Kelvin’s Bridge
Modified version of Wheatstone's bridge
measuring range -1 micro ohm to 1 ohm
Uses a second set of ratio arms
Called Kelvin’s double bridge
Eliminates the effects of contact & lead
resistnace
For bridge to balance
Rx = R2. R3 / R1
Rb/ Ra = R3 /R1
Mega Ohm bridge
used to measure high resistance
Range 0.1 to 10 6 M Ω
Accuracy - 3 %
Eqlt. For high resistance
A high resistance
Guard terminal to insulator
Mega ohm meter
High gain amplr
Balancing bridge
Ac bridges
Based on Wheatstone bridge principle
To measure L & C
Appln. In communication & complex
electronic circuits
Used for phase shifting, providing feed back
path for oscillators & ampr, filtering,
measuring frequncy
I1 Z1 = I2 Z3
I1 Z2 = I2 Z4
Z1/ Z2 = Z3 / Z 4
Z1 Z 4 = Z2 Z3
Similar angle bridge
Also called Capacitive comparison bridge
Series Resistance capacitive bridge
Used to measure impedance of capacitive ckt.
Independent of frequency
Thank u
Similar angle bridge
Maxwell bridge
To determine unknown resistance
With capacitance standard
(C not affected by external field,cheap, small
in size)
Also called Maxwell- Wein bridge
For measuring L with low Q (< 10)
Hay bridge
Used to measure R & L where resistance is a
small fraction of reactance Xl.
Used for coil with high Q
Replacing capacitor for measurement in
similar angle bridge
Opposite Angle bridge
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