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Old 29th March 2011, 07:33   #31
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Default Re: Just a thought - Units of measurement

@Samurai and @ Spike

I thoroughly enjoyed the discussion on "Parallax". It took me to my school days and as if I was watching two kid fighting for "who is right". (Please excuse me for this, it is in +ve sense) and they are now deftly handled by headmaster (sutripta Da ,sorry).

BTW @ Sutripta are you from a process or oil industry ?

Counter view :
All measurements are fraught with errors inherently. That means nothing can ever be measured perfectly error free. In-spite of parallax free Caliper.

Cheers
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Old 29th March 2011, 13:27   #32
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Default Re: Just a thought - Units of measurement

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Originally Posted by sanagg1 View Post
I thoroughly enjoyed the discussion on "Parallax". It took me to my school days and as if I was watching two kid fighting for "who is right".
Except one of the kids learned parallax error before the other was born.

In the early 80s, I used to be a regular competitor in science fairs conducted by VITM. So I learned practical aspect of many scientific principles while in high school. For example, when my older cousin was studying about telegraphy in 3rd year BE, I had created a working model of it in 10th grade and entered it into the science fair exhibition. She was impressed enough to lend her engineering textbook to me for learning more. It was a Telegraphy book by N.N.Biswas, which I had to study again 5 years later in B.E syllabus.

VITM still conducts those science fairs: The Hindu : Kerala / Kannur News : State emerges top at Southern India Science Fair
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Old 29th March 2011, 14:04   #33
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Default Re: Just a thought - Units of measurement

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Originally Posted by Samurai View Post
Except one of the kids learned parallax error before the other was born.
Correct, the kid although born late, learned the "correct connotation" of parallax error and continues to use it (judiciously) daily for his living.

Spike
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Old 29th March 2011, 15:08   #34
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Default Re: Just a thought - Units of measurement

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Correct, the kid although born late, learned the "correct connotation" of parallax error and continues to use it (judiciously) daily for his living.
Yet, you failed to understand I had used it correctly.

In future, please try to give some benefit of doubt to others before claiming they are wrong.
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Old 29th March 2011, 15:39   #35
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Default Re: Just a thought - Units of measurement

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In future, please try to give some benefit of doubt to others before claiming they are wrong.
In future benefit of doubt will be kept in mind because of the terminologies used. Diameter is referred to as thickness and so on. See below post.

Quote:
Originally Posted by Samurai View Post
When I say thickness, I mean the outer-to-outer distance or diameter of the pipe.
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Originally Posted by Sutripta View Post
Yes. Because the thimble and sleeve are at different distances from the eye. In fact in a micrometer with a vernier, it can lead to an error of a couple of counts. Incidentally, one can design a vernier caliper with no parallax error.
Sam, I think you have still not understood about parallax error. I was stressing on "error" and I feel you were stressing on "precision / LC". Have you seen anyone measuring the tire width using a screw gauge? NO, I don't think so. Read the above post of Sutripta ^^ (stress on eye levels).

Quote:
Yet, you failed to understand I had used it correctly.
Read the below posts to understand.

Quote:
Originally Posted by Samurai View Post
Just measuring tape, won't that create parallax error? I am assuming you mean sidewall to sidewall.
Quote:
Originally Posted by Samurai View Post
I thought Screw Gauge eliminated parallax error. Please explain how parallax error can happen in screw gauge?
These posts suggest measuring tape leads to parallax error and micrometer does not, which IS GROSSLY WRONG!!!

Spike

Last edited by SPIKE ARRESTOR : 29th March 2011 at 15:40.
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Old 29th March 2011, 16:18   #36
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Default Re: Just a thought - Units of measurement

Fortunately, I don't need to have the last word on everything. So I shall move on.
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Old 29th March 2011, 20:24   #37
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Default Re: Just a thought - Units of measurement

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That error is so very minute when compared to the width of a tyre. A fraction of a millimeter at the most.
Also agreed. Actually it will be around 1/200 of screw pitch at most.

