ELECTRICAL AND ELECTRONIC MEASUREMENTS

GATE SYLLABUS:

Electrical and Electronic Measurements:
Bridges and potentiometers; PMMC, moving iron, dynamometer and induction type instruments; measurement of voltage, current, power, energy and power factor; instrument transformers; digital voltmeters and multimeters; phase, time and frequency measurement; Q-meters; oscilloscopes; potentiometric recorders; error analysis.

UNIT-I Measuring Instruments:
Classification – deflecting, control and damping torques – Ammeters and Voltmeters – PMMC, movingiron type instruments – expression for the deflecting torque and control torque – Errors and compensations, extension of range using shunts and series resistance. Electrostatic Voltmeters-electrometer type and attracted disc type – Extension of range of E.S. Voltmeters.

UNIT –II Instrument transformers:
CT and PT – Ratio and phase angle errors – design considerations Type of P.F. Meters – dynamometer and moving iron type – 1-ph and 3-ph meters – Frequency meters – resonance type and Weston type –synchroscopes.

UNIT –III Measurement of Power:
Single phase dynamometer wattmeter, LPF and UPF, Double element and three element dynamometer wattmeter, expression for deflecting and control torques – Extension of range of wattmeter using instrument transformers – Measurement of active and reactive powers in balanced and unbalanced systems.

UNIT –IV Measurement of Energy:
Single phase induction type energy meter – driving and braking torques – errors and compensations –testing by phantom loading using R.S.S. meter. Three phase energy meter – trivector meter, maximum demand meters.

UNIT – V Potentiometers:
Principle and operation of D.C. Crompton’s potentiometer – standardization – Measurement of unknown resistance, current, voltage. A.C. Potentiometers: polar and coordinate types standardization – applications.

UNIT – VI Resistance Measurements:
Method of measuring low, medium and high resistance – sensitivity of Wheat stone’s bridge – CareyFoster’s bridge, Kelvin’s double bridge for measuring low resistance, measurement of high resistance –loss of charge method.

UNIT –VII A.C. Bridges:
Measurement of inductance, Quality Factor - Maxwell’s bridge, Hay’s bridge, Anderson’s bridge, Owen’s bridge. Measurement of capacitance and loss angle - Desauty bridge. Wien’s bridge – Schering Bridge.

UNIT – V III  Magnetic Measurements:
:Ballistic galvanometer – equation of motion – flux meter – constructional details, comparison with ballistic galvanometer. Determination of B-H Loop methods of reversals six point method – A.C. testing – Iron loss of bar samples– core loss measurements by bridges and potentiometers.