Hamon-Guarded Network to Increase the Accuracy of the Transfer of the Resistance Unit up to 1 at INRIM

In the framework of the revision and optimization of the measurement techniques for high-resistance measurements at the National Institute of Metrological Research (INRIM), a 100 MOmega-step Hamon-guarded network was projected and built. With this transfer standard, the 2sigma uncertainty of the maintained 1 GOmega standard at INRIM is now on the order of 7.0 times 10^-6 at a measurement voltage of 100 V. Details of the Hamon network and stability data in parallel configuration are given and discussed. The result of a verification of the performance of the Hamon network with a measurement method based on a digital multimeter (DMM) and a dc voltage calibrator (DcVC) is reported. A description of the measurement steps from 10 kOmega to 1 GOmega together with an uncertainty budget is also reported.