194 Vibration and Shock Test Control Techniques

For Whom Intended  Engineering or technical personnel involved in specifying, tailoring (e.g. MIL-STD-810) and performing state-of-the-art random vibration and shock tests; those who obtain/analyze/review field and laboratory test data; and those who design/certify hardware/structures/instrumentation to meet dynamic environmental requirements. Members of the automotive, aerospace, aircraft, shipboard and weapons technical communities will benefit.

Brief Course Description  (See course outline, below.) The objective of the first portion of the course (also available separately as Course 196, Digital Data Acquisition) is to provide participants with the knowledge required to specify, evaluate and use a wide variety of digital data acquisition systems in laboratory and field applications. Basic principles of sampling and digitizing theory are presented and reinforced with practical examples from everyday testing operations.

Hardware discussions concentrate on performance capabilities and practical problems that arise in laboratory and field applications. Heavy emphasis is placed on new technologies and system concepts that will be available in the near future. The aim is to prepare participants to design and procure state-of-the art systems that will satisfy their technical requirements efficiently and economically.

Literature describing the latest available hardware will be used as examples of good (and bad) practice. Particular emphasis will be placed on critical evaluation of commercially-available hardware and software systems.

The objective of the second part of the course  (also available separately as Course 194-3) is to provide an overview of vibration testing technology with emphasis on the practical everyday problems that are encountered in testing laboratories. Empha­sis is placed on the basic prin­ciples of vibration hardware, control systems, and anal­ysis tech­niques used for random, sine, and shock testing. Capa­bili­ties and limitations of available sys­­tems will be dis­cussed.

This course presents an application-oriented ap­proach to digi­tal computer control of random vibration and shock testing on shakers and analysis of vibration and shock data. Complex mathematical concepts are reduced to graphic form for intuitive understanding. Illustrative exam­ples from the “real world” are used throughout.

The course is presented as a series of highly inter­active lec­ture­/discussion sessions. Problems for indi­vidual and group solution are interspersed through­out the course to act as training aids and to eval­uate class progress. Spe­cial-interest dis­cussions are en­cour­aged outside of the regular course sessions.

Prerequisites  Participants should previously have participated in TTi’s Course 116, Fundamentals of Vibration courses, or in training offered by vibration equipment manufacturers, also TTi course 163, Instrumentation for Test and Measurement, or equivalent training. In addition, it would be helpful if participants have some experience in specifying and/or conducting computer-controlled tests on shakers and some exposure to spectrum analysis.

Diploma Programs  This course is required for TTi's Dynamic Test Specialist (DTS) Diploma Program and may be used to satisfy the course 196 requirement of the Data Acquisition & Analysis Specialist (DAAS) Diploma program. It may be used as an optional course for any other TTi specialist diploma program.

Related Courses  TTi’s open Course 194 (this course) combines the content of Course 194-3 with Course 196, Digital Data Acquisition, which runs concurrently. Course 194-3 is intended for on-site presentations only.

Text  Each student will receive access to the on-line electronic course workbook, including most of the slides used in the course presentation. An initial subscription is included in the price of the course and renewals are available for an additional fee.

Internet Complete Course 194 features over 18 hours of video as well as more in-depth reading material. All chapters of course 194 are also available as OnDemand Internet Short Topics. See the course outline below for details.

Course Hours, Certificate and CEUs  Class hours/days for on-site courses can vary from 14–35 hours over 2–5 days as re­ques­ted by our clients. Upon suc­cessful course completion, each partici­pant re­ceives a certi­ficate of completion and one Con­tinu­ing Edu­ca­tion Unit (CEU) for every ten class hours.

Click for printable (PDF) outlines: Course 194-3 (on-site only)  or Course 194 (full open course).


