Quasi-Balance Four-Terminal Resistance Bridge

A kind of quasi-balance four-terminal ac resistance bridge has been constructed. The electronic inductive voltage divider provides high accurate voltage ratios for the bridge at a wide frequency range from 20 Hz to 10 kHz. The Wagner network with electronic circuit containing followers and amplifiers makes the voltage ratio unaffected by internal loading of ratio winding. Amplifiers are used to eliminate voltage drop on the lead wire connecting two resistors. Sampling method is used to measure the complex voltage ratio. The bridge can measure resistances from 1 Ω to 1 MΩ. The optimal uncertainty for resistance of 100 Ω and 1 kΩ is 2 × 10^-7 at 1 kHz.