Automated precision DC voltage fixed ratios divider

At the National Institute of Metrological Research (INRIM), an automated precision DC voltage fixed-ratios divider allowing the division ratios 10:1 and 100:1 has been built. It is made utilizing one hundred selected bulk metal foils 10 kΩ resistors with low temperature coefficient. Being the instrument inter-connectable to a multi-meter (DMM) characterized in linearity on the 10 V range and to a DC voltage generator, it can be quickly and automatically calibrated when necessary. This calibration method has been validated by comparing it with another method involving the INRIM DC voltage ratio standard. Other achievement is that the characterization of the linearity of the DMM on the 10 V range allow considering in the uncertainties budget of the calibration of the divider, the uncertainties of the linearity characterization of the DMM instead of its much larger accuracy specifications. The expanded uncertainties of the calibration of the 10:1 and 100:1 ratios are respectively 4.6 × 10−7 and 6.6 × 10−7, suitable to employ the divider in an automated measurement setup with a DMM and a DC voltage standard to calibrate DC voltage generators as top-level calibrators, widespread in secondary electrical laboratories.