Abstract
A set of fixed points maintained by national metrology institutes (NMIs) for calibrating platinum resistance thermometers (PRTs) in Canada (National Research Council, NRC), Argentina (Instituto Nacional de Tecnologia Industrial, INTI) and Brazil (Instituto Nacional de Metrologia, Normalizaçãoe Qualidade Industrial, INMETRO) were compared using two methods. A set of portable cells was used in one method, and in the other a calibrated PRT. The fixed-point differences were as follows. For the INTI the differences ΔT = T(INTI) − T(NRC) found at the Ag, Al, Zn, Sn, In, Ga and Hg points were 3.5 mK, 2.8 mK, 1.8 mK, −0.5 mK, 0.2 mK, −0.2 mK and −0.5 mK, respectively. For the INMETRO the differences ΔT = T(INMETRO) − T(NRC) at the above fixed points are 0.7 mK, 3.3 mK, −1.3 mK, −1.9 mK, −0.3 mK, −0.1 mK, −0.4 mK, respectively, and 0.8 mK at the Ar point.