Temperature Sensor Basics: Thermocouples

Industrial style thermocouple
(Duro-Sense)

Industrial thermocouples are used for a very broad range of temperature sensing applications. They are inexpensive, accurate, and can be fabricated in many forms to meet the requirements of the process. They operate on the "Seebeck Effect" which is the phenomena of dissimilar metal conductors producing a measurable voltage difference between two substances.

Thermocouples are used widely in industrial processes in industries such as power generation, primary metals, pulp and paper, petro-chemical, and OEM equipment. They can be fabricated in protective wells, and can be housed in general purpose, water-tight, or explosion-proof housings.

Thermocouple types - such a type J, type K, type R, and type S - refer to the alloy combinations used for the conductors and are based on standardized color designations.

The following video provides a basic visual understanding of thermocouple wire, how a T/C junction is determined, and also discusses thermocouple connectors, polarity and some aspects of construction (such as grounded vs. ungrounded vs. open tip).

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Thermocouple Basics

Type K thermocouple diagram

A thermocouple is a temperature sensor that produces a micro-voltage from a phenomena called the Seebeck Effect. In simple terms, when the junction of two different (dissimilar) metals varies in temperature from a second junction (called the reference junction), a voltage is produced. When the reference junction temperature is known and maintained, the voltage produced by the sensing junction can be measured and directly applied to the change in the sensing junctions' temperature.

Thermocouples are widely used for industrial and commercial temperate control because they are inexpensive, fairly accurate, have a fairly linear temperature-to-signal output curve, come in many “types” (different metal alloys) for many different temperature ranges, and are easily interchangeable. They require no external power to work and can be used in continuous temperature measurement applications from -185 Deg. Celsius (Type T) up to 1700 Deg. Celsius (Type B).

Welcome to the Duro-Sense Blog

Welcome! We hope (over time) you find this blog interesting to visit and it becomes a trusted resource for all-things-temperature-measurement.

We plan on weekly educational and informative blog posts about innovative temperature sensor solutions, insight to how sensors work, and new products that solve tough engineering challenges.

Specific products we'll be discussing are:

• Thermocouples
• RTDs
• Thermowells
• Sensor Accessories

Please come back often!