Course Outline

Chapter 1, Course 196 - Course Overview, Objectives

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  • Objectives
  • Theory
  • Hardware
  • Analysis
  • System Specification and Evaluation

Chapter 2, Course 196 - Role of Data Acquisition

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  • Experiment Mission
  • Measurements/Transducers
  • Specimen-to-Data-Acquisition Connection
  • Data Acquisition
    • Computer Interface
    • “Computer”
    • Data Storage
  • Data Analysis
  • Test/System Type Categorization

Chapter 3, Course 196 - Basic Concepts and Terminology in Data Acquisition

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  • Time History
    • Time-History Properties
    • Spectra
    • Time and Frequency Domain
    • Spectrum Calculation ... Comb Filter Analogy
    • The Spectral View
    • The Fourier Transform .. Properties
    • Time History/Spectra Examples
    • Time History/Spectra Equivalence
  • Transfer Functions
    • Low Pass Filter—Transfer Function Interpretation
  • Decibels

Chapter 4, Course 196 - Accuracy, Precision, Errors and Dynamic Range

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  • Accuracy and Precision—Definition
  • Measurement Model
    • Ideal vs. Perfect
  • The Transfer Function of Signal-Path Components
    • The System Transfer Function
  • Errors
    • Deviations From the Assumed Model—Linearity
    • Linearity Characterization
    • Differential Nonlinearity
  • Accuracy and Dynamic Range
    • Dynamic Range
    • Headroom—Designing for the Unexpected
    • Finding Small Effects in Large Data
    • Accuracy and Dynamic Range—How are they Quantified?
  • Errors… Re: Full Scale or Re:Reading
    • Errors.. Time-Domain Characterization… “DC” Accuracy
  • SpecsManShip...Lying with Statistics
  • A Diversion… What Does RMS Error Mean?
  • Accuracy/Dynamic-Range Characterization
    • Dynamic Range vs. Accuracy
  • Sources of Error
    • Bias and Random Errors
    • Classical Error Analysis
  • AC/DC Coupling
  • “Out-of Band” Energy

Chapter 5, Course 196 - Digitizing Theory

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  • Digitizing Theory—Bits, Bytes, Words
    • Bytes
    • Kilo, Mega, Giga, Terra, Peta…Googol
    • Coding Conventions
  • The Analog-to-Digital Transformation
    • The BiPolar A-to-D...Offset Binary Coding
    • A/D Conversion Characteristics
    • A/D Conversion “Gross Errors”
    • A/D Conversion “Small Errors”
    • A/D Resolution
    • Resolution vs. Number of Bits
  • Full Scale Sine Input Dynamic Range—“Effective Bits Test”
    • Dynamic Range—“Effective Bits Test” Spectral Calculation
    • Real System Dynamic Range Characterization
    • Dynamic Range…Zero-Input Response
    • The Effect of Analysis Bandwidth
    • How Many Bits are Needed?
    • The “Effective Bits” Test
    •  “Effective Bits” Results
    • What’s The Difference?
    • Which Characterization Should be Used?
    • An Alternate Effective Bits Calculation

Chapter 6, Course 196 - Sampling Theory — Aliasing

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  • Sampling Theory—Digitizing “Rules”
    • How Often to Sample?
    • Conventional Wisdom
    • Shannon’s Theorem
  • Digitizing With various numbers of Points/Cycle
  • Aliasing Example
    • Aliasing: Correctly Sampled Set
    • Aliasing: Undersampled Set
    • Aliasing Example .. Comparison of Data Sets
  • The Spectral View
  • Aliasing.. Viewed as Folding
  • The Insidious Part
  • Where Does the Aliased Data Appear?
  • Aliasing Example .. Sine Signal
  • Aliasing/Multiple Folding
    • Another View of Folding (and a Trick!)
    • The Way It has been Done So Far
    • “Undersampling”
  • The Aliasing Diagram
  • Critical Points

