• Vaiseshika Electron Device

Kelvin Double Bridges For Low Resistance Measurement

Vaiseshika offers Kelvin double bridge instruments for measuring resistance. Type 9403 (Senior) is an important instrument in the measurement of very low resistances of the order of 0.1 micro, ohm. This is the only instrument which provides measurement techniques of high precision for extremely low resistances. The bridge has the capability to measure low resistance spanning from 0.02 micro ohm to 1.1 ohm. Ten standard resistors drawn from manganin sheets, each having a value of 0.001 ohm, are provided in the bridge. The slide wire is divided into 500 divisions to provide a resolution of 2 micro ohm. This slide wire is totally immersed in oil to ensure total stability of resistances in the bridge. Four terminals method is employed to obtain accurate results on the bridge. Type 9404 (Industrial) is an identical version of the Senior version. But the slide wire is of 0.01 ohm divided in 500 equal parts. Also it is not immersed in oil in this case. Further heavy duty terminals have been used to eliminate the errors due to contact resistance. Ten standard manganin resistance coils of 0.01 ohm are provided in this bridge. Separate terminals for current and potential leads are provided. Again silver to silver hard plated switches have been used for best results. Both instruments have wide ranging applications in cable industry, measurement of resistance in transformers, armature windings, temperature rise test of transformers and impurity determination in metal sheet and metal rod manufacturing industries.