Imperial is already peculiar but when the "decimals" are not pico, nano, milli, kilo, mega etc. things become more complicated. I did never hear of "thou" before except that it is the same as "you".
That being said, the "thumb" (=inch) is still being used here to the dismay of many. "Give me that 3 quarters of a thumb valve please". Eh ?!?!?
That being said, the "thumb" (=inch) is still being used here to the dismay of many. "Give me that 3 quarters of a thumb valve please". Eh ?!?!?
Body part lengths have been used from pre-history. Fathoms, yards, feet and inches being four that spring to mind.
Fathom = height of a tallish man
Yard = tip of outstretched finger to nose
Foot = length of a (male) foot
Inch = length of a thumb
None of these would be standardised until much later.
At some time around the 18th century there was much activity to use the circumference of the Earth as a measure. It ended up as 40Gm = one circumference and that became the start of the SI (Systeme International) measurement standard. and still used by scientists on the cgs unit nomenclature.
I think mks came a little bit later and this is the current "metric" measurement standard. At least in the UK we tend to separate SI from metric in this cgs vs mks fashion. Our UK schools still erroneously teach cgs and refer to it as metric. Unfortunately that has to be untaught, when entering industry that uses the mks version of metric.
Fathom = height of a tallish man
Yard = tip of outstretched finger to nose
Foot = length of a (male) foot
Inch = length of a thumb
None of these would be standardised until much later.
At some time around the 18th century there was much activity to use the circumference of the Earth as a measure. It ended up as 40Gm = one circumference and that became the start of the SI (Systeme International) measurement standard. and still used by scientists on the cgs unit nomenclature.
I think mks came a little bit later and this is the current "metric" measurement standard. At least in the UK we tend to separate SI from metric in this cgs vs mks fashion. Our UK schools still erroneously teach cgs and refer to it as metric. Unfortunately that has to be untaught, when entering industry that uses the mks version of metric.
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OT
Remembering primary school (6th year) way back .
Our teacher told us students the length of an inch.
- Every lesson I'm going to randomly ask one of you how long an inch are.
The teacher first asked one who knew. The following answers served as repetition and soon everyone knew.
Btw, car tires (or tyres) is an perfect example of total unit mixup. Diameter in inch, width in mm and profile as percentage of width.
/OT
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the run flat tyres uses a metric rim diameter. I think this was deliberate to avoid the wrong tyre type being fitted.
One oddity of radial tyre sizing is the 10mm increments of width, yet all the withs have 5mm for the last digit.
Crossply tyres are nearly always sized in inches or decimal parts thereof.
One oddity of radial tyre sizing is the 10mm increments of width, yet all the withs have 5mm for the last digit.
Crossply tyres are nearly always sized in inches or decimal parts thereof.
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UK school kids have been taught to be metric since the 70s. all their parents have been taught metric.
Here we have two (and maybe three) generations that should know nothing about the old imperial measures and yet kids in general think in inches.
It can only be the grandparent influence, or is the "natural" thumb measurement reference still strong?
Poll?
which is the stronger influence for UK school kids still using inches? Grandparents, or thumbs?
Here we have two (and maybe three) generations that should know nothing about the old imperial measures and yet kids in general think in inches.
It can only be the grandparent influence, or is the "natural" thumb measurement reference still strong?
Poll?
which is the stronger influence for UK school kids still using inches? Grandparents, or thumbs?
Piping for water or gas come in thumb and millimeter here, no confusion possible, much safer. Why bicycle tubes and tires are still in inches is beyond me.
A nautical mile is 1/60th of a geographical degree (second/minute), 1852 meter.
Which makes it much easier to work with than (kilo)meters.
A nautical mile is 1/60th of a geographical degree (second/minute), 1852 meter.
Which makes it much easier to work with than (kilo)meters.
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Every kid in those days knew that an ounce was 28 grams. Except in New York, where it was 25.
At the equator.
meter is an instrument for measuring
(kilo)meter is an instrument for measuring kilos
metre is r before e
kilometre is also r before e
North Americans would spell metre incorrectly as meter.
They also spell tyre incorrectly as tire.
You are doing both.
Are you from North America, even though you sport the Netherlands flag and state Rotterdam as one of your locations?
As with a whole lot of other things Americans have been infected with, it's also meter/kilometer in Dutch.
Plus Afrikaans, in Germany, Scandinavian countries, several Eastern European nations.
Some words are tricky to keep apart when writing.
It's easier if the spelling is completely different (or contains a single different letter, as e.g. kilometre in Spanish/Papiamentu)
Easiest of course is for individuals who master a single language only, such as you.
(I've lived in both, majority of my family members have the US citizenship)
Plus Afrikaans, in Germany, Scandinavian countries, several Eastern European nations.
Some words are tricky to keep apart when writing.
It's easier if the spelling is completely different (or contains a single different letter, as e.g. kilometre in Spanish/Papiamentu)
Easiest of course is for individuals who master a single language only, such as you.
(I've lived in both, majority of my family members have the US citizenship)
No one has mentioned the screwed up measurements of volume; ounce, pint, quart, and gallons. How many ozs in a gallon?, you have to do some thinking or math unless you just remember all of that stuff. The metric system is SOOOOOO much easier. NO damn fractions either. Tools are so much simpler in metric, what socket is between 5/16" and 1/4"? Compare that with what socket is between 12mm and 10 mm? 80s ish and later American cars are screwed up also, my '86 Corvette is all metric EXCEPT the engine!
