Reference voltage divider designed to operate with oscilloscope to enable determination of ratio error and phase displacement frequency characteristics of MV voltage transformers

The effect of distorted input voltage harmonics rms values on the frequency characteristics of ratio error and phase displacement of a wideband voltage divider

Electric Power Systems Research ◽

10.1016/j.epsr.2018.10.013 ◽

2019 ◽

Vol 167 ◽

pp. 1-8 ◽

Cited By ~ 3

Author(s):

M. Kaczmarek

Keyword(s):

Voltage Divider ◽

Input Voltage ◽

Frequency Characteristics ◽

Ratio Error ◽

Phase Displacement ◽

Voltage Harmonics

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Memristors as Candidates for Replacing Digital Potentiometers in Electric Circuits

Electronics ◽

10.3390/electronics10020181 ◽

2021 ◽

Vol 10 (2) ◽

pp. 181

Author(s):

Ivo Marković ◽

Milka Potrebić ◽

Dejan Tošić

Keyword(s):

Phase Shifter ◽

Voltage Divider ◽

Frequency Characteristics ◽

Phase Shifters ◽

Pass Filter ◽

Electric Circuits ◽

Digital Potentiometer ◽

Memristive Circuits ◽

Parasitic Effects ◽

Additional Level

Digital potentiometers are substantial components for the design of many mixed-signal electronic circuits and systems. Their capability to program resistance value almost instantly provides hardware designers an additional level of freedom. Unfortunately, this feature is limited to DC and lower frequencies, due to parasitic effects. Nowadays, memristors as continuously tunable resistors are becoming candidates for potentiometer successors. Memristors are two-terminal non-volatile devices which have less significant parasitic effects and a wide resistance range. The memristance value can be changed on the fly. Using nanotechnology, memristor implementation has a nanoscale footprint with nanosecond transition between resistive states. In this paper, we present a comparison between the frequency characteristics of digital potentiometers and the only commercially available memristors. Memristor parasitic effects dominate at higher frequencies which extends the bandwidth. In order to present the advantages of memristive circuits, we have analyzed and implemented tunable circuits such as a voltage divider, an inverting amplifier, a high-pass filter, and a phase shifter. A commercially available memristor by KnowM Inc. is used for this purpose. Experimental results obtained by the measurements verify that a memristor has equal or better characteristics than a digital potentiometer. Memristive realizations of voltage dividers and inverting amplifiers have a wider bandwidth, while filters and phase shifters with a memristor have almost identical frequency characteristics as the corresponding realizations with a digital potentiometer.

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Optimised calibration programmes for comparators for instrument transformers

tm - Technisches Messen ◽

10.1515/teme-2020-0086 ◽

2021 ◽

Vol 88 (2) ◽

pp. 122-131

Author(s):

Christian Mester

Keyword(s):

Experimental Study ◽

Operating Principle ◽

Device Under Test ◽

Operating Range ◽

Ratio Error ◽

Phase Displacement ◽

Instrument Transformers ◽

Instrument Transformer ◽

Method Of Measurement

Abstract Traditionally, instrument transformers are calibrated using bridges. By definition, bridges use the null method of measurement. The traditional calibration programme for instrument transformer bridges characterise namely this null measurement. Many new commercial comparators for instrument transformer use a very different method. They sample the secondary signals of reference and device under test (dut) transformer independently. Based on the samples, magnitude and phase of both signals are determined. Ratio error and phase displacement are calculated. Consequently, the significance of their calibration using the traditional calibration programme is limited. Moreover, the operating range of modern comparators is much larger than that of bridges. The additional versatility cannot be used without an adapted calibration programme. This article analyses the calibration programmes for both technologies. An experimental study confirms both the suitability of the new calibration programme and the need to chose the calibration programme depending on the technology of the device to be calibrated. The conclusion is very general and applies to all measurement problems where an operating principle is replaced by another – when changing the operating principle, it is important to check the calibration programme and adapt it if necessary.

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