Mineral Insulated Thermocouples & RTDs
Mineral insulated thermocouples and RTDs represent the second generation of temperature sensors developed around the 1980s, based on conventional assembled thermocouples and RTDs. They mark a major technological breakthrough in the history of thermometry.
Compared with conventional assembled types, mineral insulated sensors feature smaller diameter, better sealing performance, excellent flexibility, fast thermal response, high reliability, lower cost, suitability for mass production, and ease of use.
Material Structure
The core component is often referred to as "thermocouple cable" or "MI cable", officially named mineral insulated thermocouple cable. For mineral insulated platinum RTDs, it is also called "platinum resistance lead wire".
It integrates the three basic elements of a temperature sensor - thermocouple wires or RTD elements, high-grade insulation material, and protective sheath - into a compact, flexible, non-detachable solid structure through repeated drawing and diameter reduction.
The protective sheath is typically made of stainless steel, high-temperature alloy, or other metallic materials.
Mineral insulated thermocouples: generally ф0.5–8.0 mm in diameter
Mineral insulated platinum RTDs: generally ф3.0–8.0 mm in diameter
All standard thermocouple and RTD types can be manufactured in mineral insulated form.
Structure Types & Applications
Structurally, they still consist of a measuring end, transition section, and connection end. The MI cable is cut to the required length, after which the measuring tip and terminal assembly are fabricated, along with mounting fixtures and connection heads.
Single mineral insulated elements can reach up to 20 meters in length or even longer. They are available in three main types:
Standard type
Extension tube type
Insert type for assembled probes
Extension tube type mineral insulated sensors are often used with thermowells to allow replacement of the sensing element without shutting down the equipment.
Mineral insulated thermocouples and RTDs can replace conventional assembled sensors in most applications. They are widely used for temperature measurement in machinery, chemicals, aerospace, energy, building materials, pharmaceuticals, food processing, and other industries.
Typical applications include electric furnaces, ovens, tanks, vessels, pipelines, combustion heating systems, and various physical and chemical reaction processes.