Chapter 7, Course 196 - Hardware

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  • System Elements
  • Signal Conditioners
  • Amplifiers
    • Gain
    • Common-Mode Rejection
    • Measurements
    • The Way it is Done
    • The Ideal Differential Amplifier
  • “Normal-Mode” Voltage
  • Common Mode Voltage
    • Common Mode Error
    • Common Mode Rejection Ratio
  • Problem .. Induced Noise
    • Objective .. Reduce the Effects of Induced Noise
    • Noise Rejection .. Differential Input
    • Twisted Pair Conductors
  • Shielding
    • Shield Connection
    • Shield Termination
      • Balanced Input
      • Amplifier Common
      • Full Bridge
      • Single-Arm Bridge
      • Thermocouples
  • The Real Differential Amplifier (and Source)
  • Real Differential Amplifier and Source .. Effect
  • Instrumentation Amplifier .. Implementation
  • Power-Supply Restrictions
  • Problem .. Measure Small Voltage Differences in a High Common-Mode Environment.
  • Isolation Amplifier .. Concept
  • IEPE Transducer Cabling

Chapter 8, Course 196 - Alias Protection

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  • Pyrotechnic Test Data Set Example—Alias-Protection
    • Solution #1: Sample Really Fast
    • Solution #2: Analog Anti-Alias Filters
  • Filters
    • The Basic Low-Pass-Filter Concept
    • Brick-Wall vs. Real Filters
    • How Filters Behave
  • Aliasing Analysis
    • Anti-Alias Filters … Hardware
    • Complex Filter “Construction”
    • Building a Filter
  • Group Delay
  •  “Classical” Filter Types
    • Bessel Filters
    • Butterworth Filters
    • Elliptical Filters
  • Low-Pass Filter Comparison… Spectral Domain
  • Filter Characteristic
  • Filter/Sample-Rate
  • Trade-Offs
  • Aliasing…Revisited
    • Aliasing Analysis—Assumption #1—Physical Considerations
      • Pyrotechnic Test Data Set
    • Assumption #2…Filter Cutoff Frequency
  •  Sampling Ratio Calculation
    • The fR /fCR Ratio
    • Performance of Different Filters
    • Minimum Sampling Ratios for Different Filters
    • The Aliasing Diagram—Filter/Alias Analyzer
    • Anti-Alias Filter Effect (1.61 Points/Cycle)
    • Removing Aliased Data
  • How to Tell Whether a Data Set is Aliased
    • Good and Bad (Ugly)
  • “Digital” Anti-Alias Filters
  • AC/DC Coupling
    • Why do AC Coupling?
    • AC-Coupling to Remove Offset
    • AC-Coupling Methods
    • Capacitive AC Coupling
    • Offset Subtraction … Analog
    • Offset Subtraction … “Digital”
    • Recommendation
    • The Downside of AC-Coupling
    • AC-Coupling Distortion—More Examples

Chapter 9, Course 196 - Multiplexers

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  • Multiplexers—Function
  • Types of Multiplexers
    • Mechanical
    • Solid State
    • Single-Ended/Differential
    • Multi-Tier
  • Solid-State Multiplexers—Switching Time
  • A Problem with Multiplexers—Crosstalk
  • Sample and Hold Amplifiers
    • Function
    • Operation
    • Real S&H Amplifiers

Chapter 10, Course 196 - Analog-to-Digital Converters

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  • Analog-to-Digital Converters—Function
  • Flash/Parallel A/D Converters
  • Successive Approximation A/D Converters
  • Digital-to Analog (D/A) Converter
  • Successive Approximation Converters
    • Operation
    • Changing Signal
    • Near ½ Scale
  • Aliasing Protection
  • Oversampling Converters
    •  Implementation
    • Higher Speed
    • The Solution… A 1-Bit Converter
  • Sigma Delta (High-Ratio) Oversampling—Alias Protection
    • Sigma Delta Modulation
    • Sigma Delta Filter/Decimator
    • Sigma-Delta A/D .. Actual Implementation
    • Sigma-Delta Filter Characteristic
    • Delay Characteristics
    • Interesting Behavior
    • System Applications
    • Lower Sample Rates
    • Sigma-Delta Converters Pro/Con
  • Sampling Ratio Requirements (Revisited)
  • The Alias Test—for Some SD Systems
  • Sigma Delta—Caveat Emptor
  • Averaging or Integrating A/D Converters
    • Averaging A/D ..Principle
    • Integrating Converters—Noise Rejection
  • Dual-Slope A/D Converters

