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Guide to Themocouple and Resistance Thermometry

An industry leading publication since 1993 – now completely revised and updated for online use

First published in 1993, this guide has been requested by over 500,000 engineers, buyers, and specifiers. Recognised across the industry as a definitive reference, it brought together clear explanations, essential data, and practical information in one accessible wallchart.

Today, the guide is available as a fully revised and expanded online resource. Updated for 2025 and beyond, it covers the core principles of temperature measurement - including thermocouples and resistance temperature detectors (RTDs) - alongside standards, colour codes, material data, and reference charts.

Whether you’re specifying a sensor, designing a system, or training new staff, this online edition is structured for ease of use and long-term relevance, while preserving the clarity and depth of the original.

Preface

Temperature is one of the most frequently measured physical quantities in industry. The accuracy and consistency of that measurement...

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Temperature Scales

Understanding how temperature is defined is a key foundation for thermocouple and resistance thermometry...

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Thermocouples - The Basics

Thermocouples work by generating an electromotive force (EMF) in response to a temperature gradient...

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An Overview of Thermocouple Types

Selecting the right thermocouple for a given application requires careful evaluation of several factors...

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Type N - A Solution to Instability

Discover how Type N overcame the instabilities of other base metal thermocouples and give enhanced long term performance...

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Thermocouple Types in Detail

A guide to all common thermocouple types including characteristics, temperature range, standards and tolerances...

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Thermocouple Cable Tolerances & Colour Codes

Learn how thermocouple extension and compensating cables are identified and specified under IEC 60584-3...

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Power Series Expansions for Thermocouples

For computer applications, expressions are given for the commonly used thermocouple types...

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RTD's - Introduction to Resistance Thermometers

Discover the basic principles and equations that for the basis of resistance thermometry...

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RTD Sensor Materials

Explore the various materials that can be used for RTD elements from platinum to copper...

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RTD Self-Heating Effects

To measure resistance, an electrical current must pass through the RTD element. However, this current generates heat...

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RTD Standards & Tolerances to IEC 60751

The international standard IEC 60751 defines the performance and tolerance requirements for industrial RTDs...

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RTD Colour Coding and Identification

See how IEC 60751 specifies the identification and colour coding of connecting wires...

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Linearisation for Thermocouples and RTDs

Linearisation is a greater challenge for thermocouples than for resistance temperature detectors (RTDs)...

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Signal Conditioning, Interference and Isolation

Signal conditioning is critical in electronic temperature measurement, ensuring that the signal from a thermocouple or RTD...

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Temperature Transmitters and Converters

Low-level signals from thermocouples and RTDs are highly vulnerable to electrical interference and signal degradation...

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Practical Thermocouples

Thermocouples are widely used thanks to their broad temperature range, robustness, flexibility in size, and the extensive variety of...

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Thermocouple Styles

Basic forms include bare wire thermocouples with insulation suited to the environment, encased in metal or ceramic sheaths for protection...

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Thermocouple Insulation

Most real-world applications require thermocouples to be protected from the media and environment in which they are used...

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Thermocouple Cables - Operating Characteristics

An explanation of thermocouple extension and compensating cables...

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Thermocouple Connectors - Types and Styles

An introduction to thermocouple connectors and why we use them...

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Cold Junction Compensation

Thermocouples measure the temperature difference between two junctions - the measuring (hot) junction and the reference (cold) junction...

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Practical RTDs

Resistance Thermometer Detectors (RTDs) rely on platinum sensor elements that must maintain a fully annealed condition...

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RTD Element Designs

Resistance Temperature Detectors (RTDs) can be constructed in a variety of ways depending on the measurement environment....

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RTD Sensor Assemblies

Platinum RTD sensor assemblies are widely used across industries and laboratories for precise and reliable temperature measurement...

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RTD Cables

Interconnection cables for RTD assemblies come in a variety of forms, typically adhering to the IEC 60751 international color-coding...

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End Seals, Terminal Heads & Blocks

End seals, terminal blocks, and terminal heads are essential components in both thermocouple and RTD assemblies...

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Heavy Duty Industrial Assemblies

For demanding industrial environments, heavy-duty sensor assemblies offer robust protection and high-temperature performance...

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Transmitter Styles

Comparing Head Mounted, DIN Rail, and Rack Mounted transmitters...

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Digital & Smart Transmitters

Digital and smart transmitters represent the evolution of traditional signal conditioning devices for industrial temperature measurement...

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Choosing Between Thermocouples and RTDs

Selecting the right temperature sensor depends on several factors: required temperature range, response speed, accuracy...

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Measuring Thermocouple Output

Exploring legacy techniques through to modern instrumentation...

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Measuring RTD Output

Exploring application methods and equipment for accurate RTD readings...

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Siting Thermocouples and RTDs

Accurate temperature sensing depends on placing the sensor in a way that ensures it reaches the same temperature as the medium being measured...

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Installing Thermocouples and RTDs

In many applications, thermocouples and RTDs require protection from harsh environments to ensure long-term performance and accuracy...

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Averaging Thermocouples and RTDs

Thermocouples can be arranged so that their combined outputs provide an average temperature reading...

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Sensor Response Times

All temperature sensors have a finite response time — the delay between a temperature change and the sensor's output reflecting that change...

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Sensor Response Times

All temperature sensors have a finite response time — the delay between a temperature change and the sensor's output reflecting that change...

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Thermocouple and RTD Calibration

AAccurate temperature measurement depends on well-calibrated sensors. Over time, both thermocouples and resistance thermometers (RTDs) can drift...

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Troubleshooting Thermocouples and RTDs

Temperature measurement faults are often due to wiring issues, poor installation, or sensor degradation rather than sensor failure itself...

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Glossary of Thermocouple and RTD Terms

A list of terms associated with thermocouple and resistance thermometry...

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Foundational Reading

A list of seminal books, technical papers, standards, and research that formed the foundation of modern thermocouple measurement and temperature science...

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