Calibration: Philosophy in Practice

Calibration: Philosophy in Practice

Second Edition

FLUKE

Contents:

Section One: Introduction Chapter 1: About This Book 1-1 Which Parts of This Book Should You Read? 1-3

People New to Metrology 1-3

Experienced Metrologists 1-3 Laboratory Managers 1-3

What Are the Sections About? 1-4 Conventions Used in This Book 1-5

Chapter 2: The Romance of Metrology 2-1

Section Two: Universal Elements of Metrology Chapter 3: Metrology: A Brief Overview 3-1

What Is Metrology? 3-3 What Metrology Means 3-3 What People Need to Know About Metrology 3-3 Who or What Controls Metrology? 3-3 Who Does Metrology? 3-4 Calibration—What Is It? 3-4 Where Are Metrology and Calibration Done? 3-4

Primary Laboratories 3-4

Secondary Laboratories 3-4 Research Laboratories 3-4 Calibration Laboratories 3-4

Mobile Laboratories 3-5 What Does the Metrology Process Involve? 3-5 Standard Units and Measurement Standards 3-5

Traceability 3-5 Common Metrology Terms 3-6

Chapter 4: International Metrology 4-1 The Modern Metric System 4-3

The System of Units 4-3

Base Units 4-3 The SI and Science 4-4 Supplementary Units 4-4

Derived Units 4-4

Contents

Multiplication Factors 4-5

Other Systems of Units 4-5

Constants of Nature 4-5

National Laboratories 4-6

International Metrology Organizations 4-6

Physical Standards Organization 4-6

Non-Treaty Organization 4-7

ANSI's Role 4-8

Technical and Professional Societies 4-9

U.S. Standards-Writing Organizations 4-9

Other U.S. Organizations 4-9

Key References 4-10

Chapter 5: Basic D C and Low Frequency Metrology 5-1

Measurement Units 5-3

Coherent, Uniform and Unified 5-3

Defined, Realized and Represented 5-3

Disseminated and Extended 5-4

Measurement Equipment 5-4

Types of Measurement Equipment 5-4

Principles of Operation 5-5

Imperfections in Equipment and

Test Configurations 5-6

Types of Measurements 5-9

Direct Measurements 5-9

Differential Measurements 5-9

Transfer Measurements 5-9

Ratio Measurements 5-10

Indirect Measurements 5-10

Calibration Measurements 5-10

Types of Calibration Measurements 5-10

Examples of Calibration Measurements 5-10

Reports of Calibration Measurements 5-11

Measurement Uncertainty 5-11

Measurement Error 5-11

Expressing Uncertainty 5-12

Key References 5-13

Chapter 6: Standards and Traceability 6-1

Traceability and the National Measurement System . . . 6-3

Why Measurements Must Be Traceable 6-4

What Is Involved in a Traceable Calibration? 6-4

Standards 6-5

The Ideal Standard 6-5

Standards for Your Measurements 6-5

Traceability 6-6

Establishing And Maintaining Traceability 6-6

Maintaining a Local Standard 6-8

Less Rigorous Methods for Maintaining

Traceability 6-8

Measurement Services Providing Traceability 6-9

National Measurement Services 6-9

Commercial Measurement Services 6-9

Measurement Assurance Programs (MAPs) 6-10

Reverse MAPs 6-10

The FLUKE DVMP 6-10

Reports 6-11

Proving Traceability 6-11

Documenting Calibration Results 6-11

Managing the Workload 6-11

Improving the Calibration Activity 6-12

Notifying Users 6-12

Key References 6-12

Section Three: Primary and Secondary Standards Chapter 7: Direct Voltage and Current 7-1

