Frequency-dependent component of AC-DC transfer difference of a redesigned calorimetric thermal converter

This article presents an analysis of the frequency-dependent component of the AC-DC transfer difference of a calorimetric thermal voltage converter (CTVC) with substantially reduced DC reversal error. It contains an analysis of the effect of this reduction on the AC-DC transfer difference. The analysis was based on the mathematical model of a CTVC waveguide, which was extended by estimation of the residual parameters of the CTVC heater (microwave rod resistor) using the finite element method (FEM). The results of the analysis were validated by laboratory measurements. The article also contains the uncertainty budget of the AC-DC transfer difference of the new CTVC. Despite its high thermal time constant, the CTVC is currently one of the most accurate AC voltage standards in the frequency range from 1 to 100 MHz.