INTRO

PUBLIKACJE KSIAZKI DYDAKTYKA REDAKCJA PE DOKTORANCI ENGLISH

INSTITUTE OF PHYSICS

SERIES ON SENSORS

THIN FILM MAGNETORESISTIVE SENSORS

ISBN 0 7503 0702 1

IOP Publishing Ltd. 2001

Bristol and Philadelphia

CONTENTS         

 1             AMR SENSORS

1.1  Anisotropic magnetoresistive effect in thin ferromagnetic films                                  1

1.1.1. Essential information about the magnetoresistive effects                                       1

1.1.2. The origin of anisotropic magnetoresistance in ferromagnetic metals                8

1.1.3. The theory of magnetoresistance in ferromagnetic metals                                  12

1.1.4. Thin ferromagnetic film as the magnetic field sensor                                            17

1.1.5. Applying the Stoner-Wohlfarth model for analysis of
           magnetoresistive effects                                                                                                     22
 

1.2.     Biasing and stabilizing techniques                                                                                   27

1.2.1. The biasing and stabilizing fields in ferromagnetic
                 magnetoresistors                                                                                                            27

1.2.2. The real thin film – the multidomain structure and the

          dispersion of anisotropy                                                                                                       33

1.2.3. The sensors biased by the hard magnetic layer                                                    45

1.2.4. The sensors biased by the current conducting layer                                             52

1.2.5. Biasing by exchange coupled antiferromagnetic layer                                          58

1.2.6. The soft adjacent layers (SAL) biasing technique                                                  63

1.2.7. Dual element sensors                                                                                                 70

1.2.8. AC biasing techniques                                                                                                76

1.2.9. The reverse mode of biasing                                                                                     81 

1.3.  Design and performances of AMR sensors                                                                    83

1.3.1. The influence of the sample geometry on the MR effect                                       83

1.3.2. The influence of magnetization non-uniformity on the MR effect                         89

1.3.3. Technological factors affecting the performances of AMR sensors                   97

1.3.4. The design and construction of AMR sensors                                                     115

1.3.5. The performances of AMR sensors                                                                       132

1.4. References                                                                                                                             159

 

2.            GMR SENSORS  

2.1.  Giant magnetoresistive effects                                                                                         165

2.1.1. An historical review and the main terms                                                                 165

2.1.2  Oscillatory exchange coupling in the magnetic multilayers                                173

2.1.3. Other coupling effects in multilayer structures                                                      185

2.1.4. Theoretical models of giant magnetoresistance                                                  191

2.1.5. Ferromagnetic multialayers as magnetic field sensors                                      199 

2.2.  Various types of GMR structures                                                                                      209

2.2.1. Structures with aniferromagnetic coupling                                                             209

2.2.2. Granular GMR structures                                                                                            217

2.2.3. Spin valve structures with asymmetric magnetic layers

          (uncoupled structures)                                                                                                 222

2.2.4. Spin valve structures with exchange biased layer                                                 229

2.2.5. Current perpendicular to plane (CPP) structures                                                  241

2.2.6. Magnetic tunnel junction (MTJ) structures                                                               247

2.2.7. Colossal magnetoresistance (CMR) thin film structures                                     251

2.2.8. Giant magnetoimpedance (GMI) structures                                                            256 

2.3.  Preparation, design and performances of GMR sensors                                            260

2.3.1. The deposition of thin film GMR structures                                                             260

2.3.2. Technological factors affecting the performances of

 GMR sensors                                                                                                               266

2.3.3. The shape effects in thin film GMR devices                                                            276

2.3.2. Design and construction of GMR sensors                                                              286

2.4.  References                                                                                                                              299

 

3. APPLICATIONS OF THE MAGNETORESISTIVE SENSORS 

3.1. Magnetic measurements                                                                                                     325

3.1.1. Magnetometers and compasses                                                                             325

3.1.2 Gradiometers, magnetic anomaly detection                                                           336 

3.2. Electrical measurements                                                                                                    341

3.3. Current transducers                                                                                                       341

3.4. Electrical transducers, switching and logic elements                                             347 

3.3. Magnetoresistive elements in data storage applications                                            353

3.3.1. Magnetic Random Access Memory (MRAM) devices                                            353

3.3.2. Magnetic card readers                                                                                                357

3.3.3. Magnetoresistive heads for tapes and discs applications                                  361

3.3.4. Unshielded magnetoresistive reading heads                                                       372

3.3.5. Shielded magnetoresistive heads                                                                           376

3.3.6. Yoke-type magnetoresistive heads                                                                          382 

3.4. Transducers of mechanical values                                                                                   384

3.4.1. Transducers of linear displacement                                                                        384

3.4.2. Transducers of angular position                                                                               391

3.4.3. Measurements of rotational speed                                                                          396 

3.5. Material testing and magnetic field imaging                                                                   400

3.5.1. Material testing by means of thin film magnetoresistors                                     400

3.5.2. Magnetic imaging systems                                                                                        406

3.6. References                                                                                                                               417 