Chapter 11, Course 196 - Real System Configurations

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  • The “Fundamental” Component(s)
  • Minimum, Single-Channel System
  • Single-Channel System with A-A Filter
  • Multi-Channel .. A/D Per Channel
  • Multi-Channel .. Minimum Multiplexed System
  • Multi-Channel ..Differential Multiplexer
  • Amplifier-Per-Channel Multiplexed System
  • Amp/Filter-Per-Channel Multiplexed System
  • Simultaneous Sample-and-Hold System
  • Oversampling/Sigma Delta Converter System
  • Transient Recorders/Digital Oscilloscopes
  • Transient Recorder “Feature” .. Pre-Trigger
  • “Transient Recorder” Extensions

Chapter 12, Course 196 - The Computer and The Data Acquisition System

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  • Interfaces
    • The Computer Interface
    • Serial Interfaces (Classical)
    • Serial Interfaces (Modern)
    • Parallel Interfaces
    • Data Transfer Concepts
  • Data Transfer Mechanisms
    • Programmed I/O
    • DMA I/O
    • Double-Buffering
    • Chaining
    • Getting Data to Storage
    • Interrupts
    • FIFO Memory
  • “Hosts” and “Buses”
    • The Computer
    • Host Options for Data Acquisition
    • PC-Computers .. Hardware.. 2013
    • Getting Data to Disk
      • Disk Fragmentation
      • Disk Arrays
      • RAID Disk Arrays
      • JBOD Disk Array
    • Transfers, Scans, and Buffers
    • PC Systems (“Clones”)
    • PC-Computers .. Software
    • Buses
      • The ISA Bus for Data Acquisition
      • The PCI Bus for Data Acquisition
      • The PCI-Express Bus for Data Acquisition
      • The Compact PCI/PXI Bus
      • The VME Bus
      • The VXI Bus
      • Universal Serial Bus (USB 2.0)
    • Wi-Fi
    • Ethernet (Gigabit)
  • “Architectures”
    • Performance Improvement vs. Time
    • System Conception ... Questions
    • PC System Architectures
    • Peripheral Processors
    • Eavesdropping

Chapter 13, Course 196 - Data Analysis

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  • Counts to Engineering-Unit Conversion
    • Counts-to-Volts Conversion
    • Volts-to-Engineering Units (EU) Conversion
    • Polynomial Approximation
    • Linear Segment Approximation
  • Noise Reduction, Smoothing and Filtering
    • Noise Removal (Filtering)…“Smoothing by N”
    • Noise Removal…Exponential Smoothing
    • Exponential vs “by N” Smoothing…Time Response
    • Exponential vs “by N” Smoothing…Filter Shape
    • Filtering in the Spectral Domain
  • Data Resampling (Interpolation)
    • Time-Domain Interpolation
    • Resampling/Interpolation…Example
    • Pulse Interpolation Example
    • Data Interpolation…When is it Needed?
  • Instrumentation and Filter Distortion Correction
    • DownSampling
    • One Strategy (that Minimizes Sample Rate)
    • Problem …. The System Transfer Function
    • The Effect of Signal-Path Components
    • Making Results Agree/What Does “Normalize” Mean?
    • Defining a “Standard System Transfer Function”
    • System Transfer-Function-Normalization Function
    • Satisfying Standards (SAE)
  • Recommendations
    • Shock (SRS) Testing…
    • Recommendation: Vibration & Acoustic Testing
  • Removal of Aliased Data from Time Histories
    • Time History Analysis-Alias Signal Rejection
    • Sampling Strategy
    • Analog (Anti-Alias Filter 4-Pole Bessel at 8 kHz)
    • Analog Low-Passed—4 Pole Bessel at 8 kHz
    • Acquired Data—20 K S/S
    • Low Pass Filtered (Digital) at 4110 Hz
  • A Better Sampling Strategy

