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'[OT] newbie question on timing'
2005\11\30@223656 by R. I. Nelson

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This has to be a different meaning in different country thing.  I n all
school, college and military classes I have taken the word EXACT  means
right on no variance one way or the other.  To my knowledge engineering
is supposed to be an "exact science". Not a half way thing of "that
looks close enough".

for an example here is the reason  this is "ABOUT" and not "EXACTLY"

The error factor is .18 per HR. 4.32 per day,  30.24 per week.
Thats about and not exactly in my line of  thinking.

I do not have  to be that exact.  The only reason I am writing this  is  
clarify the difference between about and exact.


Russell McMahon wrote:

>>> 55ms (or 55.55555ms to be more exact)  is about 18 pulses per second.
>>
>> If you want 55.55555 ms, that's *exactly* 18 pulses/second.
>
>
> In engineering at least, 'about' includes 'exactly' :-)
>
>                RM



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2005\11\30@230623 by Anand Dhuru

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>  To my knowledge engineering
> is supposed to be an "exact science". Not a half way thing of "that
> looks close enough".
>

Mr. Heisenberg would not agree with that, would he?

Regards,

Anand


'[OT] newbie question on timing'
2005\12\01@063854 by Gerhard Fiedler
picon face
R. I. Nelson wrote:

> This has to be a different meaning in different country thing.  I n all
> school, college and military classes I have taken the word EXACT  means
> right on no variance one way or the other.  To my knowledge engineering
> is supposed to be an "exact science". Not a half way thing of "that
> looks close enough".

Mathematics (and logic) is the only thing that's exact, and it's neither
science nor engineering. I'd go so far as to say that there's /nothing/
exact in engineering (and that goes for every country I know :). Every
measurement has a tolerance range around it, and not even that range is
exact, as it's usually just a short hand notation for a not quite well
known probability distribution around the given value.

In science and engineering classes, IMO, should be taught that e.g. 6 V
doesn't really say much, it needs to be e.g. (6 +-0.2) V to make sense.
Because for example (6 +-0.00001) V is something quite different -- and
even that's pretty close to "right on" or "exact" or "no variance", it's
obviously none of these. I've never seen a measurement that was 6 V
/exact/, in the sense of (6 +-0) V. And, you may find that ironic (but it's
actually quite obvious), the more you get into high precision work, the
more important become the tolerances. They are left out (and as such are
implied to be low precision) only in low precision situations; everywhere
precision is relevant they always use values with tolerances.

I don't know whether you have done engineering work for other people. One
of the most common phrases one hears is "that's close enough" (or maybe
"that's too expensive, make it simpler" :). We (almost) never do the best
we could do given unlimited funds and time, we pretty much always do it
"good enough" and "as simple/cheap/quick as possible". Nothing "exact" or
"precise", all a matter of trade-offs, a lot of "half way things". Having a
good feeling for the "right" trade-off is basically what engineering is
about... :)

Now I don't know much about the military. Maybe they operate in a different
universe :)

Gerhard

2005\12\01@072518 by olin piclist

face picon face
R. I. Nelson wrote:
> To my knowledge engineering is supposed to be an "exact science".

Not quite, but close enough I guess.

******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\01@132955 by R. I. Nelson

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I have worked in a machine shop that was climate controlled Temp and
humidity. if the climate went out of the control zone we would have to
stop operations on some materials.

I know on the less critical stuff that I worked on we had Tolerances on
every drawing   most of the stuff I did was + or - 0.0005".  but we
still tried and usually achieved 0 tolerance.  our measuring tools were
checked daily and we had gauge blocks to double check them.

That is why I say 18 pulses per second is ABOUT 55.55555ms. and not EXACT.


Gerhard Fiedler wrote:

{Quote hidden}


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2005\12\01@144526 by olin piclist

face picon face
R. I. Nelson wrote:
> most of the stuff I did was + or - 0.0005".  but we
> still tried and usually achieved 0 tolerance.

Clearly not.  Saying stuff like this that obviously can't be true just
eliminates your credibility.  Even if your tools told you the error was 0,
that means it was only as close as the tool's accuracy and your ability to
read it.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\01@151157 by Paul Hutchinson

picon face
> -----Original Message-----
> From: piclist-bouncesspamKILLspammit.edu On Behalf Of R. I. Nelson
> Sent: Thursday, December 01, 2005 1:28 PM
>
<snip>
> every drawing   most of the stuff I did was + or - 0.0005".  but we
> still tried and usually achieved 0 tolerance.  our measuring tools were
> checked daily and we had gauge blocks to double check them.

