Sheathed thermocouple is 'smallest in the world'

Paul Boughton
Okazaki Manufacturing Company (OMC) has developed what it claims is the world's smallest sheathed thermocouple, which has an outside diameter equivalent to that of a human hair. Launched in Japan and now available worldwide, the new super-fine thermocouple has an outside diameter of just 0.08mm, which means it is suitable 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 manufacturing, petrochemicals, oil and gas, medical, academic institutions, semiconductor manufacturing, automotive research and development, aerospace and defence.

OMC describes itself as a pioneer in temperature measurement technology and product development. Prior to this 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 believed to be 0.15mm.

With a response time of less than 1ms, OMC's latest sheathed thermocouple is suitable for measuring the temperature of virtually 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 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, comments: "We have 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 have also supplied similar units to automotive companies for the temperature profiling of diesel engines and for fuel cell research."

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