List of Symbols                                                                                                                               431

List of Abbreviations                                                                                                                      433

Index                                                                                                                                                  435

 

WYDAWNICTWO NAUKOWO-TECHNICZNE

TECHNIKA POMIAROWA

ISBN 83-204-3233-2

WNT 2006

Warszawa

SPIS TREŚCI         

1        WPROWADZENIE DO MIERNICTWA ELEKTRYCZNEGO                                               19

 

2           PODSTAWY MIERNICTWA ELEKTRYCZNEGO

2.1.  Podstawowe pojęcia miernictwa elektrycznego                                                                31

2.2. Główne metody pomiarowe                                                                                                    33

2.3. Podstawy teorii błędów i niepewności pomiarów                                                              39

2.3.1. Błąd, dokładność, niepewność wyniku pomiaru                                                     39

2.3.2. Podstawowe wiadomości z rachunku prawdopodobieństwa                              44

2.3.3. Metody oszacowania i wstępnej eliminacji składowych błędu pomiaru            48

2.3.4. Określanie niepewności pomiaru                                                                              58

2.4. Wzorce jednostek elektrycznych                                                                                             63

        2.4.1. Wzorce, etalony, kalibratory                                                                                          63

2.4.2. Wzorce elektryczne oparte na definicji zjawiska fizycznego                                   63

2.4.3. Materialne wzorce wielkości elektrycznych                                                               68

2.4.4. Multimetry wzorcowe i kalibratory                                                                                74

 

3            MIERNICTWO KLASYCZNE  

3.1. Elektromechaniczne przyrządy pomiarowe                                                                         77

       3.1.1. Przyrządy elektromechaniczne czy przyrządy cyfrowe?                                            77

       3.1.2. Mierniki magnetoelektryczne                                                                                       78

       3.1.3. Mierniki elektromagnetyczne                                                                                       84

       3.1.4. Watomierze elektrodynamiczne                                                                                  85

       3.1.5. Liczniki indukcyjne                                                                                                         89  

3.2. Przyrządy rejestrujące                                                                                                              91

       3.2.1. Podstawy techniki oscyloskopowej                                                                            91

       3.2.2. Rejestratory                                                                                                                     97

3.3. Układy mostkowe                                                                                                                     98

        3.3.1. Układy mostkowe zrównoważone i niezrównoważone                                        100

        3.3.2. Układy mostkowe prądu stałego                                                                             102

        3.3.3. Układy mostkowe prądu przemiennego                                                                 108

        3.3.4. Mostki transformatorowe                                                                                           110

        3.3.5. Układy mostkowe niezrównoważone                                                                      116

        3.3.6. Układy alternatywne dla układów mostkowych, pętla Andersona                     117

3.4. Układy kompensacyjne i komparacyjne                                                                            117

        3.4.1. Układy kompensacyjne                                                                                              117

        3.4.2. Układy komparacyjne                                                                                                 118

 

4           ANALOGOWE PRZETWARZANIE SYGNAŁÓW POMIAROWYCH

4.1. Sygnały pomiarowe i ich przetwarzanie                                                                              123

4.2. Kondycjonowanie rezystancji, pojemności i indukcyjności                                            127

4.3. Przetwarzanie AC/DC                                                                                                             133

4.4. Przetwarzanie napięcia na częstotliwość                                                                           141

4.5. Wzmacnianie sygnałów                                                                                                         143

        4.5.1. Wzmacniacze różnicowe, operacyjne i instrumentalne                                        143

        4.5.2. Wzmacniacze izolujące                                                                                               146

        4.5.3. Wzmacniacze bardzo małych napięć stałych (autozero)                                      149

        4.5.4. Wzmacniacze bardzo małych napięć przemiennych (homodynowe)                153

        4.5.5. Wzmacniacze o wielkiej rezystancji wejściowej (elektrometry)                          157

        4.5.6. Wzmacniacze realizujące funkcje matematyczne                                                 159

4.6. Sprzężenie zwrotne w przetwornikach pomiarowych                                                       165

4.7. Poprawa jakości przetwarzania sygnału analogowego                                                  174

        4.7.1. Szumy i zakłócenia sygnału                                                                                       174

        4.7.2. Przesyłanie sygnału do wzmacniacza – przewody doprowadzające                 178           

        4.7.3. Analogowa filtracja sygnału                                                                                       184

 

5        CYFROWE PRZETWARZANIE SYGNAŁÓW POMIAROWYCH

5.1. Przetworniki analogowo-cyfrowe                                                                                          195

       5.1.1. Próbkowanie, kwantowanie i kodowanie sygnałów                                              195

       5.1.2. Rodzaje przetworników analogowo-cyfrowych                                                        205

       5.1.3. Parametry opisujące właściwości przetworników analogowo-cyfrowych          220

5.2. Przetworniki cyfrowo-analogowe                                                                                          223

