Must start thinking in metric!!
Oldbitcollector (Jeff)
Posts: 8,091
Like many American students growing up in the 70s and 80s, I was taught how to do size estimation in school using the Imperial standards of inches, feet, quarts, gallons, etc, etc.
Now that I'm designing products and becoming a member of the "world community", I'm finding that my favored measuring increment of the "inch" is like talking Greek. (Greece also uses the metric system, so I guess that example really doesn't work either.)
Designing products for add-on products hasn't helped either. While Parallax is clever enough to post the "cm" sizes of their product, you can tell they went to the same schools I did growing up. For example, the Quickstart dimensions are 2" x 3" (5.1 cm x 7.6 cm) . Yeah, we know that no one would design anything .1
So gang, it's probably time for the American community to follow the world's lead, swallow hard and then learn to start calculating, (and thinking!) in metric measurements. Hey Parallax & other Parallax designers come along for the ride. It'll make creating supporting products that much easier.
I have found a few useful resources in helping some of us old dogs learn metrics.
http://thinkmetric.org.uk/ (Notice the .uk top level domain? heh)
http://www.learner.org/interactives/metric/metric.html
Sorry about the mile kilometer long post, but I thought it might be a worthy discussion since there are a few other PCB designers here. It'll take me some time to get my head to quit calculating in inches, Until them, I'll be using Google's conversion calculators a lot more this year.
Jeff
Now that I'm designing products and becoming a member of the "world community", I'm finding that my favored measuring increment of the "inch" is like talking Greek. (Greece also uses the metric system, so I guess that example really doesn't work either.)
Designing products for add-on products hasn't helped either. While Parallax is clever enough to post the "cm" sizes of their product, you can tell they went to the same schools I did growing up. For example, the Quickstart dimensions are 2" x 3" (5.1 cm x 7.6 cm) . Yeah, we know that no one would design anything .1
So gang, it's probably time for the American community to follow the world's lead, swallow hard and then learn to start calculating, (and thinking!) in metric measurements. Hey Parallax & other Parallax designers come along for the ride. It'll make creating supporting products that much easier.
I have found a few useful resources in helping some of us old dogs learn metrics.
http://thinkmetric.org.uk/ (Notice the .uk top level domain? heh)
http://www.learner.org/interactives/metric/metric.html
Sorry about the mile kilometer long post, but I thought it might be a worthy discussion since there are a few other PCB designers here. It'll take me some time to get my head to quit calculating in inches, Until them, I'll be using Google's conversion calculators a lot more this year.
Jeff
Comments
I agree this remains a big problem and we have to solve it. When we ship any electro-mechanical product to Europe we inconvenience those customers the second they need to replace a screw, bolt, or whatever. PCB metric dimensions are not a problem, but it's all the parts around the PCB if they are of mechanical nature.
We are losing some of the Euro market by not providing metric. I realize this is a reality.
It's just too bad we Americans didn't dump the English system at the same time we gave King George the boot.
You guys obviously have wonderful American sources for hardware. Last week when my China supplier of 10mm standoffs shipped in power connectors instead, I started looking for a quick source here in the states for the part I needed. Not only did the same part cost 10x as much, but the real issue was the 6 week delay before I could get them. (I'm guessing their China fabrication facility takes a little longer than my source to fill their orders. !!)
Jeff
One interesting detail about Chinese-manufactured screws, standoffs and spacers in imperial sizes is that they are not stocked in China anywhere. They build to order for anything of imperial sizes. We have never had success with imperial standoffs and screws, nuts in China. I'm willing to bet that they even manufacture on-the-spot the 10mm standoffs you ordered. If there's such thing as a lean production environment, that's China. Restaurant or factory - they go from raw materials to finished goods in a single-line transformation.
Except you weren't, not exactly. An Imperial Pint is much bigger than the puny American version, which is very important when it comes to beer. As a consequence all your gallons and quarts etc are wrong as well. Which really messes up any comparison of fuel consumption in miles per gallon between the nations.
Now, we really don't want beer in metric because we then get served 500ml which is miserably short of a pint.
Strangely enough in recent years cans of beer have started appearing in stores around Scandinavia that are full size Imperial pints instead of puny 500ml. Naturally this idea has caught on well:) Stupid Brits are still exporting special Euro market 500ml bottles here.
Ah yes, electronics, of course those one tenth inch spacings on headers an DIP chips is perfect. Go metric and we will soon need microscopes to build anything.
However, my pet peeve unit of measurement is the gauge. What is a gauge? It seems to morph based upon the material (e.g. wire, plastic, screws, sheet metal, shotguns). I'm probably missing some big picture thing because it seems completely arbitrary.
But change isn't easy. A few years ago I bought a new bicycle odometer and figured I'd try to force myself into using the metric system by configuring it to read kilometers instead of miles, but never became comfortable with it, and eventually changed it over to my familiar old mile units.
Max Planck said this about new scientific ideas, but I wouldn't be surprised if it was true also about use of units:
"A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new
generation grows up that is familiar with it."
So maybe instead of trying to force ourselves too hard, we should focus instead on raising our children to use metric.
The answer to your beer problem is to insist on being served by the liter.
As for the US making the switch, while it would be a lot of work initially it would pay big dividends for the economy and manufacturing efficiency in the long run. Just switching to standard metric fasteners could reduce the number of inventory items to stock by as much as 60%. For the electrical and electronics industry it could be even more significant.
And if wire size was in millimeters instead of gauge calculating the size of conductor for a specific current would be trivial.
So in order to advance science, we MUST die.....that sure would make me consider a business major if I was a kid!!
