DOCSLIB.ORG

Principles of Electrical Measurement

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Principles of Electrical Measurement PRINCIPLES OF ELECTRICAL MEASUREMENT Sensors Series Senior Series Editor: B E Jones Series Co-Editor: W B Spillman, Jr Novel Sensors and Sensing R G Jackson Hall Effect Devices, Second Edition R S Popovi´c Sensors and their Applications XII Edited by S J Prosser and E Lewis Sensors and their Applications XI Edited by K T V Grattan and S H Khan Thin Film Magnetoresistive Sensors S Tumanski Electronic Noses and Olfaction 2000 Edited by J W Gardner and K C Persaud Sensors and their Applications X Edited by N M White and A T Augousti Sensor Materials P T Moseley and J Crocker Biosensors: Microelectrochemical Devices M Lambrecht and W Sansen Current Advances in Sensors Edited by B E Jones Series in Sensors PRINCIPLES OF ELECTRICAL MEASUREMENT S Tumanski Warsaw University of Technology Warsaw, Poland New York London IP832_Discl.fm Page 1 Wednesday, November 23, 2005 1:02 PM Published in 2006 by CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2006 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10987654321 International Standard Book Number-10: 0-7503-1038-3 (Hardcover) International Standard Book Number-13: 978-0-7503-1038-3 (Hardcover) Library of Congress Card Number 2005054928 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. No part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC) 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Tumanski, Slawomir. Principles of electrical measurement / by Slawomir Tumanski. p. cm.-- (Series in sensors) Includes bibliographical references and index. ISBN 0-7503-1038-3 1. Electric measurements. 2. Electronic measurements. 3. Signal processing. I. Title. II. Sensors series. TK275.T75 2005 621.37--dc22 2005054928 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com Taylor & Francis Group and the CRC Press Web site at is the Academic Division of Informa plc. http://www.crcpress.com Contents Preface ix 1. Introduction to Measurements 1 2. Fundamentals of Electrical Measurements 13 2.1. Main Terms and Definitions 13 2.1.1. Basic terms of measurement technique 13 2.1.2. The main methods of measurements 18 2.2. Uncertainty of Measurements 26 2.2.1. Errors, uncertainty, and reliability of signal processing 26 2.2.2. Basic statistical terms and concepts 34 2.2.3. Methods of evaluation and correction of the uncertainty related to limited accuracy of measuring devices 40 2.2.4. The estimation of uncertainty in measurements 52 2.3. Standards of Electrical Quantities 57 2.3.1. Standards, etalons, calibration and validation 57 2.3.2. The standards of electrical quantities referred to the physical phenomena and laws 58 2.3.3. Material standards of electrical quantities 63 2.3.4. The reference multimeters and calibrators 69 References 71 3. Classic Electrical Measurements 73 3.1. Indicating Measuring Instruments 73 3.1.1 Electromechanical instruments versus digital measuring systems 73 3.1.2. The moving coil meters 74 3.1.3. The moving iron meters 81 3.1.4. Electrodynamic meters – wattmeters 82 3.1.5. Induction type watt-hour meters 86 3.2. Recording and Displaying Measuring Instruments 88 3.2.1. Fundamentals of oscilloscopes 88 3.2.2. Recorders and data storage devices 93 3.3. Bridge Circuits 94 3.3.1. Balanced and unbalanced bridge circuits 94 3.3.2. Null-type DC bridge circuits 96 V VI PRINCIPLES OF ELECTRICAL MEASUREMENTS 3.3.3. The AC bridge circuits 99 3.3.4. The transformer bridge circuits 104 3.3.5. The unbalanced bridge circuits 107 3.3.6. The alternatives for bridge circuits – Anderson Loop 112 3.4. Potentiometers and Comparators 114 References 118 4. Processing of the Analogue Measurement Signals 121 4.1. Signal Conditioning 121 4.1.1. Analogue measurement signals 121 4.1.2. Conditioning of resistance, capacitance and inductance 126 4.1.3. AC/DC conversion 131 4.1.4. Voltage to frequency conversion 141 4.2. Amplification of the Signals 143 4.2.1. Differential, operational and instrumentation amplifiers 143 