Very low resistance, which is less than one ohm, could be measured using:
The resistances are classified depending upon the values as:
The methods used for the measurement of low resistances are:
Ammeter Voltmeter Method:
Connecting voltmeter across the load is suitable for low resistance measurements.
Ammeter reading is:
\(I+I_V=\frac{E(R+R_V)}{R.R_V}\)
Voltmeter reading = E
The calculated resistance is:
\(\frac{E}{I+I_V}=\frac{R.R_V}{R+R_V}\)
Kelvin's Double Bridge Method: Kelvin's Double Bridge Method is a modification of the Wheatsone bridge method.
The circuit diagram is shown below:
R is the unknown resistance and S is the standard resistance.
Potentiometer Method:
Note:
Type of Bridge 
Name of Bridge 
Used to measure 
Important 
DC Bridges 
Wheatstone bridge 
Medium resistance 

Corey foster’s bridge 
Medium resistance 


Kelvin double bridge 
Very low resistance 



Mega ohm bridge 
High resistance 


Megger 
High insulation resistance 
Resistance of cables 
AC Bridges 
Maxwell’s inductance bridge 
Inductance 
Not suitable to measure Q 
Maxwell’s inductance capacitance bridge 
Inductance 
Suitable for medium Q coil (1 < Q < 10) 

Hay’s bridge 
Inductance 
Suitable for high Q coil (Q > 10), slowest bridge 

Anderson’s bridge 
Inductance 
5point bridge, accurate and fastest bridge (Q < 1) 

Owen’s bridge 
Inductance 
Used for measuring low Q coils 

Heaviside mutual inductance bridge 
Mutual inductance 


Campbell’s modification of Heaviside bridge 
Mutual inductance 


DeSauty’s bridge 
Capacitance 
Suitable for perfect capacitor 

Schering bridge 
Capacitance 
Used to measure relative permittivity 

Wein’s bridge 
Capacitance and frequency 
Harmonic distortion analyzer, used as a notch filter, used in audio and highfrequency applications 