Automatic DC voltage precision resistive divider with ratios between 10:1 and 107:1

At INRIM a DC Voltage precision resistive divider performing decade ratios from 10:1 to 107:1 was built. It can be automatically calibrated with a top-class calibrator and a precision multimeter calibrated in terms of deviation from linearity. It is made up of 90 kΩ, 9 kΩ, 900 Ω, 90 Ω, 9 Ω, 0.9 Ω, 90 mΩ and 10 mΩ bulk metal foil resistors connected in series, in four-terminal configuration. Peculiarities of the calibration method of the divider are: the evaluation of the DMM input impedance to correct its readings minimizing the load error and a solution to reduce the emfs effect of the relays. These operations are made during the calibration of the divider. The calibration and use uncertainties of the divider span respectively from 6.1 × 10 7 to 5.9 × 10 4 and from 6.7 × 10 7 to 6.5 × 10 4. The project is transferable to secondary laboratories in the framework of the INRIM knowledge transfer task.