Hi Duane:
I don't know if this is the question you were actually asking, but there are
EXACTLY 25.4 mm per inch.
Cheers,
MvdW
> -Original Message-
> From: Duane Hague [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, 7 March 2001 9:42
> To: Multiple recipients of list proteledausers
> Subj
At 08:50 AM 3/7/01 +1000, [EMAIL PROTECTED] wrote:
>Point taken if it is in the decimal form but 0.1 inch is 1/10 of an inch
>and if you think of it as a fraction rather than a decimal, the fraction
>has got to be a more acurate measurment than a rounded decimal.
No, there is no difference bet
Using 2/3 of an inch or .67 of an inch, its obvious which one is the more
accurate. Maybe
fractions rather than rounded decimals used in conversions would allow better
accuracy.
___
Clive Broome
IDT Sydney Design CentrePh:
As the guilty party who triggered this digression, I feel constrained to
contribute. The change evidently occurred when I was out of the country
(military stuff) and I failed to notice it for over thirty years. My 1966
Handbook of Chemistry & Physics gives US Inch = 25.40005 millimeters and
At 12:23 PM 3/6/01 -0500, Steve Smith wrote:
>I would never assume any dimension to be dead accurate
>as you must allow for rounding off and tolerances.
This is true for measured or specified physical dimensions.
However, we should also know that 1 inch is *exactly* 2.54 cm. because that
is th
On 12:23 PM 3/6/01 -0500, Steve Smith said:
>I would never assume any dimension to be dead accurate
>as you must allow for rounding off and tolerances.
Ah...tolerances...Now why exactly would we care about those?
After all, we're in a metric age, where everything is by default exact
to the nth
Point taken if it is in the decimal form but 0.1 inch is 1/10 of an inch and if
you think
of it as a fraction rather than a decimal, the fraction has got to be a more
acurate
measurment than a rounded decimal.
___
Clive Broome
IDT S
On 09:43 AM 3/6/01 +1000, [EMAIL PROTECTED] said:
>Depends on the format of the original. 0.1inch is far more accurate than
>2.54mm
>because 0.1 = 0.10.
No. That is incorrect.
Otherwise, it would have been published as 0.10.
Though we presume it to be true, by virtue of refe
>[EMAIL PROTECTED] said:
>Depends on the format of the original. 0.1inch is far more
>accurate than 2.54mm because 0.1 = 0.10
That's not quite right.
0.1 could be anywhere between 0.050 and 0.149.
Even 0.10 could be between 0.009 and .104
I would never assume any dimension to be dead
> > Depends on the format of the original. 0.1inch is far more
> > accurate than 2.54mm
> > because 0.1 = 0.10..
> > Clive Broome
>
> By definition, 1 inch = 25.4mm exactly. This was standardised
> some decades ago.
>
> It's when rounded numbers are used that problems occur.
>
>
Depends on the format of the original. 0.1inch is far more accurate than 2.54mm
because 0.1 = 0.10..
If you go with the sequence 2.54, 1.27, 0.635 or 0.1, 0.05, 0.025 the imperial
system
is the more accurate as it has more decimal places. For high pin count devices
it
could bec
By definition, 1 inch = 25.4mm exactly. This was standardised
some decades ago.
It's when rounded numbers are used that problems occur.
Cheers,
John Haddy
> -Original Message-
> From: TSListServer [mailto:[EMAIL PROTECTED]]On
> Behalf Of [EMAIL PROTECTED]
> Sent: Tuesday, 6 March 2001
Duane,
I have also been in this situation.
Check the manufacturers data sheet.
Somewhere in the fine print should be a statement along the lines of
"Controlling dimension : inches" or "Controlling dimension : millimetres"
Of course the wording may differ between manufacturers but
0.635mm is not 0.65mm but both measurements are standard pin pitches along with
others.
If a device 'appears' to have different pin pitches it means it comes in
different
package types, so I would be double checking the manufacturers website
(eg http://www.idt.com/packages/index.html) and the s
I strongly reccomend that you get a sample part from the manufacturer and
measure it yourself. Also if their documentation is confilcting, a call
wouldn't hurt.
Mike
-Original Message-
From: TSListServer [mailto:[EMAIL PROTECTED]]On
Behalf Of Duane Hague
Sent: Saturday, March 03, 2001 3
At 04:59 PM 3/3/01 -0800, Mike Ingle wrote:
>I strongly reccomend that you get a sample part from the manufacturer and
>measure it yourself. Also if their documentation is confilcting, a call
>wouldn't hurt.
Good advice. Actually, rereading the original post, it looks like there is
only one er
Here is hoping that some knowledgeable "old hand" could point me in the
right direction. Or have I just stumbled into the rabbit hole? I am now
starting to understand the problems with footprint libraries and why "you
do your own" but am very confused about one area of detail. Any help would
At 06:57 PM 3/3/01 -0500, Duane Hague wrote:
>For example, on QFPs the same manufacturer will refer to a part as having
>a 25 "mill" (0.025 inch) pin pitch and then provide a package drawing in
>metric showing a pitch of 0.65 millimeters "Typical" (and the other
>dimensions on the drawing indic
In my experience the metric units are the more exact dimensions, with the inch
units being only a close approximation.
Found this when using a Zilog VQFP once. Board came back, and part
would only line up on pads about 3/4 way down one side of the package.
Looking closer at the mechanical dat
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