In this second edition of his book Introduction to Electrical Instrumentation, the author has considerably reorganised and extended his coverage to take account of the developments in integrated circuits, particularly the microprocessor, which have made possible the incorporation of programmable and calculating facilities within instruments.
As in the first edition, the aim is to assist the student of electrical or electronic engineering to adopt a systematic and practical approach to his measurement problems. It will also be of value to the engineer or technician who needs to select the right type of instrument for a particular application from among the ranges now offered by many manufacturers.
Some of the important changes in the new edition are: additional material on accuracy and methods of display; the inclusion of intelligent instruments and hybrids in the chapter on digital instruments; increased coverage of interference and screening. In addition, in response to requests from users of the first edition the author has provided a final chapter consisting of problems and exercises (with answers), which will be of great value where the book is used as a course textbook.
Before becoming a lecturer, B.A. Gregory spent more than thirteen years in industry working in the field of instrumentation and measurement. For a number of years he has been a Senior Lecturer, specialising in electrical instrumentation, in the Department of Electrical and Electronic Engineering at Brighton Polytechnic.
Author(s): B.A. Gregory
Edition: 2
Publisher: Halsted Press; John Wiley & Sons
Year: 1981
Language: English
Commentary: Ex libris Noitaenola.
Pages: 446
1. Introduction
1.1 Methods of Measurement
1.1.1 Analogue techniques
1.1.2 Comparison Techniques
Substitution Methods
Null Methods
The potentiometer
Bridges
1.1.3 Digital Techniques
Sampling of data
Transmission of data
Codes
Memories
Controllers
Hardware
Software
Firmware
Programming
System operation
1.2 Display Methods
1.2.1 Analogue Displays
Pointer Instruments
Reading interpretation
Scales
Graphical Instruments
Axes
Permanency of Display
1.2.2 Digital
Light emitting diodes
Liquid-crystal displays
Gas-discharge display devices
Cathode ray tube
Other displays
Choice of display
1.3 Accuracy
1.3.1 Values and Uncertainty
True value
Nominal value
Measured value
Tolerance and uncertainty
Example
1.3.2 Errors
Error of measurement
Example
Sources of error
Summation of Errors
Random Errors
1.3.3 Specifications
Pointer instruments
Digital instruments
Example
1.3.4 Standards
1.3.5 Calibration Procedures
1.4 Input Characteristics
1.4.1 Sensitivity
1.4.2 Scaling
Current division
Voltage division
1.4.3 Matching
1.5 Waveform
1.5.1 Definitions
Sinewave
Mean value
R.M.S. values
Form factor and crest factor
Phase relationships
Power
Bias
1.5.2 Harmonics
1.5.3 Frequency Effects
Bandwidth
Rise time
1.6 Interference
1.6.1 Environmental Interference
1.6.2 Coupled Interference
Electrostatic coupling
Electromagnetic coupling
1.7 Selection
References
2. Analogue Instruments
2.1 Moving Coil Instruments
2.1.1 Null Detectors
Direct Acting Galvanometers
Vibration Galvanometer
Electronic Galvanometer
Sample Specification
Tuned A.C. Detectors
Phase-sensitive Rectifiers (Detectors)
2.1.2 Multimeters
Direct Acting Instruments
Direct current ranges
Example
Direct voltage ranges
Resistance ranges
Example
Alternating current ranges
Alternating voltage ranges
Sample Specification
Electronic Instruments
Direct current ranges
Direct voltage ranges
Resistance ranges
Alternating voltage ranges
Sample Specification
2.1.3 Pen Recorders
Direct Acting Instruments
Electronic Pen Recorders
Writing Systems
Pen
Fibre pen
Pressure stylus
Heated stylus
Electrical stylus
Rectilinear Chart Systems
Sample Specification
2.1.4 Light Spot Recorders
Principle of Operation
Recorder galvanometers
Damping
Transient response
Fluid damped galvanometers
Electromagnetically damped galvanometer
Galvanometer Scaling Circuits
A source of large amplitude
A source requiring a matched load
Electronic signal conditioning circuits
Sample Specification
Operation
Galvanometer Selection Factors
Calibration
Applications
2.2 The Electrodynamic Instrument
2.2.1 Principle
2.2.2 Application
Ammeter and Voltmeter
Wattmeter
2.3 Other Pointer Instruments
2.3.1 Moving Iron Instrument
Properties
2.3.2 Thermocouple Instruments
Properties
Applications
2.3.3 Electrostatic Instruments
Properties
2.3.4 The Q Meter
Applications
Determination of inductor properties
Determination of capacitor properties
2.4 Energy Meters
2.5 Solid State Indicators
2.6 The Cathode Ray Oscilloscope
2.6.1 Conventional Oscilloscope
Principle of Operation
Timebase
Vertical amplifiers
X-Y display
‘Z’ modulator
Sampling oscilloscopes
Screen phosphors
Multiple trace displays
Oscilloscope Accessories
Calibrators
Probes
Cameras
Applications
Voltage measurement
Current measurement
Phase angle measurements
Frequency measurements
Rise time measurements
Sample Specification
2.6.2 Storage Oscilloscopes
Phosphor storage
Mesh storage
2.6.3 Recording Oscilloscopes
2.7 Instrumentation Tape Recorders
2.7.1 Direct Recording
2.7.2 Frequency Modulated Recording
2.7.3 Pulse Duration Modulation Recording
2.7.4 Magnetic Recording Heads
2.7.5 Tape Transport
2.7.6 Tape Motion Irregularities
Properties
References
3. Comparison Methods
3.1 D.C. Potentiometer
3.1.1 Commercial Arrangements
Properties
Applications
3.1.2 Pen Recorders
Process recorders
Flat bed recorders
Sample Specification
X-Y Plotters
3.1.3 Linear Indicators
3.2 A.C. Potentiometer
Example
3.3 D.C. Bridges
3.3.1 Wheatstone Bridge
3.3.2 Low Resistance
3.3.3 High Resistance
3.3.4 Unbalanced Bridge
Principle of operation
Output characteristics
3.4 A.C. Bridges
3.4.1 Classical Bridge
Detectors
3.4.2 Single-ratio Transformer Bridges
Resistance measurement
Capacitance measurement
Other uses
3.4.3 Transformer Double-ratio Bridges
Applications
Capacitance measurement
Measurement of inductance
Measurement of low impedance
Measurements of components ‘in situ’
