Page 80 - Mechanical Engineers' Handbook (Volume 2)
P. 80
Mechanical Engineers’ Handbook: Instrumentation, Systems, Controls, and MEMS, Volume 2, Third Edition.
Edited by Myer Kutz
Copyright 2006 by John Wiley & Sons, Inc.
CHAPTER 3
BRIDGE TRANSDUCERS
Patrick L. Walter
Department of Engineering
Texas Christian University
Fort Worth, Texas
1 TERMINOLOGY 69 5 RESISTANCE BRIDGE BALANCE
METHODS 91
2 FLEXURAL DEVICES IN
MEASUREMENT SYSTEMS 70 6 RESISTANCE BRIDGE
2.1 Cantilever Beams 70 TRANSDUCER MEASUREMENT
2.2 Bourdon Tubes 70 SYSTEM CALIBRATION 93
2.3 Clamped Diaphragms 71 6.1 Static Calibration 93
2.4 Error Contributions from the 6.2 Dynamic Calibration 95
Flexure Properties 72 6.3 Electrical Substitution
Techniques 96
3 THE RESISTANCE STRAIN
GAGE 73 7 RESISTANCE BRIDGE
3.1 Strain Gage Types and TRANSDUCER MEASUREMENT
Fabrication 73 SYSTEM CONSIDERATIONS 102
3.2 Gage Factor 75 7.1 Bridge Excitation 102
3.3 Mechanical Aspects of Gage 7.2 Signal Amplification 103
Operation 75 7.3 Slip Rings 104
3.4 Electrical Aspects of Gage 7.4 Noise Considerations 105
Operation 77
3.5 Technical Societies and Strain 8 AC IMPEDANCE BRIDGE
Gage Manufacturers 80 TRANSDUCERS 111
8.1 Inductive Bridges 112
4 THE WHEATSTONE BRIDGE 81 8.2 Capacitive Bridges 114
4.1 Bridge Equations 82
4.2 Lead Wire Effects 85 REFERENCES 115
4.3 Temperature Compensation 87
BIBLIOGRAPHY 115
1 TERMINOLOGY
A telemetry system responding to a measurand consists of four basic parts—the transducer,
the transmitting system, the receiving system, and the data output or display system:
Telemetry. The transmission of information about a measurand.
Measurand. The object of a measurement. The process to be defined.
Transducer. A component in the telemetry system which provides information about a
process and, as a by-product, transfers energy from the process. Typical bridge trans-
ducers convert physical quantities such as force, pressure, displacement, velocity,
acceleration, temperature, and humidity into electrical quantities for input to the trans-
mitting system.
Reprinted from Instrumentation and Control, Wiley, New York, 1990, by permission of the publisher.
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