Standards for AC-DC Transfer

Abstract

Ac-dc transfer standards provide an essential link for the determination of ac electric quantities in terms of the SI units. Thermal converters are by far the most widely used form of primary ac-dc transfer standards. The basic principles of ac-dc transfer measurements are presented together with background to the performance and basic limitations of thermal converters as transfer standards. Developments in basic converters, voltage transfer standards and current transfer standards are reviewed, with emphasis on developments since 1985. Current activities and possible future directions are discussed.

New Thin-Film Multijunction Thermal Converter Design for Improved High-Frequency Performance

“…When using a nonannealed heater, the ac-dc difference at 10 Hz was approximately 20 V/V. When dc current passes through the heater of a thermal converter, non-Joule heating or cooling takes place in the heater due to thermoelectric effects [1]. This leads to ac-dc transfer differences caused by thermoelectric effects on the dc, referred to as frequency-independent ac-dc differences.…”

“…For example, to set it at 2 s, the size of AlN substrate can be estimated from the following equation [11]: (1) where is the heat capacity of the heat area, and is the heat conductance between the heater and the heat sink. The heat conductance can be expressed as (2) where is the input power to the TC.…”

“…T HERMAL converters are the most accurate transfer standards for realizing ac voltage standards for RMS values between ac and dc voltages [1]. This method compares the ac and dc electric power by converting the power to heat.…”

Numerical and experimental investigations of low-frequency properties of single-junction thermal converter

“…Thermal converters and thermal transfer standards are the primary means of AC voltage calibration at national measurement laboratories [1]. At low frequencies, the thermal inertia of the thermal converter is not enough to suppress the variation of the temperature.…”

Traceability of Voltage Measurements for Non-Sinusoidal Waveforms

“…Indeed, these thermal converters are widely used to trace AC quantities (AC currents and voltages) to the corresponding DC quantities with the best level of uncertainty [1]. Agreement of some parts in 10 7 to 15 part in 10 6 , in the frequency range from 1 kHz to 1 MHz, has been found between various NMIs at voltages ranging from 1 V to 3 V [2].…”