Low voltage AC-DC transfer standards at LNE
This paper describes the method used to establish the traceability of LNE AC-DC transfer standards in the mV-range to the 1 V multijunction converter, which serves as the primary AC-DC standard. Main uncertainty components are listed and final uncertainty given for the different voltage levels. An independent method was developed for the calibration of thermal converters at 0.3 V and 0.2 V. The agreement between this method and the step-down is within the standard uncertainty.
Recharacterization of thermal voltage converters after thermoelement replacement
This paper describes the relationship between the characteristics of various thermoelements (TE's) as voltage or ourrent converters and the overall ac-dc differences of a voltage range. An algorithm is presented to predict the ac-dc differences of series resistors with different TE's, and a method for recharacterizing a thermal voltage converter containing a replacement TE is given. The measured results show that for most applications, a complete recharacterization of the TVC set is unnecessary.
Components and Systems for AC/DC Transfer at the ppm Level
Development of new null detectors and the advent of cheap computer power have brought improvements in ac/dc transfer measurements. It has been found that almost all commercial resistors show anomalous frequency responses at high voltages. Techniques for the selection of the best devices and new resistor mountings are described.