Chapter 14, Course 196 - System Specification and Evaluation

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  • The System-Specifier’s View
  • Specification Topics
    • System Accuracy Specification
    • System Source Options
    • The Vendor’s Job
  • Evaluating Systems…Simple Tests
    • Testing Toolkit
    • Test 1: Shorted-Input Noise…the Simplest Test
    • Test 2: Crosstalk
    • Test 3: Frequency Response…In-Band Behavior
    • Test 4: Frequency Response…Out-Of-Band Behavior
  • Out-of-Band Behavior Analysis
  • What Slew Rate is Required?
  • Input Saturation Behavior
  • Common-Mode Behavior (for Differential Systems)
  • A More Critical Test…Effective Bits
    • Effective Bits…the Basic Idea
    • The Effective Bits Analyzer
    • Analysis Steps
    • Effective Bits---Error Calculations
    • The Spectrum of the Error (Normalized)
    • Some Effective Bits Results
  • System Specs—What Do They Mean??
    • Details on the “Standard” Test
    • What Do Specific Users Care About?

Chapter 15, Course 196 - Data Acquisition Review and Summary

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  • Critical Points
  • Dealing with the Pitfalls—Doing it Right
  • Aliasing Errors
  • Amplifiers and Cabling—Induced-Noise Rejection
  • Anti-Alias Filter Distortion
  • Predictions are Hard, Especially about the Future
  • Test-Organization Philosophy

Chapter 1, Course 194 - Basic Concepts and Terminology in Test Control

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  • The Linearity Assumption
  • A Few Simple Circuits/Responses
  • Vibration Modes
  • Spectral Plot Formats

Chapter 2, Course 194 - Vibration Environment Simulation Hardware

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OnDemand Short Topics$100.00
  • Vibration Exciters
  • Fixtures
  • Command Generation

Chapter 3, Course 194 - Testing Objectives/Philosophy and Simulation Concepts

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  • Environment Assessment
  • Damage Potential
  • Test Specification
  • “MIL-STD” Testing
  • ESS, HASS, HALT

Chapter 4, Course 194 - Measurement Systems

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  • Transducers
  • Signal Conditioning
  • Data Acquisition

Chapter 5, Course 194 - Basic Analysis and Control Tools

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OnDemand Short Topics$150.00
  • Fourier Transforms
  • Power Spectral Density
  • Transfer Functions
  • Linear Systems
  • Forced-response Analysis
  • Control System Concepts

Chapter 6, Course 194 - Transient Testing

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  • Objectives
  • Transient/Shock Excitation
  • Analysis .. Shock Response Spectra
  • Desired Time Histories
  • Special Problems

Chapter 7, Course 194 - Random Testing

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  • Objectives
  • Control
  • Analysis

Chapter 8, Course 194 - Sine Testing

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  • Concepts
  • Analysis
  • Control Strategies

Chapter 9, Course 194 - Multiple-Degree-of-Freedom Systems

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Appendix A - Glossary of Terms

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Appendix B - Buzzwords and Jargon

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Appendix C - Sample Data Acquisition System Specification

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Appendix D - Characterizing Errors and Dynamic Range/SpecsManship...the Fine Art of Lying With Math & Statistics

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OnDemand Short Topics$25.00

Appendix E - Technical Articles and Demonstration Programs

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OnDemand Short Topics$25.00

Final Wrap-up

  • Student Topic/Problem Discussion
  • Final Review
  • Award of Certificate for Successful Completion

Click for printable (PDF) outlines: Course 194-3 (on-site only)  or Course 194 (full open course).

Revised 180906