Instrumentation for Test & Measurement Professional Development Technical Training Short Course...
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Instrumentation for Test & Measurement
Based onthe
Sensor Technology Handbook
•A sample of the 572 slides
in the course
The Course• Based on the “Sensor Technology Handbook”
edited by Jon Wilson, published by Newnes/Elsevier, copyright 2005, 691 pages plus CD.
• Some slides contain figure numbers. They refer to the book figures.
• This course covers only the highlights of the book.
• For discount order form, contact instructor.
Performance Characteristics
• Transfer Function– Curve of Output/Input
• Sensitivity– Slope of Transfer Function
• Span or Dynamic Range– Usable Range of Inputs
• Accuracy or Uncertainty– Largest Expected Error
• Hysteresis– Output Difference, Increasing & Decreasing
Performance Characteristics (2)
• Nonlinearity (Linearity)– Deviation of Transfer Function From Straight Line
• Noise– Extraneous Output Added to Signal
• Resolution– Minimum Detectable Signal Fluctuation
• Related to Noise Spectrum
• Bandwidth & Frequency Response– Usable Frequency Range & Variation of Sensitivity
Some Sensor Characteristics
Smart Sensors
The Measurement
• Expected Amplitude Range
• Expected Frequency Range
• Expected Environment
• Economic Constraints
• Installation Constraints
• Available Instrumentation
The Data Sheet
• Filtering the Data Sheet
• What is Pertinent?
• Interpreting the Data Sheet
• Getting Clarification– Literature
– Experts & Consultants
– Manufacturers
System Considerations
• Sensor Characteristics
• Interconnections
• Signal Conditioner Characteristics
• Data Acquisition Characteristics
• Readout Characteristics
• Data Validation
• Analysis and Interpretation
Instrument Selection
• Sensor Environment• Sensor Performance Characteristics• Sensor Electrical Characteristics• Sensor Size and Weight• Sensor Mounting• Cable Environment• Cable Performance Characteristics• Cable Mechanical Characteristics
Instrument Selection (2)
• Power Supply Environment
• Power Supply Performance
• Power Supply Size and Weight
• Amplifier Environment
• Amplifier Performance
• Amplifier Size and Weight
Quantifiable Measurements
• REQUIRE:
• What is the Measurand?
• What is the Environment?
• What Uncertainty (Accuracy) is Required?
• Whole System Calibrated & Traceable?
• Appropriate Sensor is Necessary, But Not Sufficient.
Sensor Resistances
Bridge Configurations
Minimizing Offset Errors
Noise Sources
DC Errors
ADC TypesADC’S FOR SIGNAL CONDITIONING
Successive Approximation• Resolutions to 16-bits• Minimal Throughput Delay Time• Used in Multiplexed Data Acquisition SystemsSigma-Delta• Resolutions to 24-bits• Excellent Differential Linearity• Internal Digital Filter, Excellent AC Line Rejection• Long Throughput Delay Time• Difficult to Multiplex Inputs Due to Digital Filter Settling TimeHigh Speed Architectures:• Flash Converter• Subranging or Pipelined
PE Amplifier Circuit
CCD Arrays
Technology Fundamentals
• Piezoelectric
• “Crystal” type
• Self-generating
• Piezoelectric materials– Natural (monocrystalline)
– Piezoceramic (polycrystalline)
IEPE Sensor System
MEMS PR Construction
MEMS VC Accelerometer
Selection Process
• Frequency range?
• Sensitivity or amplitude range?
• Environment, especially temperature?
• Size and mass restraints?
• Mounting configuration?
• Consult manufacturer’s application engineers?
Interfacing and Designs
Overview
Biosensor characteristics
• Sensitivity• Selectivity• Range• Response time• Reproducibility• Detection limit• Life time• Stability
Transduction Mechanisms
• Amperometry• Potentiometry• Photometry• PE materials• Conductimetric• Thermometric• Enzyme thermistor• FET transducer
Biosensor configurations
Mass Spectrometer Schematic
Mass Spectrometer
Inductive Sensors
• “Eddy current sensors”
• Require conductive targets
• Not affected by gap material
• Sensitive to target material
• Nanometer resolutions
• > 80 kHz
• Minimum target thickness requirement
Selecting and Specifying
• Physical configuration
• Output, Range
• Offset, Standoff
• Sensitivity, Linearity, Resolution
• Bandwidth
• Thermal errors
• Accuracy
Comparing Capacitive and Inductive Sensors
Latest Developments
• Little change in sensors
• Advances in electronics
• Miniaturization
• Embedded electronics
• Digital interface
Inductive Sensor (LVDT)
Hall Effect Sensor
10. Flow and Level Sensors
Mass, volume, laminar, turbulent flow. Hydrostatic, ultrasonic, RF capacitance,
magnetostrictive, microwave level.
Methods for Measuring Flow
• Thermal anemometers• Differential pressure• Vortex shedding• Positive displacement• Turbine-based• Mass (Coriolis)• Electromagnetic• Ultrasonic• Laser
11. Force, Load & Weight Sensors
Piezoelectric & Strain Gage
Load Cell
12. Humidity Sensors
Capacitive, resistive & thermal conductivity
Selecting and Specifying
• Accuracy, Repeatability, Interchangeability
• Stability, Condensation recovery
• Contamination resistance, Size & packaging
• Cost effectiveness, replacement cost
• Calibration
• Complexity of signal conditioning
Interfacing and Design
• Output affected by temperature & RH
• Temperature compensation required for best accuracy
• Industrial grade sensors incorporate RTD on the ceramic substrate
• RHIC output depends on supply voltage, RH and temperature
Photosensors
• Quantum detectors convert photons to electrons
• Thermal detectors absorb radiant energy and measure temperature change
IR Detector Spectral Responses
16. Pressure Sensors
Gauge
Absolute
Differential
Many technologies
• Silicon strain gages (Piezoresistive)
• Variable reluctance
• Variable capacitance
• Fiber optic
• Piezoelectric
• (Every company that makes any kind of sensor makes pressure sensors)
Types of pressure measurement
• Gauge
• Differential
• Absolute
• Vacuum gauge
• All are actually differential, with different references
Latest & Future
• Miniaturization
• Higher temperatures
• Sensor identification– Smart sensors (IEEE1541)
– SAW tag
• Wireless
20. Temperature Sensors
Basic types
• Contact: the sensor is in contact with the medium or object being measured
• Non-contact: interprets the radiant energy of a heat source in the form of infrared radiation– Useful on non-reflective solids and liquids
– Not useful with gases because of their transparency
21. Nanotechnology-Enabled Sensors
Smaller than small; atomic level
More possibilities
• Increasing integration of materials, devices and systems
• “nanotech takes the complexity out of the system and puts it into the material”
• Single molecule detection
• Nanotech data storage 10^12 bits/sq. in.
• High volume production of tiny, low-power smart sensors
Nano-array of Cantilevers & Electronics
Introduction to Wireless Sensor Networks
• Increase reliability of data gathering
• Reduce deployment costs
• Minimize long term maintenance costs
• Reduce cabling and connector costs
• Ideal system is networked and scalable– Low power, smart, programmable, fast data rate,
reliable, accurate, stable
• Integrated sensor, electronics, communication
Industrial Application