Mechanical Measurements

Summary

In the field of mechanical measurements, Mechanical Measurements continues to set the standard. With an emphasis on precision and clarity, the authors have consistently crafted a text that has helped thousands of students grasp the fundamentals of the field. Mechanical Measurements gives students a methodical, well thought-out presentation that covers fundamental issues common to all areas of measurement in Part One, followed by individual chapters on applied areas of measurement in Part Two. This modular format fits several different course formats and accommodates a wide variety of skill levels. The separate areas of applied measurements help students see the relevance of mechanical measurement to their own field of interest and offer motivation by addressing real-world measurement problems. The new fifth edition builds on these hallmark features and contains many new topics that reflect changes in the field. A revised chapter on uncertainty analysis reflects the new ASME standards for estimation of uncertainties and provides students with more detailed coverage of the subject. A revised chapter on signal processing gives students more complete coverage of measurement circuit analysis and includes procedures for finding responses of filters and op amps. The increased material on digital measurements provides improved coverage of analog to digital conversion and digital sampling theory, more effectively explaining how computers acquire and store data. The enhanced coverage of electronic instrumentation and electronic sensors helps students better understand this critical area.

Fundamentals of mechanical measurement
The Process of Measurement: An Overview
The significance of mechanical measurement
Fundamental methods of measurement
The generalized measuring system
Types of input quantities
Measurement standards
Calibration
Uncertainty: accuracy of results
Reporting results
Standards and Dimensional Units of Measurement
Establishment of dimensional standards
Historical background of measurement standards in the United States
The SI system
The standard of length
The standard of mass
Time and frequency standards
Temperature standards
Electrical standards
Conversion between systems of units
Significant digits, rounding, and truncation
Assessing and Presenting
Experimental Data.Common types of error
Introduction to uncertainty
Estimation of precision uncertainty
Theory based on the population
Theory based on the sample
Goodness of fit
Statistical analysis by computer
Bias and single-sample uncertainty
Propagation of uncertainty
Examples of uncertainty analysis
Minimizing error in designing experiments
The Chi-Squared (x2) distribution
Graphical presentation of data
Line fitting and the method of least squares
The Analog Measurand: Time-Dependent Characteristics
Simple harmonic relations
Circular and cyclic frequency
Complex relations
Frequency spectrum
Harmonic, or Fourier, Analysis
Amplitudes of waveforms
The Response of Measuring Systems
Amplitude response
Frequency response
Phase response
Predicting performance for complex waveforms
Delay, rise time, and slew rate
Response of experimental system elements
Simplified physical systems
Mechanical elements
An example of a simple mechanical system
The importance of damping
Dynamic characteristics of simplified mechanical systems
Single-degree-of-freedom spring-mass damper systems
The zero-order system
Characteristics of first-order systems
Characteristics of second-order systems
Electrical elements
First-order electrical system
Simple second-order electrical system
Calibration of system response
Sensors.Loading of the signal source
The secondary transducer
Classification of first-stage devices
Variable-resistance transducer elements
Sliding-contact devices
The resistance strain gage
Thermistors
The termocouple
Variable-inductance transducer elements
The differential transformer
Variable-reluctance transducers
Capacitive transducers
Piezoelectric sensors
Semiconductor sensors
Light-detecting transducers
Hall-effect sensors
Some design-related problems
Signal Conditioning
Advantages of electrical signal conditioning
Modulated and unmodulated signals
Input circuitry
The simple current-sensitive circuit
The ballast circuit
Voltage-dividing circuits
Small changes in transducer resistance
Resistance bridges
Reactance or impedance bridges
Resonant circuits
Electronic amplification or gain
Electronic amplifiers
Vacuum-tube amplifiers
Solid-state amplifiers
Integrated circuits
Operational amplifiers
Special amplifier circuits
Shielding and grounding
Filters
Some filter theory
Active filters
Differentiators and integrators
Component coupling methods
Digital Techniques in Mechanical Measurements
Why use digital methods? Digitizing mechanical inputs
Fundamental digital circuit elements
Number systems
Binary codes
Some simple digital circuitry
The digital computer as a measurement system tool
Data processors, computers, microcomputers: the computer hierarchy
The microprocessor
The microcomputer
Analog-to-digital and digital-to-analog conversion
Buses
Getting it all together.9
Readout and Data Processing.The electronic counter
Analog electric meter indicators
Meters with electronic amplification
Digital-readout multimeters
The cathode-ray os
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Excerpts

After more than 30 years, the basic purpose of this book can still be expressed by the following three paragraphs extracted from the Preface of the first edition of Mechanical Measurements, published in 1961. Experimental development has become a very important aspect of mechanical design procedure. In years past the necessity for "ironing out the bugs" was looked upon as an unfortunate turn of events, casting serious doubts on the abilities of a design staff. With the ever-increasing complexity and speed of machinery, a changed design philosophy has been forced on both the engineering profession and industrial management alike. An experimental development period is now looked upon, not as a problem to avoid, but as an integral phase of the whole design procedure. Evidence supporting this contention is provided by the continuing growth of research and development companies, subsidiaries, teams, and armed services R & D programs. At the same time, it should not be construed that the experimental development (design) approach reduces the responsibilities attending the preliminary planning phases of a new device or process. In fact, knowledge gained through experimental programs continually strengthens and supports the theoretical phases of design. Measurement and the correct interpretation thereof are necessary parts of any engineering research and development program. Naturally, the measurements must supply reliable information and their meanings must be correctly comprehended and interpreted. It is the primary purpose of this book to supply a basis for such measurement. With the fifth edition of Mechanical Measurements considerable changes and improvements have occurred. Foremost a new co-author, Dr. John H. Lienhard, has been added. In addition, more than half of the chapters in the book have been substantially revised. Some specific changes are as follows: The uncertainty material in Chapter 3 has been fully revised and follows the ASME standards. New material on discrete sampling and discrete Fourier transforms has been added in Chapter 4 and also in Chapter 8. New material on semiconductor sensors has been added in Chapter 6 and also in Chapter 16. The sections on filters and op-amps in Chapter 7 have been revised and updated. Laser-based velocity and displacement measurement has been introduced in Chapter 15 and also in Chapters 11 and 17. New material on sound intensity and noise measurement has been added in Chapter 18. Recent changes in measurement standards are incorporated in Chapter 2. The remainder of the material has been substantially updated, and approximately 40 percent of the problems have been replaced or revised. The authors do not suggest that the sequence of materials as presented need be strictly adhered to. Wide flexibility of course contents should be possible, with text assignments tailored to fit a variety of basic requirements or intents. For example, the authors have found that, if desired, Chapters 1 and 2 can simply be made a reading assignment. Greater or lesser emphasis may be placed on certain chapters as the instructor wishes. Should a course consist of a lecture/recitation section plus a laboratory, available laboratory equipment may also dictate areas to be emphasized. Quite generally, as a text, the book can easily accommodate a two-semester sequence. Acknowledgments The authors would like to thank Senior Editor Eileen Bernadette Moran, Editorial Assistant Dana Goldberg, and the entire staff at Addison-Wesley for their energetic assistance in assembling the fifth edition. Roy Marangoni would like to express his gratitude to Dr. Joel E. Peterson for the material on digital counters and digital recording, which was adapted from his lecture and laboratory notes at