To be correct you should say that you could not measure the deviations with
the equipment you used. No measuring instrument or gauge block has zero
error. Even the NIST Length Scale Interferometer has an uncertainty in it's
measurement, it is incredibly small but there.

Paul

2005\12\01@151431 by David Van Horn

picon face
> R. I. Nelson wrote:
> > most of the stuff I did was + or - 0.0005".  but we
> > still tried and usually achieved 0 tolerance.
>
> Clearly not.  Saying stuff like this that obviously can't be true just
> eliminates your credibility.  Even if your tools told you the error
was 0,
> that means it was only as close as the tool's accuracy and your
ability to
> read it.

Well now.. He did only express a single digit of precision on the
tolerance.
Perhaps the final measurement was done with a yardstick.  

:)



2005\12\01@155735 by Steph Smith

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face
In engineering exact means 'as close as possible',that means taking account
of tolerances
in the manufacturing process.somewhere inbetween plus and minus tolerance
ranges lies 'EXACT' which is a theoretical figure.Hence the statement in
'about' lies 'exactly'.
{Original Message removed}

2005\12\01@164346 by R. I. Nelson

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Olin Lathrop wrote:

> R. I. Nelson wrote:
>
>> most of the stuff I did was + or - 0.0005".  but we
>> still tried and usually achieved 0 tolerance.
>
>
> Clearly not.  Saying stuff like this that obviously can't be true just
> eliminates your credibility.  

I think your credability has just been put in question with your above
statement. www.mytoolstore.com/starrett/micro009.html.
This one gives readings of  0.0001

> Even if your tools told you the error was 0,
> that means it was only as close as the tool's accuracy and your
> ability to
> read it.

using a magnifier attached to glasses to better read the scale  And a
precision gage block that has been precision ground to check calibration.

There are micrometers available  that have a resolution of 0.00002" and
accuracy of 0.000015"

I can send alink to that if you are interested.





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2005\12\01@165029 by Gerhard Fiedler

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Olin Lathrop wrote:

>> but we still tried and usually achieved 0 tolerance.
>
> Saying stuff like this that obviously can't be true just eliminates your
> credibility.  

How could I miss that... the other discipline (besides mathematics) that
deals with "0 tolerance" is politics. But there is this credibility dilemma
that they still haven't solved :)

Gerhard

2005\12\01@170401 by Danny Sauer

flavicon
face
R. wrote regarding 'Re: [OT] newbie question on timing' on Thu, Dec 01 at 15:46:
> Olin Lathrop wrote:
> >R. I. Nelson wrote:
> >>most of the stuff I did was + or - 0.0005".  but we
> >>still tried and usually achieved 0 tolerance.
> >
> >Clearly not.  Saying stuff like this that obviously can't be true just
> >eliminates your credibility.  
>
> I think your credability has just been put in question with your above
> statement. www.mytoolstore.com/starrett/micro009.html.
> This one gives readings of  0.0001

You know that's still not 0, only "close enough" for some situations
to be considerd "effectively" 0, right?  I'm pretty sure the pedantic
point is that when you said "zero tolerance" you meant "close enough
to zero for our situation".  You could well be off by .00005 and still
read "zero" with that particular tool.  That's the great thing about
real numbers  / continuous scales - there's always an infinite number
of steps between one and the next, no matter how precise you get.

--Danny, probably not emphasising "pedantic" adequately

2005\12\01@171305 by Gerhard Fiedler

picon face
R. I. Nelson wrote:

>>> but we still tried and usually achieved 0 tolerance.

>> Saying stuff like this that obviously can't be true just eliminates your
>> credibility.  

> This one gives readings of  0.0001 [...] There are micrometers available
> that have a resolution of 0.00002" and accuracy of 0.000015"

What Olin was responding to is you saying that you achieved "0 tolerance".
When you measure that you're "right on" with an instrument that has 500 nm
tolerance, then you only know that you are within +-500 nm of the target.
(Simplified a bit.) You can turn and shake that as you like; that's a
tolerance of +-500 nm, and not a tolerance of 0. You won't find an
instrument with 0 tolerance, so you can't know whether you achieved 0
tolerance. You only ever will know what tolerance you have achieved within
the tolerance of the instrument you use to measure.

