INTRODUCTION
Measurements are required everywhere in the entire universe,
without measurement we can’t find anything. For example a day consists 24 hours
which indicates measurement. The earth revolves around the sun, one rotation
equals to 365 days which indicated in measurement. Not only in the subjects of
space every work is based on measurement. So the electricity has measurement
which indicates the different quantities
Measurement is a process by which one can
convert physical parameters to meaningful numbers.
There are two major
functions of all engineering branches.
1. Design of equipments and process
2. Proper operation and maintenance of equipment and process
Both these functions require measurements, this is because of
proper and economical design, operation and maintenance required a feedback
information, that`s why measurement plays a significant role in engineering.
Methods of Measurement:
The methods of measurement are broadly classified into two
types:
1. Direct Method
2. Indirect Method
1. Direct Method:
* In this method the unknown quantity is directly compared
against a standard.
* The result is expressed as a numerical numbers and units
* Direct methods are quite common for the measurement of
physical quantities like length, mass, time.
2. Indirect Method:
Direct methods are not
always possible in practical manner and also not fissible. Direct method in
most of cases are inaccurate because human factors involvement is more, they
are also less sensitive, hence direct methods are not preferred and are rarely
used
*In engineering application measurement systems are used
which required mean of indirect methods for measurement purpose.
Instruments and measurement system:
Measurements involve the use of instruments as a physical
means of determining quantities.
*The various instruments are mechanical, electrical and
electronics.
* Electrical instruments are mainly classified into two types
shown below:
Absolute Instruments:
These instruments measures in terms of constant and their deflection.
The example for Absolute instrument is Tangent galvanometer which indicates the
current values in terms of deflecting angle, radius and horizontal component of
earth`s field.
*The tangent galvanometer is used in the physics experiments
for analysis of magnetic field when magnets placed near to it.
Secondary Instruments:
These instrument measures the electricity in the form of deflection only
when they have been pre-calibrated by comparison with absolute instrument.
i) Indicating Instruments:
The
instruments which are used for measuring electricity and indicated with a
pointer moving over a measuring scale.
Example: Ammeters, Voltmeters, Wattmeter’s.
ii) Recording Instruments:
The instrument gives continuous record of the variations in the
measuring along with the time. The instrument consists of ink pen mounted on a
graph which moves at moderate speed along the perpendicular direction of the
pen.
iii) Integrating Instruments:
These instruments are digital types and works completely on electronics.
These instrument can measure and register by a set of dials and pointers. When
supply is given to this instrument it can measure electricity in the form of
Amp-hours or KWH. A simple designed program is inserted in the instrument which
give accurate values while measuring electricity.
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