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 1.4×106 to 6.0×104 and from 2.4×107 to 4.5×104 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