Metal sheathed thermocouples are allowing small bending radii and are generally used in tight spaces with difficult access to the location. The thermocouples are embedded by a compressed oxide powder in a mineral insulated mantle and therefore resistant against vibrations. The measured values are not influenced either by bending or by strong vibrations.
The application spectrum of mantle thermocouples is quite varied. Because of their high temperature resistance these sensors are used for measurements in harsh industrial applications. They guarantee exact temperature measuring on the surfaces of containers, pipelines, apparatuses and machines, in laboratories or in experimental plants, in gaseous media such as air, gases and in fluid media such as water or oil and in low and high pressure environments with low flow speeds.
In the thin walled mantle tube (wall thickness is about 125 to 15% of mantle diameter) one or two thermocouples (depending on diameter) are tightly pressed into ceramic powder.
In standard form the thermal wires are insulated against each other and against the mantle. For special models the measuring point can be welded into the mantle. This shortens the response times, especially in gases, though the mantle jacket degrades faster through corrosion. The thermal voltages are in conformity with the standard IEC 60584, class 2, and DIN 43710. The mantle material is stainless steel M.-No. 1.4541 for temperatures up to 850 °C or Iconel® M.-No. 2.4816 for temperatures up to 1100 °C.
Metal sheathed thermocouples are available in different versions: with bare or reinforced and insulated thermal wire ends, with permanently attached extension grade wires, with thermal plugs, with socket, with connector head (for example DIN connection head in form A or B). Two essential design differences: insulated welded and not insulated welded.