A simple build-up method for the DC voltage scale of a source

We report on the performance of a simple method, known as the Reference Step Method, to build up the dc voltage scale of a source. The key advantages of this method are that it relies on equipment that is readily available in most high-level laboratories and can be fully automated. The Type A uncertainties achieved by this approach can be less than 0.1 μV/V. This performance is achieved because of the excellent differential linearity of the DMM used in the method. We are validating the accuracy of the method by directly comparing this approach with more traditional resistive divider techniques.