Project of an automated Multiple Decade Ratios Precision Divider for Generation of low DC Voltages

At the National Institute of Metrological Research (INRIM) an automatable precision DC voltage fixed-ratios divider allows the division ratios of DC Voltages from 10:1 to 107:1. It can be quickly calibrated when necessary and involved in traceability transfer. Its resistors are selected bulk metal foils ones connected in series in four terminal configuration whose values are 90 k, 9 k, 900 , 90 , 9 , 0.9 , 90 m and 10 m. The main advantage of this divider is that it can be automatically calibrated with a calibrator and a digital multimeter. Its calibration starts from a 10 V value. It takes advantage of the DMM linearity, in particular in the 10 V range that allows improving its calibration uncertainty. After calibration, it can be used to divide DC Voltages lower than 10 V. Preliminary evaluation of its calibration uncertainties and mid-term stabilities (a week) span respectively from 1.4×106 to 6.0×104 and from 2.4×107 to 4.5×104 for ratios from 10:1 to 107:1. This divider could be involved in the calibration of nanovoltmeters in a typical range from 10 V down to 100 nV.