Stability evaluation of 1 Ω and 10 kΩ standard resistors using a step-down method

The traceability chain of electrical resistance in Brazil relies upon standard resistors of 1 Ω and 10 kΩ maintained by the Electrical Standardization Metrology Laboratory (Lampe) at the National Institute of Metrology, Quality and Technology (INMETRO), the country’s national metrology institute. These standard resistors are periodically calibrated at the Bureau International des Poids et Mesures (BIPM) in France to ensure traceability to the International System of Units (SI). Transport can influence the properties of the resistors and change their values. Lampe checks resistors’ changes before and after calibration at the BIPM. The highest differences tend to occur with the 1 Ω resistors. However, drift rate evaluation becomes arduous when the check results show slight changes in the values – of about 0.10 μΩ Ω−1 – due to the uncertainty components involved. In this work, the step-down is a procedure to measure the 1 Ω resistors through a 10 kΩ resistor. The comparison of results between Lampe and INMETRO’s Quantum Electrical Metrology Laboratory (Lameq) shows a relative difference of less than 0.07 μΩ Ω−1. The results agreement allowed Lampe to confidently use the step-down method to evaluate 1 Ω resistors’ drift.