4.2.2. Isolation amplifiers 147 4.2.3. Amplifiers of very small DC signals 150 4.2.4. Amplifiers of very small AC signals 154 4.2.5. Amplifiers of very large input resistance (electrometers) 159 4.2.6. The function amplifiers 161 4.3. Negative Feedback in the Measuring Technique 169 4.4. The Improvement of the Quality of the Analogue Signals 179 4.4.1. The noises and interferences of the analogue signals 179 4.4.2. The connection of the measuring signal to the amplifier 184 4.4.3. The analogue filtering of the signals 191 References 201 5. Digital Processing of the Measurement Signals 205 5.1. Analogue-to-Digital Converters 205 5.1.1. Sampling, quantization and coding of signals 205 5.1.2. Analogue-to-digital converters ADC 218 5.1.3. The main specifications of analogue-to-digital converters 234 5.2. Digital-to-Analogue Converters 238 5.2.1. The reconstruction of the analogue signal 238 5.2.2. The digital-to-analogue converters DAC 242 5.2.3. The main specifications of digital-to-analogue converters 247 5.3. Methods and Tools of Digital Signal Processing 249 5.3.1. The main terms of digital signal processing 249 5.3.2. The Discrete Fourier Transform DFT and Fast Fourier Transform FFT 259 5.3.3. Short-time Fourier Transform and Wavelet transform 268 5.3.4. Digital filters 275 CONTENTS VII 5.4. Examples of Application of Digital Signal Processing in Measurements 287 5.4.1. The spectral analysis 287 5.4.2. Digital signal synthesis 297 5.4.3. Improvement of the signal quality and the signal recovery 303 5.5. Digital Measuring Instruments 312 5.5.1. Digital multimeters and frequency meters 312 5.5.2. Digital oscilloscopes 318 5.5.3. Digital measurement of power and energy 323 5.6. Intelligent Data Analysis 326 5.6.1 The artificial intelligence in measurements 326 5.6.2. The adaptive filters 327 5.6.3. Artificial neural networks 331 5.6.4. Fuzzy Logic 340 References 344 6. Computer Measuring Systems 349 6.1 Introduction 349 6.2. Input Circuits of the Measuring Systems 353 6.2.1. Circuits for data conditioning and acquisition 353 6.2.2. The sensors with built-in interface – intelligent sensors 354 6.2.3. Analogue and digital transmitters 356 6.2.4. Data loggers 357 6.2.5. IEEE P1451 standard – smart sensors 359 6.3. Data Acquisition Circuits – DAQ 362 6.3.1. Plug-in data acquisition board 362 6.3.2. External data acquisition board 365 6.4. Data Communication in Computer Measuring Systems 367 6.4.1. Interfaces, buses and connectors 367 6.4.2. Serial interfaces: RS-232C and RS-485 368 6.4.3. Serial interfaces: USB and FireWire 373 6.4.4. Parallel GPIB interface (IEEE-488/IEC-625) 377 6.4.5. Wireless interfaces: IrDA, Bluetooth and WUSB 382 6.4.6. Mobile telephony systems GSM and UMTS as a tool for data transfer 385 6.4.7. Radio data acquisition and transfer 389 6.4.8. Computer systems using Ethernet and Internet 392 6.4.9. Dedicated interfaces: CAN, I2C, MicroLAN, SDI-12 396 6.4.10. HART interface and the 4 – 20 mA standard 400 6.4.11. Industrial communication standards – Fieldbus, Profibus, SCADA 401 6.4.12. Modular systems – VXI, PXI 406 6.4.13. Standard command for measuring devices – SCPI 408 VIII PRINCIPLES OF ELECTRICAL MEASUREMENTS 6.5. Measuring Systems Basing on the Signal Processors 410 6.5.1. Microcontrollers and signal processors in measuring technique 410 6.5.2. Microinterfaces – SPI and UART 418 6.6. Virtual Measuring Systems 421 6.6.1. What is the virtual measuring device? 421 6.6.2. TestPoint 424 6.6.3. Agilent VEE Pro 428 6.6.4. LabVIEW of National Instruments 431 6.7. The Examples of Computer Measuring Systems 438 6.7.1. The measuring system for testing of magnetic materials 438 6.7.2. The arbitrary wave excitation systems 442 6.7.3. The scanning device for magnetic field imaging 449 References 452 Symbols used in the Book 455 Abbreviations used in the Book 457 Index 461 Preface In libraries and bookshops we can find various books on electrical measurements1. Most of them describe various aspects of electrical measurements: digital or analogue techniques, sensors, data acquisition, data conversion, etc.