SI Definitions of DC Current and Voltage 7-3

The Ampere 7-3

The Volt 7-3

Direct Voltage Representations 7-4

Josephson-Effect Intrinsic Standard 7-4

A Closer Look at the Josephson Junction 7-5

Who Needs a Josephson Array 7-7

Solid-State DC Voltage Standards 7-8

Saturated Standard Cells 7-12

Extending Voltage Values 7-15

Ratio Techniques 7-15

Working Standards 7-16

DC Current 7-16

Hookup Considerations 7-16

DC Lore 7-17

Saturated vs. Unsaturated Weston Cells 7-17

History of Standard Cells 7-17

NBS Maintenance Of The Volt 7-17

Comparison Of Voltage Standards 7-17

Key References 7-18

Chapter 8: D C Resistance 8-1

SI Definition of DC Resistance (the Ohm) 8-3

Contents

Resistance Representations 8-3

Quantum Hall Effect Intrinsic Standard 8-3

A Closer Look at the Quantum Hall Effect

Intrinsic Standard 8-3

Thomas One Ohm Standard 8-5

Reichsanstalt Artifact Standard 8-5

Rosa Artifact Standard 8-5

ESISR104 8-5

Maintenance of Resistance Standards 8-6

Intercomparing Resistors 8-6

Extending Resistance Values 8-8

Ratio Techniques 8-8

Working Standards 8-9

Fluke 742A 8-10

Fluke DMM Calibration Standards 8-10


Resistance Lore 8-10

History Of Resistance Standards 8-10

NIST Maintenance of the Ohm 8-12

Table of Resistance Standards 8-13

Chapter 9: D C Ratio 9-1

Non-Ratio Scaling Techniques 9-3

Series-Connected Cells 9-3

Bruce Field's Method 9-4

Standardizing Direct Current 9-4

Quantum Standards Method 9-5

Voltage Ratio 9-5

The Hamon Resistor 9-5

The Kelvin-Varley Divider 9-7

Other Dividers 9-9

Using Direct Voltage Dividers 9-11

Calibrating Direct Voltage Dividers 9-12

Resistance Ratio 9-16

The Potentiometer Method 9-16

Bridge Methods 9-17

Current Methods 9-19


Table of Ratio Standards 9-21

Key References 9-22

Chapter 10: Principles of A C - D C Metrology 10-1

Basic Concepts 10-3

Power Produced by Voltage 10-3

Thermal Converters 10-5

Fluke Solid-State True RMS Sensor 10-6

Single-Element Vacuum Thermocouple

Converters 10-8

Making Transfers 10-9

Determination of Alternating Voltage 10-9

Determination of Alternating Current 10-9

Frequency Effects 10-10

Other AC-DC Devices 10-10

Multijunction Thermocouple

Converters (MJTC) 10-10

Log/Antilog Converters 10-11

Electrostatic and Electrodynamic Instruments . . . . 10-11

Key References 10-11

Chapter 11: Using AC-DC Transfer Standards. . 1 1 - 1

Types of AC-DC Transfer Standards 11-3

Fluke RMS Sensor-Based Standards 11-3

Vacuum Thermocouple-Based Standards 11-4

AC-DC Voltage Transfers 11-5

Plane of Reference 11-6

Frequency Response 11-7

Making the Transfers 11-7

Using the 792A Between Calibration Points 11-8

Preparing to Make Transfers 11-8

Notes on Using a DMM with the 792A 11-10

Using Shunts for AC-DC Current Transfers 11-11

Avoiding Transfer Errors 11-12

4-Terminal Connections 11-12

Connector Considerations 11-12


Distortion and Noise 11-13

Transfer Standard Calibration 11-14

AC-DC Difference 11-14

Range Intercomparison by Half-Scale Bootstrapping 11-14


Chapter 12: Inductance and Capacitance 12-1

Inductance 12-3

SI Definition of Inductance 12-3

Standard of Inductance 12-4

Traceable Standards of Inductance 12-4

Time Constant of Inductance and Resistance

in DC Circuits 12-4

Inductive Reactance in AC Circuits 12-5

Capacitance 12-7

SI Definition of Capacitance 12-7

Realization of the Farad 12-7

Contents

Traceable Standards of Capacitance 12-8

Time Constant of Capacitance and Resistance

in DC Circuits 12-9

Capacitive Reactance in A C Circuits 12-10

Comparing the Currents in Inductors and Capacitors 12-12


Chapter 13: Immittance and A C Ratio 13-1

Impedance, Admittance, and Immittance 13-3

Impedance 13-3

Admittance 13-3

Immittance 13-4

A C Resistance 13-5

Immittance Calibration 13-5

Classical Methods 13-5

Electronic Methods 13-8

A C Ratio 13-10

Impedance Ratio versus Resistance Ratio 13-10

Audio Frequency Dividers 13-12

Resistive Dividers 13-12

Reactive Dividers 13-12

Using Audio Frequency Dividers 13-13

Radio Frequency Ratio 13-15

Connectors and Hook-Up Considerations 13-16


Chapter 14: Time and Frequency 14-1

SI Definition of the Second 14-3

Other Definitions of the Second 14-3

Ephemeris Second 14-3

The Mean Solar Second 14-4

Universal Time 14-4

Coordinating Atomic and Universal Time 14-4

Frequency 14-5

Distribution of Frequency Standards 14-5

Coordination Between Time Scales 14-9

Time Keeping Issues 14-9

Reliability of Atomic Clocks 14-9

Measuring Changes in the Earth's Rotation 14-10


Section Four: Calibrators and Calibration Chapter 15: Multifunction Calibrators 15-1

