A Double Precision Arbitrary Waveform Generator Based Calibration System for Low-Value AC Resistors up to 20 kHz

In this paper we present an automated impedance bridge based on a commercial double-precision arbitrary waveform generator. The automated bridge was developed to compare impedance standards of arbitrary ratios in a full complex plane from 1 mΩ to 100Ω at frequency ranges up to 20 kHz. The expanded uncertainty of the ac-dc difference and phase angle are, respectively, less than 130 µΩ/Ω and 126 µrad up to 20 kHz for impedance ratio 1:1. The results of experimental measurements are compared with a existing system based on a sampling approach, used to calibrate AC resistors up to 20 kHz, with the objective of validate the new experimental setup and its automation.

I. Introduction

Electrical impedance play a key role in the characterization of components of various measurement systems in several industrial domains [1], as the characterization of electronic circuits [2], biological tissues and tomography in medicine [3]. The impedance (Z) is defined as the measure of the opposition of an electrical circuit to the passage of a sinusoidal alternating current (AC) at a known frequency. The calibration of electrical impedances is an important step to determine its value as a function of frequency before its use, and many calibration methods are developed and used in metrology laboratories.