Load more

Recommended publications
  • Made to Measure. Practical Guide to Electrical Measurements in Low Voltage Switchboards V
    Contact us A 250 500 200 150 V (b) 100 (a) 50 0 t Made to measure. Practical guide to electrical measurements in low voltage switchboards A 250 500 ABB SACE The data and illustrations are not binding. We reserve 200 the right to modify the contents of this document on the 150 Una divisione di ABB S.p.A. basis of technical development of the products, 100 Apparecchi Modulari without prior notice. 50 0 Viale dell’Industria, 18 Copyright 2010 ABB. All rights reserved. - 1.500 - CAL. 20010 Vittuone (MI) Tel.: 02 9034 1 Fax: 02 9034 7609 bol.it.abb.com www.abb.com V 80 V 60 2CSC445012D0201 - 12/2010 (f) 40 50 Hz 20 0 t Made to measure. Practical guide to electrical measurements in low voltage switchboards table of Made to measure. Practical guide to electrical measurements contents in low voltage switchboards 1 Electrical measurements 5.3.2 Current transformers ......................................................... 37 5.3.3 Voltage transformers ......................................................... 38 1.1 Why is it important to measure? .......................................... 3 5.3.4 Shunts for direct current .................................................... 38 1.2 Applicational contexts .......................................................... 4 1.3 Problems connected with energy networks ......................... 4 6 The measurements 1.4 Reducing consumption ........................................................ 7 1.5 Table of charges .................................................................. 8 6.1 TRMS Measurements
    [Show full text]
  • Keithley Instrumentation for Electrochemical Test Methods and Applications ––
    Keithley Instrumentation for Electrochemical Test Methods and Applications –– APPLICATION NOTE Keithley Instrumentation for Electrochemical Test Methods and Applications APPLICATION NOTE With more than 60 years of measurement expertise, Keithley Cyclic Voltammetry Instruments is a world leader in advanced electronic test Cyclic voltammetry (CV), a type of potential sweep method, instrumentation. Our customers are scientists and engineers is the most commonly used electrochemical measurement in a wide range of research and industrial applications, technique, which typically uses a 3-electrode cell. Figure including many electrochemistry tests. Keithley manufactures 1 illustrates a typical electrochemical measurement circuit products that can source and measure current and voltage made up of an electrochemical cell, an adjustable voltage accurately. Electrochemistry disciplines that employ source (V ), an ammeter (A ), and a voltmeter (V ). The Keithley instrumentation include battery and energy storage, S M M three electrodes of the electrochemical cell are the working corrosion science, electrochemical deposition, organic electrode (WE), the reference electrode (RE), and the counter electronics, photo-electrochemistry, material research, electrode (CE). The voltage source (V ) for the potential sensors, and semiconductor materials and devices. Table 1 S scan is applied between the WE and CE. The potential (E) lists some of the test methods and applications that employ between the RE and WE is measured with the voltmeter, and Keithley products. the overall voltage (VS) is adjusted to maintain the desired Table 1. Electrochemistry test methods and applications potential at the WE with respect to the RE. The resulting Methods and Measurement current (i) flowing to or from the WE is measured with the Capabilities Applications ammeter (AM).
