We at Industrial Furnace & Controls manufacture Molten Thermocouple. It is the ceramic sheath which is an alloy of silicon nitride and aluminum oxide. This superior refractory material has the combined properties of silicon nitride (high strength, hardness, fracture toughness, and low thermal expansion) and aluminum oxide.

Mineral insulated thermocouples are probably the most commonly used thermocouples in industry today. They are manufactured from a seamless metal sheath. The thermocouple element is insulated from the sheath by a compacted magnesium oxide power.The temperature range is governed by the thermocouple type and sheath material.

Thomas Seeback discovered that if a circuit is formed using two dissimilar metal conductors with one junction at a higher temperature than the other then a difference in temperature creates a small current (EMF) within the circuit. The resultant EMF (Electro Motive Force) is proportional to the temperature difference between the junction and is measured in millivolt..

These flat pin miniature connectors are ideal for connecting thermocouple sensors and extension or compensating cable to each other. The pins are polarised to avoid an incorrect connection and the connector body is additionally marked for polarity. They are rated for use up to 210°C, 350°C or 650°C.
In addition to offering a plug and socket, panel sockets and 3-pin versions are also available as well as matching anodised aluminium connector panels. Weatherproof neoprene boots for added protection in moist environments and cable clamps are also available along with a wide range of accessories.

Resistance thermometers, also called resistance temperature detectors (RTDs), are sensors used to measure temperature by correlating the resistance of the RTD element with temperature. Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass core. The element is usually quite fragile, so it is often placed inside a sheathed probe to protect it. The RTD element is made from a pure material, platinum, nickel or copper. The material has a predictable change in resistance as the temperature changes; it is this predictable change that is used to determine temperature.
They are slowly replacing the use of thermocouples in many industrial applications below 600 °C, due to higher accuracy and repeatability