Quote:
Originally Posted by sanagg1 View Post
@Samurai and @ Spike
BTW @ Sutripta are you from a process or oil industry ?
No. But I guess you are from the oil industry. Though Jorhat seems a bit odd.

Regards
Sutripta

Last edited by Sutripta : 29th March 2011 at 20:26.
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Old 30th March 2011, 12:36   #38
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Default Re: Just a thought - Units of measurement

Quote:
Originally Posted by Sutripta View Post
Also agreed. Actually it will be around 1/200 of screw pitch at most.


No. But I guess you are from the oil industry. Though Jorhat seems a bit odd.

Regards
Sutripta
your guess is spot on.

Jorhat is in Assam state. Assam produce roughly 3 million MT of oil per annum.

BTW Assam is highest oil producing state after Gujarat.

regards
Sanagg1
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Old 30th March 2011, 14:03   #39
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Default Re: Just a thought - Units of measurement

^^^
Hi,
I would have understood Sibsagar, or the Digboi- Tinsukia- Dibrugarh area and oil. Jorhat is an odd man out.

Regards
Sutripta
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Old 14th October 2013, 16:46   #40
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Default 1 Litre - is it 1000ml or 1000cc?

My father used to call me dim-witted. I have always protested it. I would rather call myself a slow burner. Today, I realized how slow a burner I am. After spending years talking about cars and engines, only today did I get a very basic Physic doubt while discussing engine power and displacement .

In automobile terminology, a 1000cc (cubic centimetre) engine is simply called a 1 Litre engine.
In volumetric terminology, 1000ml is equated to 1 Litre.

Isn't there a 'seemingly disparate' inequality in the 2 definitions. In metric unit terminology, a centi is bigger than a milli (10 milli is 1 centi). Then, how could 1000ml be same as 1000cc?? (there should be something fundamentally wrong with the engine of the physics under the hood of the car industry )

I went back to my school Physics book to relearn the basics (yeah, I'm kidding; why trouble the books when you have Google). Here's what I understood.

Solids are measured in terms of Mass or Weight; hence the terminologies Kilogram, gram and sub-units.

Whereas Liquids, since the property of a liquid (and also gas) changes with pressure and temperate, and that they take the shape of the medium, measurements are in terms of Volume under standard temperate and pressure.

A Litre is defined as the volume of 1 kilogram of pure water at maximum density and standard pressure. Now, 1L = 1 Kg (though not accurately).

Here we are equating volume against Mass, hence the perception of disparity in scale of measurement (Refer the scale chart at the end of post).

Now let's understand measurement of engine displacement. Fuel burns at different temperatures and pressure depending on engine, fuel density and type of fuel. So, standard measurement of displacement is not easy or direct in volumetric terms (of fluid). Instead, the measurement is in terms of space of the container (here cylinder).

1 Litre (1000ml) of water would fill up fully in a cube of dimension 10cm x 10cm x 10cm. So, 1 Litre (volume) equates to 1000 cubic centimetre of 3d space. This measurement is standard irrespective of pressure, fuel density and temperature. Since 10 cm - 1 decimetre, it also implies:

1 Litre = 1000cc = 1 cubic decimeter.


Standardizing volume, mass, space (length); we get, under normal temperature and pressure -

1 Kg (Mass) = 1 L (Volume) = 1 dm^3 (3d Space)

Mods: Guess most of Team BHPians might have already known these basic concepts. I thought it could be worth sharing here. Please remove if not suitable for this forum. Thanks!
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Last edited by arunkrishnan4 : 14th October 2013 at 17:11.
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Old 14th October 2013, 18:11   #41
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Default Re: 1 Litre - is it 1000ml or 1000cc?

I don't remember the exact proof now, but 1ml = 1cc.

The 1 litre = 1000ml = 1000cc is just so there is congruity between length and volumetric measurements.
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