That state of metric conversion in the US

Feb 16, 2013 327 Replies

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Germans have vanity plates now? I was there late last year, never saw any.

That happens a lot out here. Sometimes big stuff flies around on the highways, such as fireplace logs. Had one bang through underneath my car, luckily it has sturdy skid plates.

Regards, Joerg http://www.analogconsultants.com/

still

easy

much.

No argument there. Device package outlines and such used to be tied to the US inch. Now most package outlines and pin/contact spacing is basically metric, with translations to imperial.

OTOH these changes have made hash out of correctly reading old surveying data which is minimum 5 and usually 6 or more places accurate. I have some surveyor friends. It is actually a lot worse than that, ask a surveyor though, i do NOT know enough to answer those questions.

?-)

"Dumbass"? Again??? You're really not very good at this, are you?

Nico Coesel schrieb:

Hello,

it is not very nice to manually rout a PCB when you got a mix of parts with different pin distancesbased on inch and mm, for instance 100 mils and 2 mm.

Bye

when free trade started and US goods appeared cheaper as did any food by th e pound rather than kg or 2.2lb.

onversant in millimeters and km

compared to 'C.

ting to metric for Americans, so they shall be in their archaic units of me asure for a long time.

How is C any more linear than F?

I blame that socialist Obama!

free trade started and US goods appeared cheaper as did any food by the pound rather than kg or 2.2lb.

conversant in millimeters and km

compared to 'C.

to metric for Americans, so they shall be in their archaic units of measure for a long time.

ObTrivia:-

The original scale that Fahrenheit used was based on three fixed points, and in fact was only piecewise linear. Of course that's not the scale which now bears his name.

I thought he was a muslim? Can muslims be socialist too?

John Devereux

when free trade started and US goods appeared cheaper as did any food by the pound rather than kg or 2.2lb.

conversant in millimeters and km

compared to 'C.

converting to metric for Americans, so they shall be in their archaic units of measure for a long time.

Isn't the Kelvin scale based on a number of fixed points?

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John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

No, *STILL*, dumbass. You insist on proving it with every post.

No, I'm not a perfect dumbass, like you. That's obvious.

That certainly depends on the package. There are *many* packages that are still inch based, particularly connectors. ...unless you're saying that since the inch is based on the meter, packages that are based on inch measures are metric.

PCB packages are happy with either system.

Every board I've done in the last 20 years has had a mix. I don't see that changing, at least in my lifetime. ".100 (and less so, .050") spacing connectors will be with us forever. I don't see it as an issue, though. PCB layout software is quite happy working in both systems.

108 mils, 100 mils, 50 mils, 20 mils, 2 mm, 1 mm, 0.8 mm... the list is endless.
John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

Last time I checked, a pint was *exactly* 16 fluid ounces regardless of what was in it.

Rick

My grand mother was a good cook. Her way of measuring content of salt, sugar etc., was a dash of this and a dash of that!

I wonder if the metric system has a replacement for that! :)

Jamie

In my first college chem lab session I was told that a drop of water was 1/10 ml.

But not 16 ounces (avoirdupois).

You have totally lost me on this one. Who was talking about 9/64ths? The original point was that it may not be hard to turn fractions into other types of numbers, but converting other measurements into fractional inches is a PITA. The questions was, what is 4 mm in fractional inches. I don't get why 10/64ths would be given in place of

5/32. I don't think I even have a measuring device that is marked in 64ths of an inch other than possibly a 6" steel rule that I don't even know the whereabouts of at the moment.

My point was that metric is just a better way to go, in part because all the measurements are decimal which is just so much easier to work with in nearly all situations.

Rick

If you are in the US you must be the only one! Every once in a while I see someone from outside the US in a PCB layout forum talk about board dimensions in metric and I have to do all the conversions myself. No one else in these groups uses metric for layer/board thickness or trace widths. The layout package I use can't even be set for metric trace widths in spite of the fact that in the data files *all* dimensions are in nanometers to make conversions easy (its easy to go from inches to metric exactly, but not the other way so much). Some foreign vendors expect metric dimensions and give metric design rules. One thing that always bugs me is when I do a metric based layout and get design rule errors because something is 9.84... mil instead of 10 mil. Or I have even seen design rule checking tools barf on 9.999... which turns out to be round off error in the durn tool!

On my next design I plan to do all the work and documentation in metric.

Rick

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