A reevaluation of the NIST low-frequency standards for AC-DC difference in the voltage range 0.6-100 V

A reevaluation of the NIST standards of ac-dc difference was undertaken in an effort to reduce the calibration uncertainty offered by NIST for thermal voltage converters (TVC's) at frequencies below 100 Hz. This paper describes the measurements taken in support of this effort, as well as the devices used for the reevaluation process and the analysis of the uncertainty of the measurements. This reevaluation of the NIST low-frequency standards will permit a significant reduction in uncertainty for ac-dc difference calibrations at 10 Hz in the voltage range from 0.6-100 V.