Craig
Craig
In Swedish it's "tum." As in "Jag har en 12-tums penis." (as heard in the movie 'Splash')
But since 1959, after innumerable incompatibility troubles among the Allied countries, using at least three differently defined 'inches' during WW2, the inch is now also a metric unit, ie defined to be exactly 25.4mm.
Two more data points
OK, I had some time I had to be down in the shop, so did the mica and the nuthin tests.
Same heatsink, same FETS, same power (25W per TO-220 device). Same heatsink temperature (or pretty close anyway).
I had to run the 'nuthin' test twice, as I was seeing one FET about 7 degrees higher than the other. Apparently some crud had gotten under the part when I took the alumina insulator out (?). I hadn't cleaned, just smoothed and added a little goop first time. Whatever, I cleaned off the FETs and the heatsink, put new goop on the FETs and did it again.
One of the interfaces done with the premium nuthin measured 0.16C/W, the other was 0.144C/W. Average 0.152C/W.
With new mica insulators, one was 0.53C/W, the other was 0.71C/W. average is 0.62C/W. The difference between the two seemed like a lot, so I checked under the parts and insulators, all looked clean. Then I wiped off the insulators and measured the thickness of each (using an ancient micrometer that was my grandfather's). Unfortunately I lost track of which was which, but one measured 2.0mil (51um), the other 2.5mil(63um). Not a huge difference, and I don't know whether the thicker one was on the FET which had the higher temp, though the ratios aren't too far apart.
The results are a lot more in favor of the aluminas than I would have thought. The tests were done on different days, though, tightening of screws might not have been the same (I don't have a torque wrench, and was going by when I saw deflection on the long allen wrench I use on the caphead screws). There might have been differences with the contact of the thermocouple, that was hard to get stable both days.
So, if taken at face value, what's it mean? Well, if your parts are getting close to their max (125C for most devices, 175C for some MOSFETS), then do whatever you can, alumina, nuthin, or BeO if you happen to have a stash put away ...and don't expect the amp to be passed down as an heirloom to your decendents. If you have margin, then expected semiconductor life is said to double with every 20C decrease in junction temperature. If the thin alumina insulators are indeed 0.43C/W better than mica, then you'd have to be dissipating 46.5W in the TO-220 device to double the part's life by switching to alumina. I'm dissipating about half that, 25W, so I gain 10.7C with alumina, or about 45% more expected life. This is all assuming failure was not caused by other things, and that the semiconductor heat/age is what will be making the amp eventually die. I'll be operating the junction 95C below its max allowed (84C below if with mica), so the FETS should live long and prosper . But since I got the thin alumina insulators, I'll use them of course. Anything worth doing is worth overdoing, right?
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OK, I had some time I had to be down in the shop, so did the mica and the nuthin tests.
Same heatsink, same FETS, same power (25W per TO-220 device). Same heatsink temperature (or pretty close anyway).
I had to run the 'nuthin' test twice, as I was seeing one FET about 7 degrees higher than the other. Apparently some crud had gotten under the part when I took the alumina insulator out (?). I hadn't cleaned, just smoothed and added a little goop first time. Whatever, I cleaned off the FETs and the heatsink, put new goop on the FETs and did it again.
One of the interfaces done with the premium nuthin measured 0.16C/W, the other was 0.144C/W. Average 0.152C/W.
With new mica insulators, one was 0.53C/W, the other was 0.71C/W. average is 0.62C/W. The difference between the two seemed like a lot, so I checked under the parts and insulators, all looked clean. Then I wiped off the insulators and measured the thickness of each (using an ancient micrometer that was my grandfather's). Unfortunately I lost track of which was which, but one measured 2.0mil (51um), the other 2.5mil(63um). Not a huge difference, and I don't know whether the thicker one was on the FET which had the higher temp, though the ratios aren't too far apart.
The results are a lot more in favor of the aluminas than I would have thought. The tests were done on different days, though, tightening of screws might not have been the same (I don't have a torque wrench, and was going by when I saw deflection on the long allen wrench I use on the caphead screws). There might have been differences with the contact of the thermocouple, that was hard to get stable both days.
So, if taken at face value, what's it mean? Well, if your parts are getting close to their max (125C for most devices, 175C for some MOSFETS), then do whatever you can, alumina, nuthin, or BeO if you happen to have a stash put away ...and don't expect the amp to be passed down as an heirloom to your decendents. If you have margin, then expected semiconductor life is said to double with every 20C decrease in junction temperature. If the thin alumina insulators are indeed 0.43C/W better than mica, then you'd have to be dissipating 46.5W in the TO-220 device to double the part's life by switching to alumina. I'm dissipating about half that, 25W, so I gain 10.7C with alumina, or about 45% more expected life. This is all assuming failure was not caused by other things, and that the semiconductor heat/age is what will be making the amp eventually die. I'll be operating the junction 95C below its max allowed (84C below if with mica), so the FETS should live long and prosper . But since I got the thin alumina insulators, I'll use them of course. Anything worth doing is worth overdoing, right?
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Thank you for the tests, the difference is more than I expected. Acording to this test, another good thing about almina would be less C/W diversity between them compare to mica, probably due to flatter surface and/or the same thickness.
BTW, does anyone have an idea if any big difference between different type of GOOPs, such as Arctic Silver and regular white one?
BTW, does anyone have an idea if any big difference between different type of GOOPs, such as Arctic Silver and regular white one?
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