Doe Fundamentals Handbook Instrumentation And Control Volume 1 of 2
Department of Energy
Fundamentals Handbook INSTRUMENTATION AND CONTROL
Module 1 Temperature Detectors
TABLE OF CONTENTS
LIST OF FIGURES . . . . . . ii
LIST OF TABLES . . . . . . . iii
REFERENCES . . . . . . . . . iv
OBJECTIVES . . . . . . . . . . v
RESISTANCE TEMPERATURE DETECTORS (RTDs) . . 1
Temperature . . . . . . 1
RTD Construction . . 2
Summary . . . . . . . . 4
THERMOCOUPLES . . . . . 5
Thermocouple Construction . . . . . . . . . . . . . . . . . 5
Thermocouple Operation . . . . . . . . . . . . . . . . . . . 6
Summary . . . . . . . . 7
FUNCTIONAL USES OF TEMPERATURE DETECTORS . . . . . . . . . . . . . . . . . . . . . . 8
Functions of Temperature Detectors . . . . . . . . . . . . 8
Detector Problems . . 8
Environmental Concerns . . . . . . . . . . . . . . . . . . . . 9
Summary . . . . . . . . 9
TEMPERATURE DETECTION CIRCUITRY . . . . . . . . . 10
Bridge Circuit Construction . . . . . . . . . . . . . . . . 10
Bridge Circuit Operation . . . . . . . . . . . . . . . . . . 12
Temperature Detection Circuit . . . . . . . . . . . . . . . 14
Temperature Compensation . . . . . . . . . . . . . . . . . 15
Summary . . . . . . . 16
LIST OF FIGURES Temperature Detectors
LIST OF FIGURES
Figure 1 Electrical Resistance-Temperature Curves . . . 2
Figure 2 Internal Construction of a Typical RTD . . . . 3
Figure 3 RTD Protective Well and Terminal Head . . . 4
Figure 4 Thermocouple Material Characteristics
When Used with Platinum . . . . . . . . . . . . . 5
Figure 5 Internal Construction of a Typical Thermocouple . . . . . . . . . . . . . . . . . . . 6
Figure 6 Simple Thermocouple Circuit . . . . . . . . . . . 6
Figure 7 Temperature-vs-Voltage Reference Table . . . 7
Figure 8 Bridge Circuit . . . . . . . . . . . . . . . . . . . . . 11
Figure 9 Unbalanced Bridge Circuit . . . . . . . . . . . . 12
Figure 10 Balanced Bridge Circuit . . . . . . . . . . . . . . 13
Figure 11 Block Diagram of a Typical Temperature
Detection Circuit . . . . . . . . . . . . . . . . . . . 14
Figure 12 Resistance Thermometer Circuit with Precision
Resistor in Place of Resistance Bulb . . . . . 15
