10 V, 1 Ω, 10 kΩ high accuracy standard setup for calibration of multifunction electrical instruments and for inter-laboratory comparisons

A temperature controlled 10 V, 1Ω and 10 kΩ transportable setup has been developed at National Institute of Metrological Research (INRIM) for the calibration and adjustment of multifunction electrical instruments as digital multimeters (DMMs) and multifunction calibrators (MFCs) and for high level inter-comparisons. The Resistance Standards are made of two 10 Ω and 100 kΩ resistors nets connected in parallel while the 10 V Standard is an ultra-low noise-drift based reference INRIM developed circuit. The project of the setup started from a previous realization revisiting it and adding a 10 V Standard. The resistors net of the 1 Ω is inserted in oil-bath along with the internal side of its connectors lowering the thermo-electromotive forces (emfs). The three Standards are further enclosed in a thermo-regulated copper enclosure and in an external aluminium case. The setup is also equipped with a high insulation switch to select the desired Standard. Preliminary results (3 h relative stabilities ranging from 5×10−8 to 7×10−8) and temperature coefficients are satisfactory to the scope of the realization.