Stimulus Requirements 15-3

Calibrator Functions 15-3

Calibrator Amplitude Range 15-3

Calibrator Burden and Compliance 15-4

Calibration Protection 15-5

Calibrator Output Noise 15-5

Calibrator Configurations 15-6

Multifunction vs. Single-Function 15-6

Direct vs. Divided Outputs 15-6

Boost Amplifiers 15-6

Calibrator Circuits 15-7

Direct Voltage and Current 15-7

Alternating Voltage and Current 15-8

Resistance 15-9

Wideband 15-10

Calibrator Application Considerations 15-10

Calibrator Environmental Sensitivity 15-10

Calibrator Sources of Uncertainty 15-10

Operating Features 15-13

Manual Operation 15-13

Computer-Controlled Operation 15-13

Calibrator Internal Diagnostics 15-14

Calibrator Procedure Storage 15-14

MFC Calibration 15-14

Calibrator Classes of Uncertainty 15-14

Calibrator Verification 15-14

Calibrator Adjustment 15-14

Comparison of Designs 15-15

DC Voltage 15-15

A C Voltage 15-17


Chapter 16: Artifact Calibration 16-1

Artifact Calibration Development 16-3

Artifact Calibration Process 16-3

The Adjustment Process 16-4

Examples of Artifact-Calibrated

Multifunction Calibrators 16-4

5440A 16-4

5700A 16-5

Artifact Calibration Verification 16-7

Traceability of Artifact Calibration 16-7

Design of the MFC 16-8

The Results of Artifact Calibration 16-8

Data Collection 16-8

Periodic Audits 16-8

Calibration Interval and Performance Prediction 16-9

Comparison of Artifact and Traditional Methods . . . 16-10


Chapter 17: Digital Multimeter Calibration 17-1

Types of DMMs 17-3

Laboratory DMMs 17-3

Bench/Systems DMMs 17-3

Handheld DMMs 17-4

Anatomy of a DMM 17-4

Functional Sections of a DMM 17-4

Analog-to-Digital Converter (ADC) 17-4

Signal Conditioning Circuits 17-6

Alternating Voltage Converters (AVCs) 17-6

Resistance Converters 17-9

Current Converters 17-10

General Calibration Requirements 17-10

Theory of Calibration Adjustment 17-10

Internal References 17-11

A D C Adjustment Considerations 17-12

Integrating ADC 17-12

R 2 A D C 17-12

DC Voltage Range Calibration 17-13

AC-DC Converter Calibration 17-13

Resistance Converter Calibration 17-14

Current Converters Calibration 17-15

Other DMM Calibrations 17-15

Simplified DMM Calibrations 17-15

Closed-Case Calibration 17-15

Closed-Loop Calibration 17-16

Artifact Calibration 17-16

Laboratory DMM Calibration 17-17


Chapter 18: Oscilloscope Calibration 18-1

Types of Oscilloscopes 18-3

Analog Oscilloscopes 18-3

The Basic Analog Oscilloscope 18-4

Digital Storage Oscilloscopes 18-6

Math Operations 18-6

Data Handling 18-6

Combination Oscilloscopes 18-7

Oscilloscope Calibration 18-7

Important Consideration 18-7

Vertical Channels 18-7

Time Base 18-8

DSO Timing 18-8

Performing the Calibration 18-8