       5.2.1. Rekonstrukcja sygnału analogowego                                                                      223

       5.2.2. Rodzaje przetworników cyfrowo-analogowych                                                        226

       5.2.3. Parametry opisujące właściwości przetworników cyfrowo-analogowych          230

5.3. Narzędzia cyfrowego przetwarzania sygnałów pomiarowych                                         232

       5.3.1. Podstawowe pojęcia teorii cyfrowego przetwarzania sygnałów                          232

       5.3.2. Dyskretna transformata Fouriera (DFT) i szybka transformata Fouriera (FFT) 240

       5.3.3. Analiza czasowo-częstotliwościowa sygnałów – transformata falkowa             248

       5.3.4. Filtry cyfrowe                                                                                                                   253

5.4. Przykłady wykorzystania cyfrowego przetwarzania sygnałów pomiarowych                 267

       5.4.1. Analiza widmowa                                                                                                           267

       5.4.2. Cyfrowa synteza sygnałów                                                                                           276

       5.4.3. Odzyskiwanie sygnału cyfrowego – poprawa jego jakości                                    281

       5.4.4. Cyfrowe przyrządy pomiarowe                                                                                     289

       5.4.5. Oscyloskopy cyfrowe                                                                                                     295

       5.4.6. Cyfrowe przetwarzanie mocy i energii                                                                        299

5.5. Narzędzia sztucznej inteligencji w przetwarzaniu sygnałów pomiarowych                   301

       5.5.1. Co to jest sztuczna inteligencja?                                                                                301

       5.5.2.Filtry adaptacyjne                                                                                                            302

       5.5.3. Sztuczne sieci neuronowe                                                                                           305

       5.5.4. Systemy logiki rozmytej                                                                                                 312

 

6       KOMPUTEROWE SYSTEMY POMIAROWE

6.1. Wiadomości ogólne                                                                                                                319

6.2. Obwody wejściowe systemów pomiarowych                                                                     323

        6.2.1. Obwody kondycjonowania i zbierania danych                                                         323

        6.2.2. Czujniki z wbudowanym interfejsem – czujniki inteligentne                                 324

        6.2.3. Nadajniki analogowe i cyfrowe                                                                                   325

        6.2.4. Układy rejestratorów danych do zdalnego poboru sygnałów z czujników          327

        6.2.5. Czujniki inteligentne – standard IEEE P1451                                                          329

6.3. Układy zbierania danych – karta pomiarowa (DAQ)                                                           333

6.4. Układy komunikacji i transmisji danych                                                                               337

        6.4.1. Interfejsy, magistrale, złącza                                                                                        337

        6.4.2. Interfejsy szeregowe RS-232C i RS-485                                                                   338

        6.4.3. Interfejsy szeregowe USB oraz FireWire (IEEE-1394)                                            343

        6.4.4. Interfejs równoległy GPIB (IEEE-488/IEC-625)                                                         346

        6.4.5. Interfejsy komunikacji bezprzewodowej: IrDA, Bluetooth, WUSB                          351

        6.4.6. Telefonia komórkowa GSM i UMTS jako narzędzie transmisji danych                354

        6.4.7. Komunikacja radiowa w systemie przesyłania danych                                          358                                                

        6.4.8. Sieciowe systemy pomiarowe – Ethernet                                                                 361

        6.4.9. Wykorzystanie sieci energetycznych do przesyłania informacji – PLC                364

        6.4.10. Interfejs HART i standard 4-20 mA                                                                          365

        6.4.11. Interfejsy specjalizowane: CAN, I2C, MicroLAN, SDI-12                                      367

        6.4.12. Systemy modułowe: VXI, PXI                                                                                     371

        6.4.13. Magistrale przemysłowe: FieldBus, ProfiBus, Industrial IT                                 373

        6.4.14. Uniwersalny język programowania przyrządów pomiarowych – SCPI              377

6.5. Wykorzystanie mikrokontrolerów w systemach pomiarowych – mikrosystemy

       pomiarowe                                                                                                                                  379

       6.5.1. Procesory sygnałowe i mikrokontrolery w technice pomiarowej                           379

       6.5.2. Mikrointerfejsy: SPI i UART                                                                                            389

6.6. Wirtualne przyrządy pomiarowe                                                                                              392

       6.6.1. Co to jest wirtualny przyrząd pomiarowy?                                                                   392

       6.6.2. TestPoint                                                                                                                           394

       6.6.3. Agilent VEE Pro                                                                                                                399

       6.6.4. Pakiet programowy LabView                                                                                         401

6.7. Przykłady komputerowych systemów pomiarowych                                                           408

       6.7.1. Komputerowy system pomiarowy do badania materiałów magnetycznych        408

       6.7.2. System komputerowy do wymuszania zadanego kształtu sygnału

        magnesującego                                                                                                                        411

       6.7.3. Komputerowy system pomiarowy do skanowania pól magnetycznych               415   

 

 

TAYLOR&FRANCIS

SERIES ON SENSORS

PRINCIPLES OF ELECTRICAL MEASUREMENTS

ISBN 0 7503 1038 3

CRC Press 2006

New York, London

CONTENTS 

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

      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

 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

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