    [Show full text]
  • Speed Limit: How the Search for an Absolute Frame of Reference in the Universe Led to Einstein’S Equation E =Mc2 — a History of Measurements of the Speed of Light
    Journal & Proceedings of the Royal Society of New South Wales, vol. 152, part 2, 2019, pp. 216–241. ISSN 0035-9173/19/020216-26 Speed limit: how the search for an absolute frame of reference in the Universe led to Einstein’s equation 2 E =mc — a history of measurements of the speed of light John C. H. Spence ForMemRS Department of Physics, Arizona State University, Tempe AZ, USA E-mail: [email protected] Abstract This article describes one of the greatest intellectual adventures in the history of mankind — the history of measurements of the speed of light and their interpretation (Spence 2019). This led to Einstein’s theory of relativity in 1905 and its most important consequence, the idea that matter is a form of energy. His equation E=mc2 describes the energy release in the nuclear reactions which power our sun, the stars, nuclear weapons and nuclear power stations. The article is about the extraordinarily improbable connection between the search for an absolute frame of reference in the Universe (the Aether, against which to measure the speed of light), and Einstein’s most famous equation. Introduction fixed speed with respect to the Aether frame n 1900, the field of physics was in turmoil. of reference. If we consider waves running IDespite the triumphs of Newton’s laws of along a river in which there is a current, it mechanics, despite Maxwell’s great equations was understood that the waves “pick up” the leading to the discovery of radio and Boltz- speed of the current. But Michelson in 1887 mann’s work on the foundations of statistical could find no effect of the passing Aether mechanics, Lord Kelvin’s talk1 at the Royal wind on his very accurate measurements Institution in London on Friday, April 27th of the speed of light, no matter in which 1900, was titled “Nineteenth-century clouds direction he measured it, with headwind or over the dynamical theory of heat and light.” tailwind.
    [Show full text]
  • Electronic Voltmeters and Ammeters - Alessandro Ferrero, Halit Eren
    ELECTRICAL ENGINEERING – Vol. II - Electronic Voltmeters and Ammeters - Alessandro Ferrero, Halit Eren ELECTRONIC VOLTMETERS AND AMMETERS Alessandro Ferrero Dipartimento di Elettrotecnica, Politecnico di Milano, Italy Halit Eren Curtin University of Technology, Perth, Western Australia Keywords: currents, voltages, measurements, standards, analog voltmeters, digital voltmeters, microvoltmeters, oscilloscopes Contents 1. Introduction. 2. Analog Meters 2.1. DC Analog Voltmeters and Ammeters 2.2. AC Analog Voltmeters and Ammeters 2.3. True rms Analog Voltmeters 3. Digital Meters 3.1. Dual-Slope DVMs 3.2. Successive-Approximation ADCs 3.3. AC Digital Voltmeters and Ammeters 3.4. Frequency Response of AC Meters 4. Radio-Frequency Microvoltmeters 5. Vacuum-Tube Voltmeters and Oscilloscopes 5.1. Analog Oscilloscopes 5.2. Digital Storage Oscilloscopes (DSOs) 5.3. Portable Oscilloscopes 5.4. High-Voltage Oscilloscopes Appendix Glossary Bibliography Biographical Sketches Summary Voltage UNESCOand current measurements are – esse EOLSSntial parts of engineering and science. Instruments that measure voltages and currents are called voltmeters and ammeters, respectively. ThereSAMPLE are two distinct types of voltmeterCHAPTERS and ammeter, which differ from each other by the operating principle that they are based on: electromechanical instruments and electronic instruments, which also include oscilloscopes. Electromechanical voltmeters and ammeters, including thermal-type instruments, represent early technology, but still are used in many applications. Basic elements of voltages and currents from the basic physical principles have been introduced in the electromechanical voltage and current measurements section. Also, voltage and currents standards have been dealt with in detail in other articles. ©Encyclopedia of Life Support Systems (EOLSS) ELECTRICAL ENGINEERING – Vol. II - Electronic Voltmeters and Ammeters - Alessandro Ferrero, Halit Eren In this article, modern electronic voltmeters and ammeters are discussed.
