Thermocouples | Resistence Thermometers | Thermistor Probes | Hand Held Sensors

What is a Thermocouple?
T.J. Seeback in 1821 observed that a small electric current flows in a closed circuit of two dissimilar metals if one of the junctions is heated with respect to the other. ( this is known as the Seeback effect).

Reversing the heating polarity produces an opposite direction of current flow. The magnitude of the voltage generated, called the electromotive force (e.m.f) is a function of the temperature difference of the two junctions.

Although many combinations of metals and alloys display thermocouple behaviour, in practice only a small number meet the general requirements of industrial and laboratory applications. The small thermal e.m.f (thermocouple signal) produced must be of sufficient magnitude, linearity and repeatability for use by conventional instrumentation as a measured quantity.

For practical purposes, thermocouples are divided into two categories: noble metal types (usually Platinum V Platinum Rhodium) and base metal types such as Nickel Chromium V Nickel Aluminium (Type K) and Iron V Copper Nickel (Type J). Measuring junctions are formed by welding the two dissimilar wires usually located inside a protecting sheath.

General Use	General Use Fabricated
Plastics Thermocouple	Thermocouple Connectors