Report of a Multilateral Accurate Measurement Comparison on a High-Precision Multimeter to Evaluate the Traceability Transfer from INRIM in the Field of Low-Frequency Electrical Quantities

As the calibration activity of modern electrical secondary laboratories operating in the five low-frequency quantities is carried out by means of high-precision digital multimeters (DMMs), it is of fundamental importance for their correct technical surveillance through suitable inter-laboratory comparisons (ILCs). The laboratory for calibration of multifunction electrical instruments of the National Institute of Metrology Research (INRIM-Lab) provides bilateral and multilateral ILCs involving high-precision DMMs to check the measurement capabilities of electrical laboratories. In particular, this paper deals with the last multilateral ILC that INRIM-Lab provided and carried out as reference measurements’ provider to which took part twelve Italian-accredited laboratories divided into two loops. The ILC was involved in a high-precision 8.5 digit high-precision DMM to be verified in a grid of about forty measurement points. The 2σ relative uncertainties of the INRIM-Lab calibrations ranged from 1.6 × 10−6 to 1.5 × 10−4, while those of the laboratories ranged from 2.0 × 10−6 to 2.2 × 10−3. The ILC had satisfactory results confirming the correctness of both the dissemination from INRIM and the accreditation process by the Italian accreditation body for calibration laboratories.