Principles and Methods of Temperature Measurement

A. Bhatia, B.E.

Course Outline

Temperature is a principle parameter that needs to be monitored and controlled in most engineering applications such as heating, cooling, drying and storage. Temperature sensors vary from simple liquid-in-glass thermometers to sophisticated on-line monitoring and automatic temperature control purposes. This course focuses on the most commonly used temperature sensors.

This 2-hour course provides an overview of basic principles of temperature sensors in user friendly language. The theoretical equations are kept minimum and the basic aspects are discussed wherever deemed fit.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the student will be aware of:

• Learn various types of temperature sensors;
• Understand the principle of operation of thermocouples (Peltier effect, Thompson effect and Seebeck effect);
• Describe the basic construction of a thermocouple including materials used;
• Understand the three laws of thermocouples (law of intermediate metals, law of intermediate temperatures and law of additive voltages);
• Describe the difference between grounded, ungrounded and exposed junctions;
• Describe the basic principle and construction of RTD's and Thermistors;
• Understand the difference between the two main types of thermistors i.e. positive temperature coefficient (PTC) and negative temperature coefficient (NTC);
• Explain how RTD resistance varies for increase and decrease of temperatures using bridge circuits; and
• Describe the basic principles of radiative temperature measurement including infrared and optical pyrometers.

Intended Audience

This course is aimed at students, electrical & control engineers, energy auditors, O & M professionals, contractors, estimators, facility managers and general audience.

Course Introduction

Temperature sensors have been developed based on different temperature-dependent physical phenomena including thermal expansion, thermoelectricity, electrical resistance, and thermal radiation. All of them infer temperature by sensing some change in a physical characteristic. There are four basic types of temperature measuring devices, each of which uses a different principle:

1) Mechanical (liquid-in-glass thermometers, bimetallic strips, bulb & capillary, pressure type etc.)
2) Thermocouples
3) Thermo-resistive (RTDs and thermistors)
4) Radiative (infrared and optical pyrometers)

Each of these is defined and the discussed in this learning module.

Course Content

The course content is in a PDF file Principles and Methods of Temperature Measurement. You need to open or download this document to study this course.

Course Summary

Temperature measurement, a vital part of most industrial operations, is typically accomplished by a temperature sensor--a thermocouple or a resistance temperature detector (RTD)--in contact with a solid surface or immersed in a fluid. Although these sensors have overlapping temperature ranges, each has certain application-dependent advantages.

Several factors must be considered when selecting the type of sensor to be used in a specific application: temperature range, accuracy, response time, stability, linearity, and sensitivity. An RTD is the sensor of choice when sensitivity and application flexibility are the most important criteria. When it comes to component cost, an RTD is more expensive than a thermocouple. Choosing the perfect sensor for a particular application therefore requires an understanding of the basics of temperature sensors.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.