An automated guarded bridge system for the comparison of 10 k/spl Omega/ standard resistors

An automated guarded resistance bridge has been specifically developed at the National Institute of Standards and Technology (NIST) for the calibration of high-quality 10 k/spl Omega/ standard resistors. The system is designed to compare up to 30 nominally equal, four-terminal resistors with a resolution and combined relative standard uncertainty of 0.01/spl times/10/sup -6/ and 0.02/spl times/10/sup -6/, respectively. It features a self-balancing detector circuit, and a programmable coaxial connector switch for selecting resistors. With a few minor modifications, the system is capable of comparing other nominally equal resistors in the range 100 /spl Omega/ to 1 M/spl Omega/.