WE Know that in our daily life as the electrical measurement purpose we need some instruments to electric quantities such as the [ current,voltage,power,frequency,power factor etc....]
In General The measuring Instruments are classified as two types
1) Absolute Instruments
2) Secondary Instruments
1) Absolute instruments :
1. Which give the value of the quantity to be measured
2. In terms of instrument constants
3. Where no previous calibration or comparison is required
Eg:1.Tangent Galvanometer
2.Reyleigh’s current Balance
2) Secondary Instruments :
1. Which are pre-calibrated with the help of absolute instruments or some other secondary instruments
2. Determined from the deflection of the pointer
Most generally used
These secondary instruments are again classified into
1. Indicating instruments
2. Recording instruments
3. Integrating instruments
1. Indicating Instruments :
~Indicate instantaneous value of electrical quantity
at the time of measurement only
Eg:1.Ammeter
2.Voltmeter
3.Wattmeter etc
2. Recording Instruments :
~Instead of indication
By means of a pointer and scale
~Give continuous record of the variations of the quantity
Over a selected period of time
E.g.:Instruments used in power stations
3. Integrating Instruments :
~Measure more than one quantity
Integrate into useful results
Eg:1.Energy meter
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