Network characteristics
Sample Specification
3.4.4 Twin ‘T’ Networks
Principle of operation
3.5 Self-balancing Bridges
Principle of operation
References
4. Digital Instruments
4.1 Counters
4.1.1 Principle of Operation
Asynchronous counters
Synchronous counters
BCD to decimal converters
Operational Modules
Count and display
Internal oscillator
Decade dividers
Main gate
Input circuitry
Selector switches and control logic
4.1.2 Totalise or Count
4.1.3 Frequency Measurement
4.1.4 Period and Multiple-period Measurement
Sample Specification
4.1.5 Frequency Ratio Measurements
Sample Specification
4.1.6 Time Interval Measurements
4.2 Multi-function Digital Voltmeters
4.2.1 Analogue to Digital Conversion
Successive approximation method
Ramp method
Voltage to frequency method
Dual slope technique
4.2.2 Voltage Measurement
Direct Voltage
Sample Specification
Alternating Voltage
Sample Specification
4.2.3 Current Measurement
Sample Specification
4.2.4 Resistance Ranges
Sample Specification
4.3 ‘Intelligent’ Instruments
4.3.1 Concepts
4.3.2 Voltage Facilities
Automatic Calibration
Functional Programs
Uncertainty read out
Percentage deviation
Multiplication
Offset
Ratios
Maximum and minimum
Limits
Statistics
Linearisation
Time
Combination of programmes
4.3.3 Resistance Measurement
4.4 Hybrid Instruments
4.4.1 Component Measurements
Sample Specification
4.4.2 Power Measurement
4.4.3 Recorders
Programmable recorders
4.4.4 Spectrum Analysers
4.4.5 Logic Analysers
Timing Analysers
State Analysers
4.4.6 Data Analysers
Pulse Height Analysers
Correlator
Autocorrelation function
Cross-correlation function
References
5. Transducers
Definitions
Transducers
Fixed reference devices
Mass-spring or seismic device
Transducer classification
5.1 Resistance Change Transducers
5.1.1 Potentiometric Transducers
Example
5.1.2 Resistance Strain Gauges
Gauge factor
Vibratory movement
Temperature effects
5.1.3 Measuring Circuits
Example
Bridge Balancing
Lead resistance
Strain Gauge Attachment
Applications
5.1.4 Resistance Strain Gauge Transducers
5.1.5 Other Resistance Change Transducers
Resistance Thermometer
Hot Wire Anemometers
Humidity Gauges
5.2 Reactance Change Transducers
5.2.1 Capacitance Variation
Variable dielectric
Variable plate area
Variable plate separation
Measuring techniques
5.2.2 Inductance Variation
5.2.3 Linear Variable Differential Transformer (L.V.D.T.)
‘Synchro’
5.3 Semiconductor Devices
5.3.1 Thermistors
5.3.2 Semiconductor Strain Gauges
5.3.3 Photodiodes and Phototransistors
5.4 Self-generating Transducers
5.4.1 Electromagnetic Transducers
Linear velocity transducer
Angular devices
Toothed rotor tachometer
5.4.2 Piezoelectric Transducers
5.4.3 Thermoelectric Transducers
Thermocouple
Output measurement
Thermocouple materials
5.5 Ultrasonic Transducers
5.6 Digital Transducers
Digital encoder
References
6. Signal Conditioning
6.1 Voltage Scaling
6.1.1 Resistance Divider
Resistance chain
Kelvin-Varley divider
6.1.2 Capacitive Divider
6.1.3 Resistance-Capacitance Divider
6.1.4 Inductive Divider
Principle of operation
6.1.5 Voltage Transformer
Example
6.2 Current Scaling
6.2.1 Current Shunts
Four-terminal Shunts
Universal Shunt
Example
6.2.2 Current Transformers
Alternating Current Transformers
Direct Current Transformers
6.3 Attenuators
