General > General Technical Chat
why is the US not Metric
VK3DRB:
--- Quote from: jonovid on October 25, 2019, 10:24:21 am ---here in Australia everything is Metric, like most of the world.
--- End quote ---
WRONG.
Most engineers in Australia, including me, still use the term "0402", "0603", "0805" etc for surface mount resistor sized. There is some crossover in name sizes between imperial and metric which just adds confusion. But I can live with this.
But what is really annoying is engineers in Australia who use an imperial grid for schematic symbol grid lines in Altium. So when my schematic symbols have a 2.50mm grid pattern and I have to use them to modify some imperialist's 0.1" grid, the bloody pins don't line up.
Australians should abandon the antiquated imperial measurements once and for all. And use kPa rather that PSI.
I think the only countries that have not moved to metric are Liberia, Burma and, you guessed it... the USA :scared:
vad:
--- Quote from: Monkeh on October 26, 2019, 02:05:06 am ---
--- Quote from: vad on October 26, 2019, 12:59:58 am ---No, it does not. 10 AWG would be sufficient for 10A for residential wiring.
10 AWG copper wire has resistance of 0.9989 Ohm per 1000 feet at room temperature. 10A through 75-feet long circuit branch gives 1.5V voltage drop both ways, which is acceptable.
--- End quote ---
And 10AWG is ridiculous for a 120W circuit! Nor is >10% drop acceptable by any reasonable standard. How on earth is this better than putting a 12V supply at the point of load, as you can already do? It's more expensive, harder to work with, and less efficient!
--- End quote ---
10% power loss in the worst case scenario (the maximum distance from distribution box) is far better than typical SMPS losses at the point of load.
Yes, it would be more expensive. Let me guess... Wiring 10 low-voltage branches for lighting receptacles would be $200-300 more expensive in material costs than wiring ten 14AWG lighting branches. That’s a whooping $10 per year, when amortized over 27.5 years period. Jeez...
vad:
--- Quote from: VK3DRB on October 26, 2019, 02:14:27 am ---
--- Quote from: jonovid on October 25, 2019, 10:24:21 am ---here in Australia everything is Metric, like most of the world.
--- End quote ---
WRONG.
Most engineers in Australia, including me, still use the term "0402", "0603", "0805" etc for surface mount resistor sized. There is some crossover in name sizes between imperial and metric which just adds confusion. But I can live with this.
But what is really annoying is engineers in Australia who use an imperial grid for schematic symbol grid lines in Altium. So when my schematic symbols have a 2.50mm grid pattern and I have to use them to modify some imperialist's 0.1" grid, the bloody pins don't line up.
Australians should abandon the antiquated imperial measurements once and for all. And use kPa rather that PSI.
I think the only countries that have not moved to metric are Liberia, Burma and, you guessed it... the USA :scared:
--- End quote ---
At least we drive on the right side of the road, unlike people of Botswana and Bangladesh.
Monkeh:
--- Quote from: vad on October 26, 2019, 02:52:16 am ---
--- Quote from: Monkeh on October 26, 2019, 02:05:06 am ---
--- Quote from: vad on October 26, 2019, 12:59:58 am ---No, it does not. 10 AWG would be sufficient for 10A for residential wiring.
10 AWG copper wire has resistance of 0.9989 Ohm per 1000 feet at room temperature. 10A through 75-feet long circuit branch gives 1.5V voltage drop both ways, which is acceptable.
--- End quote ---
And 10AWG is ridiculous for a 120W circuit! Nor is >10% drop acceptable by any reasonable standard. How on earth is this better than putting a 12V supply at the point of load, as you can already do? It's more expensive, harder to work with, and less efficient!
--- End quote ---
10% power loss in the worst case scenario (the maximum distance from distribution box) is far better than typical SMPS losses at the point of load.
--- End quote ---
And yet you've still got those losses back at the point of distribution - only a little lower in practice, with much higher transmission losses to account for.
--- Quote ---Yes, it would be more expensive. Let me guess... Wiring 10 low-voltage branches for lighting receptacles would be $200-300 more expensive in material costs than wiring ten 14AWG lighting branches. That’s a whooping $10 per year, when amortized over 27.5 years period. Jeez...
--- End quote ---
And it's not going to save you $10 a year, and is going to waste materials which didn't have to be used. 14AWG x 10 circuits is already a stupid waste.
Rick Law:
--- Quote from: German_EE on October 25, 2019, 06:46:04 pm ---Years ago I remember being told that the reason the USA hadn't converted to metric was the cost of retooling, imagine the cost of replacing all those lathes and milling machines, plus the drill bits and everything else.
However............................
Lots of US companies now have their stuff made in Asia, who are quite comfortable working with either system, and the cost of conversion has now shrunk.
--- End quote ---
re: "Years ago I remember being told that the reason the USA hadn't converted to metric was the cost of retooling..."
I remember the same. Pride or familiarity was not the main topic of discussion, but the cost vs benefit of having the same units. The fight was between the importers, exporters, manufacturers, so on. Manufacturers will be the ones particularly hard-hit in the change because their manufacturing machinery is expensive.
One must also consider, metric is as abstract as any other measurement and there is no intrinsic advantage in using it other than international trade. Manufacturers/suppliers now adopted a different route to internationalization - with their own units that is even more abstract. Now a "size 10" shirt from one manufacturer isn't the same size as a "size 10" from another. Heck, it is not even the same "size 10" a year later from the same manufacturer.
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