Calibration

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Lesson 11 Calibration
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Engineers, turned first to parts of the body, for
measuring instruments.
However, this was not a positive fixed dimension
or a standard.
Measurements must be standard to mean the same
thing to everyone
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In 1793, the French government adopted a new
system of standards called the metric system.
In 1824, the English Parliament legalized a new
standard yard which had been made in 1760. It
was a brass bar containing a gold button near
each end.
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What is Calibration?

• Act of comparing an instrument's measuring
  accuracy to a known standard

• The process of adjusting an instrument, to
  establish a set of values for correct operation

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MICROMETER
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(No Transcript)
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Notes
Info about screw reqd
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The cubit of Noah's time was the length of a
man's forearm or the distance from the tip of the
elbow to the end of his middle finger. Many times
this was useful, because it was readily
available, convenient, and couldn't be mislaid.
However, it was not a positive fixed dimension or
a standard. While the cubit is no longer used as
a unit of measurement, there are many customary
standards that originated in about the same way.
Our foot-rule started out as the length of a
man's foot. So, in the early days of history, the
foot varied in length, sometimes as much as 3 or
4 inches. Once the ancients started using arms
and feet for measuring distance, it was only
natural that they also thought of using fingers,
hands and legs. They also may have discovered
that some surprising ratios existed in body
measurements. What is now called an inch
originally was the width of a man's thumb. It
also was the length of the forefinger from the
tip to the first joint. Twelve times that
distance made a foot. Three times the length of
the foot was the distance from the tip of a man's
nose to the end of his outstretched arm. This
distance very closely approximates what is called
the yard. Two yards equaled a fathom which,
thousands Going as far back in time as Noah's
ark, the lack of a yardstick was not a serious
drawback. Most measuring was done by one
craftsman completing one job at a time, rather
than assembling a number of articles piecemeal to
be assembled later, it didn't make much
difference how accurate the measuring sticks were
or even how long they were. Generally, it doesn't
make much difference how long is a mile, yard or
inch or how heavy is a pound or ounce. What is
really important is that everyone means the same
thing when referring to each unit of measurement.
Measurements must be standard to mean the same
thing to everyone. of years ago, was the distance
across a man's outstretched arms. Half a yard was
the 18-inch cubit, and half a cubit was called a
span, which was the distance across the hand from
the tip of the thumb to the tip of the little
finger when the fingers were spread out as far as
possible. A hand was half a span. For thousands
of years, this was the way people measured
comparatively short distances. Each succeeding
civilization added its it to mankind's knowledge,
building an accumulation of measuring standards
and techniques. Some contributed weight measures.
Others showed us how to measure time. Still
others gave us methods for
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Going as far back in time as Noah's ark, the lack
of a yardstick was not a serious drawback. Most
measuring was done by one craftsman completing
one job at a time, rather than assembling a
number of articles piecemeal to be assembled
later, it didn't make much difference how
accurate the measuring sticks were or even how
long they were. Generally, it doesn't make much
difference how long is a mile, yard or inch or
how heavy is a pound or ounce. What is really
important is that everyone means the same thing
when referring to each unit of measurement.
Measurements must be standard to mean the same
thing to everyone. The cubit of Noah's time was
the length of a man's forearm or the distance
from the tip of the elbow to the end of his
middle finger. Many times this was useful,
because it was readily available, convenient, and
couldn't be mislaid. However, it was not a
positive fixed dimension or a standard. While the
cubit is no longer used as a unit of measurement,
there are many customary standards that
originated in about the same way. Our foot-rule
started out as the length of a man's foot. So, in
the early days of history, the foot varied in
length, sometimes as much as 3 or 4 inches. Once
the ancients started using arms and feet for
measuring distance, it was only natural that they
also thought of using fingers, hands and legs.
They also may have discovered that some
surprising ratios existed in body measurements.
What is now called an inch originally was the
width of a man's thumb. It also was the length of
the forefinger from the tip to the first joint.
Twelve times that distance made a foot. Three
times the length of the foot was the distance
from the tip of a man's nose to the end of his
outstretched arm. This distance very closely
approximates what is called the yard. Two yards
equaled a fathom which, thousands of years ago,
was the distance across a man's outstretched
arms. Half a yard was the 18-inch cubit, and half
a cubit was called a span, which was the distance
across the hand from the tip of the thumb to the
tip of the little finger when the fingers were
spread out as far as possible. A hand was half a
span. For thousands of years, this was the way
people measured comparatively short distances.
Each succeeding civilization added its it to
mankind's knowledge, building an accumulation of
measuring standards and techniques. Some
contributed weight measures. Others showed us how
to measure time. Still others gave us methods for
surveying big areas of land and establishing
boundaries. In techniques for measuring weights,
the Babylonians made important improvements upon
the invention of the balance. Instead of just
comparing the weights of two objects, they
compared the weight of each object with a set of
stones kept just for that purpose. In the ruins
of their cities, archaeologists have found some
of these stones finely shaped and polished. It is
believed that these were the world's first weight
standards. The Babylonians used different stones
for weighing different commodities. In modern
English history, the same basis has been used for
weight measurements. For the horseman, the
"stone" weight was 14 pounds. In weighing wool
the stone was 16 pounds. For the butcher and
fishmonger, the stone was 8 pounds. The only
legal stone weight in the imperial system was 14
pounds. The Egyptians and the Greeks used a wheat
seed as the smallest unit of weight, a standard
that was very uniform and accurate for the times.
The grain is still in limited use as a standard
weight. However, wheat seeds are no longer
actually put in the pan of the balance scale.
Instead, a weight that is practically the same as
that of an average grain of wheat is arbitrarily
assigned to the grain. The Arabs established a
small weight standard for gold, silver and
precious stones which very often were a part of
trade or barter deals. To weight the small
valuable quantities, they used as a weight
standard a small bean called a karob. This was
the origin of the word carat which jewelers still
use to express the weight of gems and precious
metals. In trading between tribes and nations,
many of these methods for measuring weights and
distances gradually became intermixed,
particularly by the Romans who spread this
knowledge throughout the known world at that
time, also adding some standards of their own. As
the Roman soldiers marched, they kept track of
the distance they traveled by counting paces. A
pace was the distance covered from the time one
foot touched the ground until that same foot
touched the ground again, or the length of a
double step.