UNIT – 3

COMPARISON METHODS OF MEASUREMENTS
w D.C & A.C potentiometers
w D.C & A.C bridges
w transformer ratio bridges
w self-balancing bridges
w Interference & screening
w Multiple earth and earth loops
w Electrostatic and electromagnetic interference
w Grounding techniques.

Potentiometers
w DC Potentiometers.
w AC Potentiometers.
A Potentiometer is an instrument designed to measure an unknown voltage by comparing it with a known voltage.

Bridges

Ø DC bridge
Ø AC bridge.

Resistance
w Low Resistance(<1v)> 0.1M V)
Low Resistance(<1v) color="#ff0000">Medium Resistance(1V to 0.1M V)
w Ammeter-voltmeter method
w Substitution method
w Wheatstone bridge method
w Ohmmeter method
Wheat stone Bridge
High Resistance(> 0.1M V)
w Direct deflection method
w Loss of charge method
w Meg ohm bridge
w megger
Inductance
w Measurement of self Inductance
Ø Maxwell’s Inductance bridge
Ø Maxwell’s Inductance- capacitance bridge
Ø Hay’s bridge
Ø Owen’s bridge
Ø Anderson’s bridge
w Measurement of mutual Inductance
Ø Heaviside mutual Inductance bridge
Ø Carey foster bridge Heydweiller bridge
Ø Campbell’s bridge
Maxwell’s Inductance Capacitance Bridge
Capacitance
w De sauty’s bridge
w Schering bridge
Schering Bridge
Frequency
w Wien’s Bridge.
Transformer Ratio Bridge
w They are replacing the conventional AC bridge.