[296880] Artigo – SEMETRO – Congresso Internacional de Metrologia Mecânica

Resumo: With the SI redefinition, back in May 20th, 2019, any method capable of deriving a SI base quantity value traceable to the set of seven reference constants, could be used to realize their respective SI unit (stricto sensu realization). This is the case of the volt realized through Josephson Voltage Standards (JVS). Although such systems are widely used for dc voltage sources and meters calibration, their application in ac voltage calibrations still have some limitations (in amplitude range, frequency range, etc.). Hence, Thermal Converters (TC) still play an important role in the AC voltage calibration field. However, TC calibration is not directly linked to the new SI fundamental constants, which could be provided by JVS. Such primary standards, on the other hand, do not provide currents big enough for Thermal Converters calibration (for instance, 7.5 mA, as it is the case of Planar Multijunction Thermal Converters – PMJTC – with 400 Ω of input resistance and 3 V maximum input voltage). Hence, we developed an impedance matching circuit, for coupling of PMJTC to Programmable Josephson Voltage Standards (PJVS), aiming to establish a link between the Josephson AC primary standard voltage system and the AC-DC transfer standard. We investigated potential operational amplifiers proper for such applications and four integrated circuits were chosen. Among the topologies previously studied, simulations and assembly of impedance matching circuits prototypes were made, and the one that behaved best in the required function presented an approximate average error of -1.51 μV and Type A uncertainty of 0.07 μV/V.