6.3.1 Resistance Attenuators
Basic Attenuator Pad
Symmetrical T Attenuators
π Attenuators
Balanced Attenuators
6.3.2 Instrument ‘Input Attenuators’
6.4 Filters
Categories
6.4.1 Passive Filters
High Pass Filters
Low Pass Filters
Band Pass Filters
6.4.2 Active Filters
Band Pass Filter
6.4.3 Digital Filters
6.5 Probes
6.5.1 Passive Probes
Input Impedance Effects
Signal Response
Response to step function
Response to sinewave
6.5.2 Active Voltage Probes
6.5.3 Current Probes
6.6 Modulation and Sampling
Modulators
Sampling
6.7 Analogue Processing
6.7.1 Amplification
Attenuated feedback
Charge amplifier
Differential amplifier
6.7.2 Mathematical Functions
Using Operational Amplifiers
Summing amplifier
Computing amplifier
Logarithmic converter
Mean or average values
Using Multipliers
Multiplication
Division
R.M.S. values
6.7.3 Dependent Functions
Voltage to frequency converter
Linearisers
Voltage to current amplifier
6.8 Digital-Analogue Conversion
References
7. Interference and Screening
7.1 Environmental Effects
7.1.1 Thermal Effects
Expansion coefficient
Resistance coefficient
Thermoelectric generation
7.1.2 Humidity Effects
Leakage resistance
Galvanic voltages
7.1.3 Pressure
7.1.4 Multiple Earths and Earth Loops
7.1.5 Inherent Noise
7.2 Component Impurities
7.2.1 Frequency Effects
7.2.2 Resistor Impurities
7.2.3 Inductor Properties
7.2.4 Capacitor Properties
7.2.5 Component Impurity Effects on Signals
7.3 Coupled Interference
7.3.1 Electrostatic Interference
Instrument screen connections
Transformer screening
Amplifier screening
Faraday cage
Guard rings
7.3.2 Electromagnetic Interference
7.3.3 Cross Talk
7.4 Noise Rejection Specifications
7.4.1 Normal Mode Noise
7.4.2 Common Mode Noise
Floating instruments
Example
Example
Guarded voltmeter
7.4.3 Signal-to-noise Ratio
References
8. Instrument Selection and Specification Analysis
8.1 Instrument Selection
Ranges
Accuracy
Response Characteristics
Input Characteristics
Output Characteristics
Stability
Environment
Isolation and Screening
Operation
Reliability
8.2 Specification Analysis
Example
General data
Direct voltage measurement
Resistance measurement
Current measurement
Alternating voltage measurement
Best buy decision
References
9. Instrumentation Systems
Definition
9.1 System Design
Type of System
9.2 Analogue Systems
9.2.1 Open Loop Systems
Problem 1
An outline solution
Problem 2
An outline solution
9.2.2 Closed Loop Systems
9.3 Digital Systems
9.3.1 Data Loggers
9.3.2 Bus-connected Systems
System structure or architecture
The IEC Bus
The data bus
The ‘handshake’ function
General interface management
Addressing an instrument
Operating arrangements
Applications
Data logging
Calibration system
References
10. Problems and Exercises
10.1 Principles
10.2 Analogue Instruments
10.3 Null or Comparison Measurements
10.4 Digital Instruments
10.5 Transducers
10.6 Signal Conditioning
10.7 Interference
10.8 Selection
10.9 Systems
10.10 Answers
Appendix I: Units, Symbols and Conversion Factors
Appendix II: Dynamic Behaviour of Moving Coil Systems
a. Equation of motion; damping magnitude
b. Deflection amplitude of vibration galvanometer
c. Amplitude and phase distortion of a u.v. recorder galvanometer
Appendix III: Equations to Determine the components of a Resistive ‘T’ Attenuator Pad
Index