    [Show full text]
  • A History of Impedance Measurements
    A History of Impedance Measurements by Henry P. Hall Preface 2 Scope 2 Acknowledgements 2 Part I. The Early Experimenters 1775-1915 3 1.1 Earliest Measurements, Dc Resistance 3 1.2 Dc to Ac, Capacitance and Inductance Measurements 6 1.3 An Abundance of Bridges 10 References, Part I 14 Part II. The First Commercial Instruments 1900-1945 16 2.1 Comment: Putting it All Together 16 2.2 Early Dc Bridges 16 2.3 Other Early Dc Instruments 20 2.4 Early Ac Bridges 21 2.5 Other Early Ac Instruments 25 References Part II 26 Part III. Electronics Comes of Age 1946-1965 28 3.1 Comment: The Post-War Boom 28 3.2 General Purpose, “RLC” or “Universal” Bridges 28 3.3 Dc Bridges 30 3.4 Precision Ac Bridges: The Transformer Ratio-Arm Bridge 32 3.5 RF Bridges 37 3.6 Special Purpose Bridges 38 3,7 Impedance Meters 39 3.8 Impedance Comparators 40 3.9 Electronics in Instruments 42 References Part III 44 Part IV. The Digital Era 1966-Present 47 4.1 Comment: Measurements in the Digital Age 47 4.2 Digital Dc Meters 47 4.3 Ac Digital Meters 48 4.4 Automatic Ac Bridges 50 4.5 Computer-Bridge Systems 52 4.6 Computers in Meters and Bridges 52 4.7 Computing Impedance Meters 53 4.8 Instruments in Use Today 55 4.9 A Long Way from Ohm 57 References Part IV 59 Appendices: A. A Transformer Equivalent Circuit 60 B. LRC or Universal Bridges 61 C. Microprocessor-Base Impedance Meters 62 A HISTORY OF IMPEDANCE MEASUREMENTS PART I.
    [Show full text]
  • A Simple Atmospheric Electrical Instrument for Educational Use
    A simple atmospheric electrical instrument for educational use A.J. Bennett1 and R.G. Harrison Department of Meteorology, The University of Reading P.O. Box 243, Earley Gate, Reading RG6 6BB, UK Abstract Electricity in the atmosphere provides an ideal topic for educational outreach in environmental science. To support this objective, a simple instrument to measure real atmospheric electrical parameters has been developed and its performance evaluated. This project compliments educational activities undertaken by the Coupling of Atmospheric Layers (CAL) European research collaboration. The new instrument is inexpensive to construct and simple to operate, readily allowing it to be used in schools as well as at the undergraduate University level. It is suited to students at a variety of different educational levels, as the results can be analysed with different levels of sophistication. Students can make measurements of the fair weather electric field and current density, thereby gaining an understanding of the electrical nature of the atmosphere. This work was stimulated by the centenary of the 1906 paper in which C.T.R. Wilson described a new apparatus to measure the electric field and conduction current density. Measurements using instruments based on the same principles continued regularly in the UK until 1979. The instrument proposed is based on the same physical principles as C.T.R. Wilson's 1906 instrument. Keywords: electrostatics; potential gradient; air-earth current density; meteorology; Submitted to Advances in Geosciences 1 E-mail: [email protected] 1 1. Introduction The phenomena of atmospheric electricity provide an ideal topic for stimulating lectures, talks and laboratory demonstrations.
    [Show full text]
  • Electrical Measurements
    Name ________________________ Group #_______ Date _________ Partners ______________________ Electrical Measurements Experimental Objective The objective of this experiment is to become familiar with some of the electrical instruments. You will gain experience by wiring a simple electrical circuit and drawing its circuit diagram. You will learn the correct use of a digital multimeter as an ohmmeter, voltmeter and ammeter. Theory Current, I, is the flow of charge, measured in amps. Voltage, V, is the difference in electrical potential between two points, measured in volts. Resistance is the ratio of voltage across to the current flowing through it, measured in ohms, Ω. V R = I Wires are conductors with very low resistance designed to carry the current from one object to another. Resistors are objects with a moderately high resistance made of carbon films. Resistors are color coded to indicate the magnitude. A circuit diagram is a diagram that represents the electrical circuit using internationally accepted symbols. The diagram represents the electrical connections of the circuit, but not necessarily the bench layout of each item. A series connection consists of two or more components that are connected end to end with one another and the same current flows through each component. A parallel connection consists of components connected so that one end of all the components are connected together and the other ends are connected together such that the same voltage is applied across each component. Multimeters are used to measure current, voltage and resistance. The meters used in our lab will give you a digital reading and since they use a battery should always be turned off when not in use.
