch\' to \'meter\' that is definitive (it
defines the inch in SI units, so Systeme Internationale applies). We here
in US have to deal with \'statute mile\' versus \'mile\' as a result, but...that\'s
not an international problem).

Which \'mile\' do you mean? \'Nautical mile\' perhaps?

Conversions can be exact, but of course there\'s no getting around
numeric-representation errors; diagonal of a square isn\'t rational, so
we NEVER have \"all\" of the digits written down. That\'s not a standards
problem, it\'s just... a problem.

The \'inch\' was never international-standard; Denmark had a different inch.
That\'s why it makes little sense to make a local inch the definition of
a meter. France did the world a favor when (after a king redefined the
\'bushel\' measure to increase land rents) declared a new measure for
world distribution.

When accuracy is important, the world uses metric - except for a
decreasing proportion of hold-outs in the USA. If your drawings,
designs or measurements pass through the hands of imperial unit users in
the USA, accuracy is likely to drop.

Not just the USA; all NATO countries accept #6-32 screws as \'a\' standard size, and
BSP (British Standard Pipe) pipe threads are all over the world. Accuracy is
available equally to all, and calculators can handle more digits than I\'ve ever needed.
Cube roots to ten digits was painful before personal computing, but I could do it
with the right glowing-digits office machine. Slide rule, though, wasn\'t gonna work.

 

[whit3rd]

On Saturday, February 19, 2022 at 11:14:27 AM UTC-8, John S wrote:

On 2/19/2022 12:48 PM, whit3rd wrote:

...sometime in the past (1935?) the US
made a three-digit conversion from \'inch\' to \'meter\' that is definitive (it
defines the inch in SI units, so Systeme Internationale applies). We here
in US have to deal with \'statute mile\' versus \'mile\' as a result, but...that\'s
not an international problem).

Which \'mile\' do you mean? \'Nautical mile\' perhaps?

Land-measure miles were originally done with (I think) the convention
that 39.37 inches is exactly one meter. When the change became
official that 25.4 mm is one inch, a meter became equal to 39.370079
inches, and that would have changed all land-measure boundaries.
So, they made the land-markers correct, in a system with \'statute mile\'
instead of common \'mile\'. The \'statute foot\' is now the base for
old chains, rods, acres, etc.

units foot surveyfoot
* 0.999998
/ 1.000002