World’s Smallest Thermocouple

29 July 2009

Okazaki Manufacturing Company (OMC), a manufacturer of high accuracy temperature measurement products, including thermowells, mineral-insulated thermocouple and RTD cable, has developed what it claims to be the world’s smallest sheathed thermocouple, which has an outside diameter equivalent to that of a human hair.

comparing thermocouple to mechanical pencil
comparing thermocouple to mechanical pencil

It was launched this past summer in Japan and is now available worldwide. The super-fine thermocouple has an outside diameter of just 0.08mm, which means it is ideal for use in applications where space is restricted. The thermocouple can also be bent on installation without causing damage or loss of performance.

Sheathed thermocouples are used in a wide range of temperature sensing applications, including process manufacturing, petrochemicals, oil and gas, medical, academic institutions, semiconductor manufacturing, automotive R&D, aerospace and defence.

OMC considers itself a pioneer in temperature measurement technology and product development. Prior to this latest product launch, OMC’s previous smallest diameter sheathed thermocouple had an outside diameter of 0.10mm. The smallest outside diameter sheathed thermocouple currently available on the market from an alternative supplier is 0.15mm.

OMC says the thermocouple has an “incredible response time of less than 1ms” and is
suitable for measuring the temperature of any small object or material. An outside diameter of 0.08mm means that the thermocouple element wires need to be extremely fine. In order to form the hot junctions, OMC says it has developed “highly advanced manufacturing technology” at its plants in Japan.

A sheathed thermocouple typically comprises a metal sheath with thermocouple elements inside that are tightly packed with mineral powder. The mineral powder insulates the thermocouple elements from one another and from the sheath. The smaller the diameter or mass of a sheathed thermocouple, the faster the thermal response time will be.

Chris Chant, Business Development Manager at OMC commented: “We’ve supplied sheathed thermocouples for all kinds of unusual applications, particularly where space restrictions mean the customer requires a small diameter solution.

“For example, we recently supplied thermocouples to a defence company, who installed the units in the exhaust manifold of a battle tank. We’ve also supplied similar units to automotive companies for the temperature profiling of diesel engines and for fuel cell research.”

For more information on OMC’s range of sheathed thermocouples and other temperature measurement products, please visit the website at

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