Gerhard

2005\12\01@195416 by R. I. Nelson

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Gerhard Fiedler wrote:

{Quote hidden}

The tolerance on the drawing  was +- 0.0005"  We had the ability,
experience, a magnified eye piece and a  measuring device that was
capable of reading  to an accuracy of 0.00005".  So being the means of
measurement was 10 times finer then the tolerance specs called for  I
think you can call ) out of tolerance parts.

What olin said that I was taking issue with is "Even if your tools told
you the error was 0,
that means it was only as close as the tool's accuracy and your ability
to read it."

If you want to discuss this further lets take it of list.



{Quote hidden}


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2005\12\02@071937 by olin piclist

face picon face
R. I. Nelson wrote:
>>> most of the stuff I did was + or - 0.0005".  but we
>>> still tried and usually achieved 0 tolerance.
>>
>> Clearly not.  Saying stuff like this that obviously can't be true just
>> eliminates your credibility.
>
> I think your credability has just been put in question with your above
> statement.

I think you're having a problem with the concept of zero.  It means nothing,
nada, zip, zilch.  There is no wiggle room on zero.  It doesn't matter how
far right of the decimal point the first significant digit is, if there is
one it's still not zero.

> www.mytoolstore.com/starrett/micro009.html.
> This one gives readings of 0.0001

So you're saying 0.0001 = 0?

> There are micrometers available  that have a resolution of 0.00002" and
> accuracy of 0.000015"

So now 0.000015 = 0?

> I can send alink to that if you are interested.

Please don't bother.  There is enough bad math out there already.  I don't
need to see any more.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\02@074453 by olin piclist

face picon face
R. I. Nelson wrote:
> The tolerance on the drawing  was +- 0.0005"  We had the ability,
> experience, a magnified eye piece and a  measuring device that was
> capable of reading  to an accuracy of 0.00005".
>
> What olin said that I was taking issue with is "Even if your tools told
> you the error was 0,
> that means it was only as close as the tool's accuracy and your ability
> to read it."

But that's exactly what you are describing.  In this case the tool's
accuracy and your ability to read it was 0.00005.  That's not zero and never
can be zero no matter how cleverly you extend the tools limits.  It's still
just plain wrong to say you measured an analog quantity to "0 tolerance".
If you say something like that in scientific or engineering circles you will
be dismissed as not knowing what you're talking about.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\02@101647 by R. I. Nelson

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I had a friend who was an engineer that " The day I remembered to factor
in everyday common sense I became an engineer"

I agree with most all of Olins statements.  However when you factor in
common sense. You have the margins set with a tolerance of  +-0.0005".
You have the tools to read to 0.00005".  You have apart that is supposed
to be 1" DIA.  It measures  1.0000" with calibrated mics any one with
common sense can call that a 0 tolerance part.

If you have any further comments lets take this off list.


Olin Lathrop wrote:

{Quote hidden}


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2005\12\02@105455 by olin piclist

face picon face
R. I. Nelson wrote:
> You have the margins set with a tolerance of  +-0.0005".
> You have the tools to read to 0.00005".  You have apart that is
> supposed to be 1" DIA.  It measures  1.0000" with calibrated mics any
> one with common sense can call that a 0 tolerance part.

No that's not common sense, just plain wrong.

What you are really saying is that the tolerance is below the level you care
about.  That's fine, and deciding what the level needs to be is part of
enginnering, but you don't have and never can have 0 tolerance.

There's enough public misundertanding about this concept that it's important
(in fact irresponsible not to) for us engineers and scientists to state it
correctly.  This sort of erroneous statement and imprecise use of terms
needs to be squashed whenever possible to avoid even more confusion and
misunderstanding by non-technical people.

Lest you think this is just theoretical agument, consider that
misunderstanding of this issue almost caused bad public policy.  Politicians
are fond of saying they support a "zero tolerance" to drugs.  A few years
back when this was codified into law, the original wording literally set the
acceptable level of drugs found at zero.  For example, the Coast Guard would
have been able to sieze your boat for finding any drugs at all.  Can you
guarantee that there are no opiate molecules on your boat?  Nobody ate a
poppy seed bun 2 years ago and dropped a seed?  If you set the level at
zero, then you are really setting it at whatever the tolerance of the
equipment on hand is to detect it.  This can vary widely making the
application of the law unfair, and it also changes over time as equipment
gets more and more sensitive.  I believe the law was eventually modified to
spell out a specific quantity before it was passed.