Analog Scope Calibration 18-8

DSO Oscilloscope Calibration 18-10

Calibration Equipment Considerations 18-10

Automated Oscilloscope Calibration Systems 18-11

Conclusions 18-11


Chapter 19: Automated Calibration 19-1

The Calibration Process 19-3

Setup Activities 19-4

Day-to-Day Operations 19-4

Adjustments in Workload 19-4

Core Activities for Automation 19-5

Recall 19-5

Calibration 19-5

Documentation 19-5

Benefits of Automation 19-5

Computers and Software 19-6

Operator-Prompted Calibration 19-7

Computer-Aided Calibration 19-7

Closed-Loop Calibration 19-7

Calibration Software Requirements 19-8

Automation and Company Quality 19-11


Section Five: Statistics Chapter 20: Introduction to Metrology Statistics 20-1

Populations of Data 20-3

Distributions 20-3

Distributions vs. TURs 20-4

Normal Distribution 20-5

Mean or Average 20-5

Variance 20-5

Sample Variance 20-6

Standard Deviation 20-6

Sample Standard Deviation 20-6

Uncertainty 20-6

Confidence Level 20-6

Confidence Interval 20-6

Student's t 20-6

Distributions versus Test Uncertainty

Ratios (TURs) 20-7

Computing TURs 20-7

Ideal versus Real World Test Results 20-7

1:1 TURs 20-8

Improving Performance with Statistics 20-9

Discussion 20-9

Contents


Chapter 21 : Statistical Tools for Metrology 21-1

When to Use Statistics 21-3

Statistical Techniques in Metrology 21-4

Estimation 21-4

Prediction Models 21-4

Risk Assessment 21-4

Statistical Process Control 21-4

Histogram Analysis 21-4

Statistical Tests 21-5

Linear Regression (Curve Fitting) 21-8

Classical versus Non-Classical Statistics 21-11

Testing for White Noise 21-11


Chapter 2 2 : Uncertainty Statements 22-1

Documenting Uncertainties 22-3

Definitions 22-3

Error 22-3

Uncertainty 22-3

Confidence Interval 22-3

Confidence Level 22-3

Specified Uncertainty 22-4

Methods of Combining Uncertainties 22-4

Simple Measurements 22-4

Using an Instrument to Better Than Specification. . . . 22-5

Transferring from a Standard 22-5

Characterizing an Instrument 22-7

Indirect Measurements 22-8

Scaling a Standard Value 22-8

Testing Linearity 22-8

Generating a Known Voltage Using Two Standards 22-9

Generating a Precise Voltage with Three Standards 22-10

Chapter 2 3 : Statistical Process Control 23-1

Guidelines for Metrology SPC 23-3

Controlling Measurement Uncertainties 23-3

Types of Control Charts 23-4

Out-of-Control Indicators 23-4

Calculating and Working with Drift 23-5

SPC Applications 23-6

Attributes versus Variables Charts 23-6

Where to Start 23-7

Applying SPC at Fluke 23-7

Applications of Attributes Charts 23-7

Applications of Variables Charts 23-10

Costs and Benefits 23-14


Section Six: Laboratory Management Chapter 24: Service and Maintenance Policy . . . . 24-1

