UNIT I MEASURING INSTRUMENTS Period
Definition of Measurement – Definition of True Value, Accuracy, Precision, Error and
Error Correction, Instrument Efficiency – Classifications of Analog Instruments
(Indicating, Recording and Integrating) – Operating Forces (Deflecting force,
Controlling force & Damping force).
Construction, Working and Torque Equation of Permanent Magnet Moving Coil
Instrument and Moving Iron Instruments (Repulsion and Attraction type) – Extension
of Instrument Range using Shunts and Multipliers – CT and PT – Construction and
Working of Multimeter, Megger and Earth Tester.
Construction and Working of: Single Phase Electro Dynamometer type Wattmeter –
Single Phase Energy Meter – Three Phase Energy Meter – Digital Energy Meter –
Introduction about Power Factor Meter, Frequency Meter and Phase Sequence
Indicator – Block Diagram of CRO.
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Practical Exercises:
Ex.No Name of the Experiment Period
1 VOLTAGE, CURRENT AND POWER MEASUREMENT IN SINGLE PHASE
AC CIRCUIT.
Activities to Perform:
a) Conduct an experiment to measure voltage, current and power in
single phase a.c circuit by using Voltmeter, Ammeter and
Wattmeter respectively for different loads.
b) Repeat the same experiment by replacing above meters with
single Digital Power Monitor.
c) Compare and Discuss the observations.
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2 CALIBRATION OF AMMETER AND VOLTMETER
Activities to Perform:
i) Conduct an Experiment to calibrate the given Ammeter and
Voltmeter with corresponding standard meters.
ii) Plot the Error Curve.

3. MEASUREMENT OF CURRENT IN THREE PHASE CIRCUIT BY USING
SINGLE AMMETER
Activities to Perform:
i) Connect single Ammeter in three phase circuit through Ammeter
Selector Switch (ASS) and Current Transformers.
ii) Measure current in R, Y and B phases by using single Ammeter
for balanced and unbalanced load.
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4. CALIBRATION OF ENERGY METER
Activities to Perform:
i) Conduct an Experiment to calibrate the given Three Phase Energy
Meter using Wattmeter and Stop Clock.
ii) Plot the Error Curve.
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5 MEASUREMENT OF RESISTANCE USING WHEATSTONE BRIDGE
Activities to Perform:
i) Discuss the theory of Wheatstone Bridge.
ii) Conduct an Experiment to measure the value of armature winding
resistance using Whetstone Bridge.
iii) Compare the observed value of resistance with theoretical /
calculated value.
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6 MEASUREMENT OF EARTH RESISTANCE BY USING EARTH TESTER.
Activities to Perform:
i) Discuss the Necessity of maintaining Earth Resistance as Low
Value.
ii) Discuss the Permissible Earth Resistance Value as per Indian
Standard.
iii) Conduct an Experiment to measure the Earth Resistance by using Earth Tester