I'm sure there are other examples where this misunderstanding has caused
real harm.

So please, do yourself and everyone else a favor and stop making rediculous
claims of "0 tolerance" parts.  Since you're presumably a technical person
on this list you really should know better.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\02@120232 by Gerhard Fiedler

picon face
Olin Lathrop wrote:

> R. I. Nelson wrote:
>> You have the margins set with a tolerance of  +-0.0005".
>> You have the tools to read to 0.00005".  You have apart that is
>> supposed to be 1" DIA.  It measures  1.0000" with calibrated mics any
>> one with common sense can call that a 0 tolerance part.

I'd say you can call it a "1 inch part" without further going into details,
because a diameter that may vary from 0.99995" to 1.00005" is close enough
to 1" to justify that name, in most contexts, and specifically in your
context (where the required tolerance is bigger than the actual tolerance).

But don't call it a "0 tolerance part": you even /know/ the tolerance...
it's 0.00005", not 0". So why call it 0 if you know it isn't? What you seem
to try to say is "it's as close to the target as we can get with our
tools". But that's a long shot from "0 tolerance"... and "0 tolerance" in
this context sounds even a bit arrogant, in the sense of "our tools are the
best, and we are so close to the target that nobody can measure a
deviation". (Which, even if it were true, would still not create a "0
tolerance part" :)

> There's enough public misundertanding about this concept that it's
> important (in fact irresponsible not to) for us engineers and scientists
> to state it correctly.  

Olin's point about making sure the public (and that includes lawmakers)
gets a better understanding of what we do and deal with is quite important,
IMO.

Gerhard

2005\12\02@122625 by Alan B. Pearce

face picon face
>But don't call it a "0 tolerance part": you even
>/know/ the tolerance... it's 0.00005", not 0".

Close tolerance, not zero tolerance is the term that should be used.

2005\12\02@152317 by R. I. Nelson

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So if we have the best tools available to measure the part and they
measure the part at 1.0000".
now you come along and without ever seeing the part or measuring tools,
you state the part  cannot be 1.00000"  You are assuming it to be
incorrect, what are you using to base your assumption on.  You have to
have some means of proving your assumption or theory  or it is just an
UNPROVED  assumption or theory .

Until you could come into that work station with a device proven to be
more accurate by the Bureau of Standards.  How can you, with any
credibility,  say that our parts were not zero tolerance.

The company I had worked for used and told me to use the term "0
tolerance" when the part measured 1.00000" with the micrometers we had.




Gerhard Fiedler wrote:

{Quote hidden}


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2005\12\02@153656 by Richard Prosser

picon face
> The company I had worked for used and told me to use the term "0
> tolerance" when the part measured 1.00000" with the micrometers we had.
>


And they're wrong.
RP

2005\12\02@161800 by Gerhard Fiedler

picon face
R. I. Nelson wrote:

> So if we have the best tools available to measure the part and they
> measure the part at 1.0000".

Not really the best tools. Good tools, but you can be sure there are better
ones. (I think you yourself came up with a few links to vendors of betters
tools than the ones you were using.) Judging by the use of inches, you seem
to be US American of the old school. Check out the NIST site for some US
gov info about state of the art measurement precision.

> now you come along and without ever seeing the part or measuring tools,
> you state the part  cannot be 1.00000"  

I never said that. Please read what I wrote: '... may vary from 0.99995" to
1.00005"'. If my spotty knowledge of English as a second language doesn't
play games with me, that includes the possibility that it is in fact
1.00000" all around.

> You are assuming it to be incorrect, what are you using to base your
> assumption on.  

I take your word for it, nothing less. You said 'you have the tools to read
to 0.00005".' That's what I based my arguments on. Now did your tools have
a tolerance of 0.00005" or not?

> You have to have some means of proving your assumption or theory  or it
> is just an UNPROVED  assumption or theory .

I just assumed you were telling the truth (about the tolerance of your
instruments) and took it from there. So you tell me: did you tell the
truth?

> Until you could come into that work station with a device proven to be
> more accurate by the Bureau of Standards.  How can you, with any
> credibility,  say that our parts were not zero tolerance.

