The electrical DC resistance scale from 100 kΩ to 1 TΩ at IEN

At IEN, the scale of resistance in the field 100 kΩ to 1 TΩ has been revised through the characterization of a series of new standard resistors. The preliminary study, realization and characterization of four measurement methods are also described in this paper. The complete description of a new automatic method for the calibration of high-value standard resistors, particularly in the range 10 MΩ-1 TΩ, and their measurement at different voltage levels are also reported. It makes use of a programmable high-stability dc voltage calibrator which supplies a voltage V_out to the series of an unknown resistor R_x, and of a standard resistor R_s. A high-precision programmable multimeter (DMM) is used to measure V_out and the voltage Vs across the standard resistor, from which the value of the current I is determined. The value of R_x is given by R_x=(V_out-V_s)/I. The best measurement capabilities of IEN using these four measurement methods span from 0.7×10^-6 for the calibration of the 100 kΩ standard resistor at the measurement voltage of 10 V, to 7.1×10^-4 for the calibration of 1 TΩ standard resistor at the measurement voltage of 500 V.