I'm starting to adjust to metric for the really small stuff. For example, I know implicitly that an IC with a 0.65 mm lead pitch will be harder to solder than one with a 0.05" pitch. But anything bigger than about 25 mm I have to convert to approximate inches to visualize: multiply mm by 4 and divide by 100. But for PCB layout, I'm constantly shifting back-and-forth between metric and English in my CAD system (thankfully made easy just by hitting the "U" key, then selecting a different grid snap). IC pad patterns are more often spec'd in mm now than inches, but part placement snaps and design rules are still dominated by inches.
-Phil
Just consider yourself lucky. In Taiwan, we actually have traditional Chinese weights and measures used in some situations.
You can't buy a pound or a kilo of bananas, you have to buy a jin or a half jin. Autos in Taiwan are both in metric and imperial -- depending on their origin. And all my bank statements for this year are dated 101 as the years are officially base on the founding of the Republic of China by Sun Yat Tsen.
Nonetheless, I have gotten used to watching the weather in centigrade and wind speed of typhoons in km per hour.
And my lattes at Starbucks are not measured in ml, they are in cc. But that is rather trivial.
Needless to say, it is more difficult than you would think to change from those clunky American units to the international standard.
Japan has liter beer bottles and cans.
The metric system is great, this is the only example that need to be cited.
Anybody that does not like the metric system, get them a 6 pack and they will change their mind, or at least forget what you were talking about.
not sure about Fahrenheit but the definition of celsius comes from water. 0C is when water freezes and 100C is when water boils. I remember something like 100F is the normal human temperature ...
Anyways Celsius is additive, just one degree celsius is different from one degree Fahrenheit...
So coming from Germany (metric) to the US of is quite a challenge. Lets say nuts and bolts, or drills. Easy. if 8mm is to small try 9mm. But here? 7/56 , 1/8, ? WTF? Why, If you buy some wood, is a 2 by 4 actually 1.95 by 3.75? Another example. I ned some brick-tiles for my driveway. in metric it would be mesured in square meters. Here an MendoMills they ask me - how many YARDS? I feel helpless sometimes...
Enjoy!
Mike
My view is to ignore unneeded standards shoved down our throats by others.
Gauge is weird, yes...
From what I understand, a 12gauge shotgun is called so because if you take a lump of lead of a certain weight, and cast it all into round balls, you get exactly 12 of the size that would fit in that barrel.
Wire and sheet I guess works somewhat the same, except that on sheets, you take a lump of metal, then pile said number of african elephants on top. The larger number of elephants, the thinner the sheet...
To help people adjust to Metric...
At 0 degrees Celsius, water freezes to ice or melts... At 100 degrees it boils(assuming sealevel air pressure of 1000millibar)
In Norway, if you ask for a half liter of mead... you get a paltry .4L in most bars...
1Kg is pretty close to 2.2lbs to not make much of a difference.
1Mile is 10Km, or if it's an Imperial mile, its 1.609Km.
(you're not too far out of the ballpark if you just multiply/divide by 1.5)
Unless you're playing around with Nautical miles, which happens to be 1853meters.
( 1Nautical mile also happens to be 10 'international cables')
But must not be confused with the sea mile, tactical or data mile...
Computer circiuits are weird as for one reason or another, we're using decimal inches...
Maybe 1/16" was a too narrow gap between pins when the first modern ICs appeared?
On my bicycle I have 1.75" tires on my 26" rims.
On my car I have 185-75/14, I think...
My Lubitel (uses 6x6cm negatives) camera has a 75mm lens.
Which takes pictures with the same angles as my Olympus OM 10 with a 50mm lens...
On any digital, a 50 or 75mm would be a telephoto lens, but on the Lubitel and OM 10 they're 'Normal' lenses.
11mm on my digital would be a 'normal' but the same size is a fisheye lens on my OM 10...
The 28mm in my Zenit Horizon(120degree panoramic) is physically too small for my OM 10(even if the camera bbodies are similarly sized and uses the same film) but could probably be used as a telephoto on my cell-phone...
Why the H! do we measure the lens this way anyway?
Wouldn't the arc be better?
Heading off to crawl into my 90cm wide bed...
(not 3' or a yard, 90cm exactly)
You're scaring me. Aren't ml and cc the same thing? If not, I'm in trouble.
A lens will have another spec (the "format") that tells how big of an image it can form on the focal plane before it cuts off at the edges or vignettes. This relates as much to the physical size of the lens as to the focal length. Obviously, a lens of a given focal length designed to form an image on 8" x 10" film has to be bigger than one used with a 1/3" CMOS sensor.
The field-of-view, measured in degrees, is a property that combines both the lens focal length and the physical dimensions of the sensor/film's focal plane. The smaller the sensor for a given focal-length lens, the smaller the field of view and the more the lens appears to be a telephoto.
-Phil
I agree with most of this, but it sure is easier to count by .1 inch than it is 2.54 mm - tongue in cheek
Japan actually has two separate electrical power grids. One is a 50 cycle metric power grid that was built before WWII with the help of the Germans (or Prussians) - that's metric and in the eastern side of the main island that wasn't destroyed in the war. The other power grid was built with the help of the USA after WWII and that is 60 cycle power.
Even if the USA were to change everything else to metric, it would be slow to convert the power grid from 60 cycle to 50 cycle. The cost would be far to great.
Long tons, short tons, and metric tons. Pounds, shilling, pense. 4 bits to a quarter, 8 bits to a half dollar. There was a time when everything required a conversion. Lumber is sold by the board foot, which is actually 1/12th of a cubic foot.
-Phil
-Phil
Guess how many industrialized nations have not adopted S.I. as the official system of measurement?