Kelvin Double Bridge is used to measure the value of low resistance of the order of 1? . In our set up the range is from 1? to 120 ?. Kelvin Bridge is a modification of Whetstone Bridge and provides greatly increased accuracy in measurement of low value of resistance. Kelvin Double Bridge incorporates the idea of a second set of ratio arms (hence the name double bridge) use of four terminal resistors for the low resistance arms. This bridge is used for the measurement of unknown resistance in terms of comparison with a standard capacitance using the following equation
Cx = C3 (R1/R2)
In this bridge we are having three sections. A built in oscillator section. Bridge section with four arms. Arm AC consists of standard fixed capacitance. Arm AD consists of unknown capacitance Cx. Arm DB consists of non-inductive resistance R2 with multiple range of selection. Arm BC consists of parallel network between variable resistance R1 of 10k? & variable capacitance of (100 ? 1KPF). The balance of bridge can be observed using a built-in audio amplifier with loudspeaker arrangement. This acts as a null detector.
Ranges of Measurement is from (0.1?FD ? 0.001?FD) Methods for Measurement of Low Resistance
?Ammeter Voltmeter Method
?Kelvins Double Bridge Method
?Potentiometer Method |
