Measuring Instruments
Electrical Measuring Instruments are divided into its two types which are Absolute instruments / Primary
instruments and Secondary instruments.
Measuring instruments
are classified into its many types and its classification is shown below:
Absolute / Primary Instruments
These are the instruments which give the value of the quantity
measured according to the constants of the instrument and its deflection. Primary
instruments are mostly used in standard laboratories and as a standardising
in various institutions and research organizations. The example of absolute
instruments are Rayleigh current
balance, absolute electrometer and tangent galvanometer. Tangent
Galvanometer gives the value of the current according to the tangent of
deflection angle Θ, the earth’s magnetic field and the radius and the number of
turns of the wire used in it. These instruments do not require comparison with
other standards.
Secondary Instruments
Secondary instruments are the instruments in which the value of the electrical quantity is measured and is determined from the deflection of the instruments. These instruments provide the magnitude
of the electrical quantity which is to be measured. These instruments are
already calibrated as compared to absolute instruments. Secondary
instruments are classified into its following
types:
- Indicating Instruments
- Integrating Instruments
- Recording Instruments
Indicating Instruments
Indicating instruments indicate the magnitude of an
electrical quantity which is to be measured with respect to time. The pointer
mounted on a moving system shows the indications on a calibrated scale. These
instruments are categorized into ammeters, voltmeters, watt
meters, frequency meters, power factor meters etc.
Integrating Instruments
These instruments measure the total amount of electricity
or electric energy supplied to it with a part of time. These instruments
measure the electricity in ampere-hours. These instruments provide readings
with the product of electricity and time. These instruments include ampere-hour
meters and energy meters in its category.
Recording instruments
As we understand its function from its name that it keeps record
of the variations in the magnitude of an electricity with the passage of
time. These instruments consist of moving system which carries a pointer
and a curve is traced which shows the variations in the magnitude of the
electrical quantity with the period of time. These instruments are used in power
houses for the measurement of electric current, voltage, electric
power etc. These instruments are available in different ranges for the
measurement of various electrical units.