Introduction to
measuring instruments
Measurements play
an important role in achieving goals and objectives of Engineering.
Measurements are basically a means of communication and are used by scientists
for understanding natural phenomenon, by the society for transacting business
and by the engineers for practical ends. The advancement of science and
technology is dependent upon a parallel progress in measurement techniques. The
reason for this are obvious. The importance of measurement is simply and
eloquently expressed in the following statement of the famous physicist
Lord Kelvin.
“I often
say that when you can measure what you are speaking about and can express it in
numbers, you know something about it; when you cannot express in it numbers your
knowledge is of a meagre and unsatisfactory kind.”
Measurement is
essentially a process in which the magnitude of a quantity is determined in
comparison with another similar quantity.
Measurements involve
the use of instruments as a physical means of determining quantities or
variables. The instrument serves as an extension of human faculties and enables
the man to determine the value of unknown quantity or variable which his
unaided human faculties cannot measure, a measuring instrument exists to provide
information about the physical value of some variable being measured. In simple
cases, an instrument consists of a single unit which gives an output reading or
signal according to the unknown variable applied to it. In more complex
measurement situations, a measuring instrument may consists of transducing
elements which convert the measurand to an analogous form. The analogous signal
is then processed by some intermediate means and then fed to the end devices to
present the results of the measurement for the purpose of display and/or
control. Because of the modular nature of the elements within it, it is common
to refer the measuring instruments as a measurement system.
The first
instrument used by mankind were mechanical in nature and the principles on
which these instruments worked are even in vogue today. The earliest scientific
instruments used the same three essential elements as our modern instruments
do. These elements as
(a)
A detector,
(b)
An intermediate transfer device, and
(c)
An indicator or recorder or a storage
device.
Modern science
and technology is associated with sophisticated methods of measurements and
measuring instruments.
The history
of development of instruments gives three phases of instruments, viz.:
1.
Mechanical instruments
2.
Electrical instruments, and
3.
Electronic instruments
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