Characterization of a precision modular sinewave generator

Abstract

At the Czech Metrology Institute (CMI) we have developed a precision modular sinewave generator for impedance ratio bridges. The generator was developed to improve previously available designs regarding amplitude and phase accuracy, linearity, absolute stability, stability of the ratio between two outputs and harmonic distortion. It generates up to 7 Vrms in a frequency range from 1 mHz up to 20 kHz, extendable to 100 kHz with small changes to the filters. The amplitude resolution is better than 0.01 μV V−1 of full scale with an output voltage stability of 0.05 μV V−1/30 min and a stability for the ratio between two outputs of 0.02 × 10−6 over several hours. The generator can be powered from internal batteries and is controlled via optically isolated connections. The internal clock and voltage references can be replaced by external ones, optically coupled in the case of the clock. In this paper, we discuss experimental results obtained with the generator used as a signal source in digital impedance bridges with relative combined uncertainties from 10–5 down to 10–8. The generators have been used in a bridge to drive a quantum Hall resistor in the AC regime. The use of a generator with an AC quantum voltmeter will also be discussed. The generator is not only applicable in the field of AC impedance metrology but also for on-site comparisons of AC quantum voltage standards or, in general, where there is a need for precision voltage sources.

A Comprehensive Analysis of Error Sources in Electronic Fully Digital Impedance Bridges

“…The ports DHP1 and DHP2 are connected to the 3 Digital signal generators employed in digital bridges can be based either on direct digital synthesizers (DDSs) with phase accumulation (e.g. [22]) or on synthesizers with variable sample rate (e.g. [23]).…”

Fluke 8588A and Keysight 3458A DMM Sampling Performance

“…R. Lapuh is with the Metrology Institute of the Republic of Slovenia, 3000 Celje, Slovenia, (e-mail: rado.lapuh@gov.si). Jan Kučera and Jakub Kováč are with Czech Metrology Institute (CMI), Okružni 31, 638 00 Brno, Czech Republic B. Voljč is with Slovenian Institute of Quality and Metrology, A precision ČMI SWG03 DDS source [10] and Keysight 33622A arbitrary waveform synthesizer [11] were used for all measurements requiring a sine wave input signal.…”

Comparison of a 100-pF Capacitor With a 12 906-Ω Resistor Using a Digital Impedance Bridge

“…The latter still provide measurements with the highest accuracy for the most demanding applications, including the realization of the capacitance unit from calculable capacitors or the ac quantized Hall resistance (QHR) through a quadrature bridge [2][3][4]. However, the digital bridges have been noticeably improving for impedance comparisons, offering many advantages through computer control and automation [5][6][7][8][9][10][11]. In particular, Josephson arbitrary waveform synthesizers establish a quantum-based voltage ratio standard that can be used for impedance comparisons at any phase angle [5,6].…”

“…Digital signal sources custom-designed for impedance bridges have also shown great promise. A dual-channel ac voltage source with amplitude ratio stability better than 0.01 μV/V and a phase resolution of 0.2 µrad at 1 kHz has been reported [10]. A fully-digital four-terminal-pair (4TP) bridge, using such a custom-designed voltage ratio source for reference, has been reported for RC comparisons with a 1:1 magnitude ratio with a combined uncertainty of 9.2×10 −8 , showing great promise for the realization of the unit of capacitance from an ac QHR standard [11].…”

“…Another interesting approach [12] is to use commercial synthesizers that are then stabilized with a negative feedback loop, minimizing the bridge error signal. When the voltage ratio of two synthesized sources is used directly as the reference for impedance ratio measurements, as described in the literature [5][6][7][8][9][10][11], the stability of the voltage ratio can become a major limiting factor for the overall bridge performance. It appears that an underexplored research area is to mimic in the digital domains some analog techniques that are commonly used in the analog bridges to correlate and combine detector voltages, enabling suppression of the effect of source fluctuations.…”