Bilateral comparison of 10 pF and 100 pF standards (ongoing BIPM key comparisons BIPM.EM-K14.a and 14.b) between the NIMT (Thailand) and the BIPM

This report presents the results of a bilateral comparison of 10 pF and 100 pF capacitance standards between the NIMT (Thailand) and the BIPM carried out in 2018. The comparison at 10 pF forms part of the ongoing BIPM key comparison BIPM.EM-K14.a and that at 100 pF of the ongoing BIPM key comparison BIPM.EM-K14.b. The BIPM is the pilot laboratory for both of these comparisons. Two 10 pF and one 100 pF travelling standards belonging to the NIMT were used in this comparison carried out with an 'A-B-A' pattern of measurements. The standards were measured first at NIMT for a period of about one month, then for a similar period at the BIPM, and finally again at NIMT. The measurand was the two terminal-pair capacitance at a frequency of either 1000 Hz or 1592 Hz, for a measuring rms voltage of 15 V at 10 pF and 10 V at 100 pF. The results from the NIMT and the BIPM at both 1000 Hz and 1592 Hz were found to be in good agreement, with a difference smaller than the relative expanded uncertainty of the comparison.