    [Show full text]
  • An Oscillating - Magnet Watt Balance
    An Oscillating - Magnet Watt Balance H. Ahmedov TÜBİTAK, UME, National Metrology Institute of Turkey E-mail:[email protected] Abstract We establish the principles for a new generation of simplified and accurate watt balances in which an oscillating magnet generates Faraday’s voltage in a stationary coil. A force measuring system and a mechanism providing vertical movements of the magnet are completely independent in an oscillating magnet watt balance. This remarkable feature allows to establish the link between the Planck constant and a macroscopic mass by a one single experiment. Weak dependence on variations of environmental and experimental conditions, weak sensitivity to ground vibrations and temperature changes, simple force measuring procedure, small sizes and other useful features offered by the novel approach considerable reduce the complexity of the experimental setup. We formulate the oscillating-magnet watt balance principle and establish the measurement procedure for the Planck constant. We discuss the nature of oscillating-magnet watt balance uncertainties and give a brief description of the Ulusal Metroloji Enstitüsü ( UME ) watt balance apparatus. 1. Introduction In 1975 Kibble described the principles of the first moving-coil watt balance [1,2], a two-part experiment which links the electrical and mechanical Sİ units by indirect conversion of electrical power into mechanical power. The watt balance principle and macroscopic electrical quantum effects: the Josephson effect and the quantum Hall effect [3, 4] established the link between a macroscopic mass and the Planck constant, the fundamental constant of the microworld [ 5 ]. This link provides a potential route to the redefinition of the kilogram [6, 7], the last base unit which is still defined by a manmade object, the international prototype of the kilogram.
    [Show full text]
  • Experiment 0 an Introduction to the Equipment
    Experiment 0 An Introduction to the Equipment Objectives After completing Experiment 0, you should be able to: • Use basic electronic instruments • Determine the precision of a measurement • Select the scale that gives the most accurate reading • Give a qualitative description of electric potential (voltage), current, and resistance • Describe the uses of an electrometer, voltmeter, ammeter, ohmmeter, and multimeter • Use an electrometer and digital multimeter properly • Describe the precautions required to protect meters from damage. Introduction In Physics 116L, you will investigate the properties of electricity and magnetism with a variety of laboratory instruments. Unlike mechanics, for which the basic measurements of length, time, and mass are familiar, common quantities, electricity and magnetism involve unfamiliar quantities and require special instruments for their study. Some of the measurements are quite simple, for example the circuits of Experiments 5 and 6, but others are more subtle. Although you are certainly familiar with certain aspects of basic electricity -- shocks upon touching metal objects on dry days, the quantitative experiments are not trivial. You must understand a number of physical processes and phenomena to form a conceptual picture of what is happening in these experiments. We cannot explore electrostatics one step at a time as in the lectures; understanding even the simplest experiments requires the complete framework of electrostatics. These first three experiments, which introduce you to electrical instruments and the basic properties of electric charge, require considerable thought and care. If you are unfamiliar with these instruments, you may find them slightly intimidating at first. However, they are not really difficult to use. This first "experiment" is merely a set of exercises to enable you to experiment with the basic instruments and become comfortable with using them.
    [Show full text]
  • Basic Electrical Measurements
    3 Basic Electrical Measurements 3.1 Electromechanical measuring devices current is delivered to the coil by two springs – these springs are also used as the mechanisms generating There are several advantages of traditional returning torque for the pointer. electromechanical instruments: simplicity, reliability, low price. The most important advantage is that the majority of such instruments can work without any additional power supply. Since people’s eyes are sensitive to movement also this psycho-physiological aspect of analogue indicating instruments (with moving pointer) is appreciated. On the other hand, there are several drawbacks associated with electromechanical analogue indicating instruments. First of all, they do not provide output signal, thus there is a need for operator’s activity during the measurement (at least for the reading of an indicated value). Another drawback is that such instruments generally use moving mechanical parts, which are sensitive to shocks, aging or wearing out. Relatively low price of moving pointer instruments FIGURE 3.1 today is not as advantageous as earlier, because on the The example of moving coil indicating instrument (1- moving coil, 2 – market there are available also very cheap digital permanent magnet, 3 – axle, 4 – pointer, 5 – bearings, 6 – spring, 7 – correction of zero). measuring devices with virtual pointer. Regrettably, it can be stated that most of the The moving coil is placed into the gap between the electromechanical analogue instruments are rather of magnet poles and soft iron core, shaped in such a way poor quality. In most cases these instruments are not as to produce uniform magnetic field. The movement able to measure with uncertainty better than 0.5%.
