Mineral-Insulated resistance thermometers (M.I.) are equipped in general with Platinum-measuring resistors Pt100 O to DIN IEC 751. The inner (Cu) conductors are embedded in a closely compacted, inert mineral powder (MgO); the measuring resistor will be connected to the inner conductors, is also embedded and is surrounded by the metal sheath to form a hermetically sealed assembly. Sometimes inner conductor of constantan and nickel are also used.
The sheath functions as a useful protective cover in many situations. They are applied in locations where fast response, reduced space and or vibration resistance is a need. They can be furnished with a fixed cable or with a special plug which allows rapid fitting or exchange.
Mineral-insulated RTD temperature probes consist of a flexible, thin-walled stainless steel mineral insulated cable, in which low ohmic conductor copper wires are embedded in pressed, heat resistant magnesium oxide.
The temperature probe is connected to the wires of the internal conductors and accommodated in a stainless steel sheath. Thermowell and mineral-insulated cable are welded to one another.
The good heat transition between the sheath and the temperature probe permits short response times and high measuring accuracy. The vibration resistant (shake proof) design guarantees a long operating life.
Temperature measurements at measuring points difficult to access are possible thanks to the flexible mineral-insulated cable. The smallest bending radius is 5 times the outer diameter.