I can say, and I doubt you will find many that challenge that, that there
is no part -- not made by your company, not by others -- that is "zero
tolerance". Letting aside pride in your workmanship, did you read and
understand the arguments offered here? This is not to say you guys did not
a good or even outstanding job. I'm not the one to judge that, and never
did. But the concept of "zero tolerance" is something different, and by
principle impossible. Simply that.

> The company I had worked for used and told me to use the term "0
> tolerance" when the part measured 1.00000" with the micrometers we had.

Well, I'm sorry to hear that. It happens all the time that the boss is not
right, and to be able to bring food on the table, we all probably are at
times forced to let this go by without complaining too loudly. But that
doesn't make a wrong right. You should read and focus on the arguments
provided plenty here, and try to explain what you mean with "zero
tolerance" and try to find out whether that makes sense -- independently of
what your ex-boss said.

If you define "the best tools in a shop" define "zero tolerance"; well,
then I have seen some pretty crude "zero tolerance" pieces :)  If you
define "the best tools on the market" define "zero tolerance", then this is
a moving target, and some tools may be better in some respects while others
are better in others, and it's difficult to say which one defines in the
end the "zero tolerance" criterion. If you define "zero tolerance" with
"when the boss says it is", then we're in bad shape, too, as I'm pretty
sure my boss won't agree with yours. None of these definitions of "zero
tolerance" make a lot of sense to me. The only one that does make sense is
that "zero tolerance" means a tolerance of "+0 -0". And this is impossible
to measure.

So this meaning of "zero tolerance" is not possible, and that's what we
have been trying to explain so far. How do you define "zero tolerance" so
that it in fact /is/ possible? And that it is possible to achieve with
tools that have a tolerance of 0.00005"?

Gerhard

2005\12\02@174536 by olin piclist

face picon face
R. I. Nelson wrote:
> So if we have the best tools available to measure the part and they
> measure the part at 1.0000".
> now you come along and without ever seeing the part or measuring
> tools,
> you state the part cannot be 1.00000"

No, I said that it can't be "0 tolerance".

> You are assuming it to be
> incorrect, what are you using to base your assumption on.  You have
> to
> have some means of proving your assumption or theory or it is just
> an UNPROVED assumption or theory.

I've already explained this in what I thought was reasonable detail, yet you
persist in this rediculous assertion of "0 tolerance".

I give up.  Maybe others with more patience can jump in, or you can find
text on this.  I remember this was covered in 8th grade math class.

> The company I had worked for used and told me to use the term "0
> tolerance" when the part measured 1.00000" with the micrometers we
> had.

That just proves my point about this concept being widely misunderstood by
non-technical people.  Maybe you should show them the 8th grade math book
after you're done with it.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\02@180336 by Jinx
face picon face
> The company I had worked for used and told me to use the
> term "0 tolerance" when the part measured 1.00000" with
> the micrometers we had

A better term would have been "no significant difference" at
that resolution. For a QC statistical report, "0 tolerance" would
be generally accepted as meaning very close. To actually state
"0 tolerance" with certainty you'd have to measure to infinite
resolution, and with the possible exception of materials at 0K,
everything you measure and the thing you measure with will be
vibrating. "0 tolerance" at that resolution would be a probability,
never a certainty

2005\12\02@195659 by Howard Winter

face
flavicon
picon face
On Fri, 02 Dec 2005 14:24:03 -0600, R. I. Nelson wrote:

>...
> The company I had worked for used and told me to use the term "0
> tolerance" when the part measured 1.00000" with the micrometers we had.

This is a marketing department decision, and has nothing to do with engineering.  They can call it "0
tolerance", "nil error", "ultimate accuracy", or "magic measurement", the name does not affect the
engineering.  What you have is not zero tolerance, it's tolerance is lower than your ability to measure it,
that's all.

Cheers,



Howard Winter
St.Albans, England


2005\12\03@034735 by Bill & Pookie

picon face
Wasn't it the acceptance and management of tolerance that enabled items to
be mass produced?

Had a job of maintaining a tomatoes sorter out in the fields.  It used IR to
determine if a tomatoes was ripe and if it wasn't, it would kick it off the
line.  I took pleasure in watching it kick a nice red tomatoes off the line
occasional.  Knowing that if I kept the machine down for half a day to make
adjustments each time it dumped a ripe one, I would soon be out of a job.

Bill


{Original Message removed}

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