The Laboratory Mission 24-3

Calibration Intervals and Adjustment Policy 24-3

Calibration Intervals 24-3

Adjustment Policy 24-4

Pros and Cons of the Adjustment Policy 24-4

Routine Maintenance 24-5

Mechanical Connections 24-6

Instrument Cleanliness 24-6

Keeping the Customer Informed 24-7

Chapter 25 : The Laboratory Environment 25-1

The Need for Environmental Control 25-3

Site Location 25-4

Laboratory Floor Plan 25-4

Construction 25-4

Electrical Power Requirements 25-5

Line Regulation 25-5

Grounding 25-5

Measuring Ground Resistance 25-6

Ventilation 25-6

Lighting 25-6

Temperature Control 25-6

Monitoring Temperature 25-8

Humidity 25-8

Shielding and Filtering RFI 25-8

Industry Guidelines 25-10

ISARP52.1 25-10

NCSLRP-7 25-10

Chapter 26: Workload Management 26-1

Getting Down to Basics 26-3

Analyzing the Workload and Laboratory Capacity. . . . 26-3

Workload, Capacity, and Turnaround Time 26-4

Realistic Assessment of Basic Capacity and

Cost Factors 26-5

Work Time per Employee 26-5

Labor Rates and Payroll Expense 26-5

Laboratory Overhead 26-5

Contents

Equipment, Facilities, and Procedures 26-6 Start-up vs. Ongoing Operation 26-6 Personnel and Staffing Level 26-6

Information Systems 26-7 Test Equipment Management System 26-7

Chapter 27: Selecting New Test Equipment 27-1 Buying Considerations 27-3

Capabilities 27-3

Reliability 27-4 Ownership Costs 27-5 Life-Cycle Costs 27-5

Acquisition Cost (ACQ) 27-6 Training Cost (TRN) 27-6 Operation Cost (OPR) 27-7

Calibration Cost (CAL) 27-8 Maintenance Cost (MAINT) 27-8 Leverage of Components 27-9

Chapter 28: Laboratory Quality and ISO 9000. . . 28-1 ISO 9000 28-3

ISO 9000 Defined 28-3 ISO 9000 and the Company 28-3 ISO 9000 and the Metrology Laboratory 28-3 How Software Tools Can Help 28-5

ISO 9000 Registration and Quality 28-6 The Quality System 28-6

Focus on Customer Satisfaction 28-7 Organization and Structure 28-8

Preparing for an ISO Audit 28-9 Support from Top Management 28-10 Quality System and ISO 9000 28-11 Typical Scope of Activities 28-11

Expected Results 28-12 Key References 28-12

Chapter 29: Laboratory Accreditation 29-1 Benefits of Accreditation 29-3

Accreditation Process 29-4 Accreditation Bodies 29-4 Accreditation Systems Around the World 29-5 Accreditation Standards 29-5 Relationship Between Accreditation and ISO 9000. . . 29-5 How Accreditation Fits Into Global Measurements. . . 29-6 Key References 29-6

Chapter 30: Laboratory Audits 30-1

Who Requires Audits? 30-3 Who Performs Audits? 30-3

Audit Standards 30-3 Resolving Interpretation Questions 30-4 Preparing For an Audit 30-4

First Impressions Count 30-4 Preparation Identifies Problems 30-4 Self-Audits 30-5

How Important Are Audits? 30-5 Discussion of a Sample Standard 30-5

Organization and Management 30-6 Quality System, Audit and Review 30-6

Personnel 30-7 Facilities and Environment 30-7 Equipment and Reference Materials 30-7

Measurement Traceability and Calibration 30-8 Calibration Methods 30-9 Handling of Calibration Items 30-11

Calibration Records 30-11 Certificates and Reports 30-11 Subcontracting of Calibration 30-13 Complaints 30-14


Chapter 31: Instrument Specifications 31-1 Analyzing Specifications 31-3

Interpreting Specifications 31-4 Confidence 31-4 Beware of the Word "Accuracy" 31-5

Components of a Specification 31-5 Baseline Specifications 31-6

Modifier Specifications 31-7 Qualifier Specifications 31-10

Comparing Specifications: A Detailed Example 31-10

Identifying the Items to be Converted 31-11 Converting the Specifications 31-12 Applying the Confidence Interval 31-12

Other Considerations 31-12 The Workload 31-12 Support Standards 31-13 Manufacturer Support 31-13 Reliability 31-13

Service Philosophy 31-13 Reputation 31-13


IX

Contents

Section Seven: Practical Considerations for Metrology Chapter 3 2 : Grounding, Shielding and Guarding. . 32-1

