Evaluation of uncertainty in AC voltage measurement using a digital voltmeter and Swerlein's algorithm

A model is proposed for a sampling algorithm that uses a high-resolution voltmeter for measuring the RMS value of a sinusoidal voltage waveform. The uncertainty associated with the result of measurement is evaluated according to the rules in the ISO/BIPM guide to the expression of uncertainty in measurement. The standard uncertainty was evaluated to be less than 5/spl times/10/sup -6/ in the 1-1000 V and 1-100 Hz ranges. The uncertainty contribution associated with the conditioner and amplifier frequency response correction is dominant in the high frequency range.

Introduction

About ten years have passed since the introduction of the Swerlein's algorithm. It was developed for the accurate measurement of RMS voltage at low frequencies using an HP 3458A digital voltmeter^1.

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[1]. The algorithm has been exhaustively tested. Differences of less than 1.2.10⁻⁶between it and a multi-junction thermal converter were reported for voltages in the 10-V range and frequencies in the 10–100 Hz range [2]. Differences of less than 10.10⁻⁶were also reported for voltages in the range 0.2–20 V and frequencies up to 1 kHz [3]. The algorithm has been extensively used as a standard in industry.