    [Show full text]
  • Electrical Measurements
    ELECTRICAL MEASUREMENTS GEETHANJALI COLLEGE OF ENGINEERING AND TECHNOLOGY DEPARTMENT OF EEE Name of the Subject : Electrical Measurements JNTU CODE : 56009 Programme : UG / PG Branch: Electrical & Electronics Engineering Version No : Year: III Updated on :27/12/2014 Semester: II No. of pages : Classification status (Unrestricted / Restricted ) Distribution List : Prepared by : 1) Name : K.Mahender 1) Name : 2) Sign : 2) Sign : 3) Design : Associate Professor 3) Design : 4) Date : 27/12/2014 4) Date : Verified by : 1) Name : * For Q.C Only. 2) Sign : 1) Name : 3) Design : 2) Sign : 4) Date : 3) Design : 4) Date : Approved by : (HOD ) 1) Name : Dr. S.Radhika 2) Sign : 3) Date : SYLLABUS JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY, HYDERABAD III Year B.Tech EEE II-Semester T P C 4+1 *0 4 Unit -I Classification of measuring instruments-deflecting, controlling and damping systems, ammeters and voltmeters, PMMC,MI and MC instruments, Expression for the deflecting torque and control torque. Expression for the deflecting torque and control torque, Errors and compensation and extension of range using shunts and series resistance, Electrostatic voltmeters-electrometer type and attracted disc type. Extension of range of electrostatic voltmeters Unit-II Introduction to CT & PT- Design considerations, Ratio and phase angle errors, Types of P.F meters-dynamometer and moving iron type, I ph and 3 ph meters, Frequency meters- resonance type and Weston type, Synchroscopes Unit-III Single phase dynamometer wattmeter-LPF & UPF, Double element and three element dynamometer wattmeter, Expression for deflecting and controlling torques and extension of range of wattmeter using instrument transformers, Measurement of active in balanced systems, Measurement of reactive powers in unbalanced systems.
    [Show full text]
  • The Hall Effect C1
    The Hall Effect C1 Head of Experiment: Zulfikar Najmudin The following experiment guide is NOT intended to be a step -by-step manual for the experiment but rather provides an overall introduction to the experiment and outlines the important tasks that need to be performed in order to complete the experiment. Additional sources of documentation may need to be researched and consulted during the experiment as well as for the completion of the report. This additional documentation must be cited in the references of the report. 1 RISK ASSESSMENT AND STANDARD OPERATING PROCEDURE 1. PERSON CARRYING OUT ASSESSMENT Name Geoff Green Position Chf Lab Tech Date 18/09/08 2. DESCRIPTION OF ACTIVITY C1 Hall Effect 3. LOCATION Campus SK Building Huxley Room 403 4. HAZARD SUMMARY Accessibility X Mechanical X Manual X Hazardous Handling Substances Electrical X Other Lone Working Yes No Permit-to- Yes No Permitted? Work Required? 5. PROCEDURE PRECAUTIONS Use of 240v Mains Powered Equipment Isolate Socket using Mains Switch before unplugging or plugging in equipment Accessibility All bags/coats to be kept out of aisles and walkways. Use of Electro-magnet See attached Scheme of Work 6. EMERGENCY ACTIONS All present must be aware of the available escape routes and follow instructions in the event of an evacuation 2 THE HALL EFFECT 1. Objectives The goal of this experiment is to make accurate measurements of the charge carrier density and carrier mobility in three different materials where the majority charge carriers are electrons (n-type) or holes (p-type) using the van der Pauw method.
    [Show full text]