Grounding 32-3

Ideal vs. Real Ground 32-3

Power Line Ground Systems 32-4

Safety-Ground Ground Loop Errors 32-4

Shielding 32-6

Electromagnetic Radiation 32-7

Shielding from Electric Fields 32-7

Magnetic Field Coupling 32-8

Minimizing Magnetic Pickup 32-9

Magnetic Shielding 32-9

Guarding 32-10

Instrument Guard 32-10

High-Impedance Measurements 32-11

Guarding Current Sources 32-12

Interconnecting Guarded Instruments 32-14

Frequency Limitations 32-15


Chapter 3 3 : A Rogues' Gallery of Parasitics 33-1

Thermal EMFs 33-3

Contact Resistance 33-4

Insulation Resistance 33-5

Surface Leakage 33-7

Dielectric Absorption 33-7

Noise and A C to DC Converters 33-8

Parasitic Capacitance 33-8

Noise from an External Source 33-9

Noise from Transformer Windings 33-9

Noise from a Change in DCV 33-10

Parasitic Inductance 33-10

Bias Current 33-12

Pumpout Current 33-13

Other Rogues 33-14

Chapter 34 : A C Lore 34-1

Classical AC-DC Metrology 34-3

Thomson and Peltier Heating 34-3

Low-Level Voltage Transfers 34-4

Other A C Standards 34-5

True RMS-Responding Thermopile 34-5

Sampling Voltmeter 34-5

Synthesized Voltage Standard 34-5

A C Standard Cell 34-6

Composite Voltages 34-6

Notation for Composite Voltages 34-6

Composite Sinusoidal Voltage Waveforms 34-6

Fourier Series of Non-Sinusoidal

Voltage Waveforms 34-7

Square Waves 34-7

Sine Wave for Comparison 34-8

Sawtooth and Triangular Waves 34-8

Comparing Composite Voltages 34-8

Analyzing Voltage Waveforms 34-9

Graphs of Waves 34-9

Average Voltage 34-10

RMS Voltage 34-10

RSS Voltage 34-10

Sine Wave Parameters 34-10

Composite RSS Voltages 34-12

Measuring Composite A C Voltages 34-12

DC Response 34-13

Harmonic Response 34-13

Internal Phase Shift 34-13

Bandwidth 34-13

Dynamic Amplitude Range 34-14

Appendices Resources R-l

The Metrologist's Bookshelf R-3

National Institute of Standards and Technology (NIST) Information R-3

Calibration and Related Measurement Services (e.g., Electrical Calibration) R-3

Boulder Services (e.g., Time and Frequency

Services) R-3

Other Services R-4

U.S. Naval Observatory (USNO) Information R-4

General Information (Recorded Menu) R-4

Publications and Products List R-4

Local Services R-4

Your National Laboratory R-4

Your Calibration Services Laboratory R-4

Professional Organizations R-4

Professional Conferences R-5

Periodicals R-5

Additional Chapter References R-5

Chapter 4: International Metrology R-5

Chapter 7: Direct Voltage and Current R-6

Chapter 8: DC Resistance R-6

Chapter 9: DC Ratio R-6 Chapter 10: Principles of AC-DC Metrology R-7

Chapter 11: Using AC-DC Transfer Standards R-7 Chapter 12: Inductance and Capacitance R-8 Chapter 13: Immittance and AC Ratio R-8

Chapter 14: Time and Frequency R-8 Chapter 15: Multifunction Calibrators R-9 Chapter 16: Artifact Calibration R-9

Chapter 17: Digital Multimeter Calibration R-10 Chapter 19: Automated Calibration R-10 Chapter 20: Introduction to Metrology Statistics. . . R-10 Chapter 21: Statistical Tools for Metrology R-ll

Chapter 23: Statistical Process Control R-ll Chapter 28: Laboratory Quality and ISO 9000 . . . . R-ll

Chapter 30: Laboratory Audits R-12 Chapter 31: Instrument Specifications R-12 Chapter 32: Grounding, Shielding and Guarding . . R-12 Chapter 33: A Rogues' Gallery of Parasitics R-12 Chapter 34: AC Lore R-12

Contributors C-l

Glossary G-l

Index 1-1

Calibration: Philosophy in Practice

Documents

Transcript of Calibration: Philosophy in Practice