Introduction to industial thermometry
Temperature is one of the most important and critical parameter in various process industries. Among various type of measuring instruments, RTDs and thermocouples are the most preferred choice in industrial thermometry. In order to obtain reliable sensors, it is very much important to select correct configuration sensor for a particular application. Following details will give some idea about the selection of sensor.

RTD Today there are two different type of basic RTD element available for industrial thermometry wiz thin film and wire wound. Both types have their own advantages and disadvantages.

Thin film
This type of element are manufactured by depositing thin film of Platinum on a ceramic substrate by vacuum deposition, this thin film is itched with LASER itching machine to get 100 at O C. Connecting lead is attached thereafter. Resistance so manufactured is covered with a thin layer of glass to protect the Platinum film from any disturbance.

Wire wound elements are manufactured from a thin wire of Platinum (17µ to 30µ). Size of wire is determined depending on size of element required, temperature range and long-term stability required. This wire is wound on small mandrel to make a coil. This coil is attached to a lead of bigger diameter Platinum wire. This coil is the inserted in a twin bore ceramic insulator. The resistance made is given heat treatment and trimmed to achieve a 100 at 0ºC. and filled with ultra high purity Al2O3 powder and sealed from both the sides with a glass. Below is the comparison of both the constructions of PRTD.This properties are considered while designing the temperature element.

Wire wound elements are manufactured from a thin wire of Platinum (17µ to 30µ). Size of wire is determined depending on size of element required, temperature range and long-term stability required. This wire is wound on small mandrel to make a coil. This coil is attached to a lead of bigger diameter Platinum wire. This coil is the inserted in a twin bore ceramic insulator. The resistance made is given heat treatment and trimmed to achieve a 100 at 0ºC. and filled with ultra high purity Al2O3 powder and sealed from both the sides with a glass. Below is the comparison of both the constructions of PRTD.This properties are considered while designing the temperature element.

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Mineral Insulated Metal Sheathed Thermocouple Cable
MIMS thermocouple technology has brought revolution in the TE industries as it has clear winning edge over conventional ceramic twin bore insulator T/C.

Manufacturing Process
MIMS cable are manufactured by using a higher diameter tubes and conductors. The conductors are inserted into metal pipe. The conductors are properly spaced in the pipe by using crushable MgO blocks. These MgO blocks provides insulation between the conductors as ell as with the wall. Also these blocks maintains the geometry, i.e. the position of conductors. The operation required to manufacture MIMS cable are:

• Cleaning of tubes.
• Insertion of conductor into the bocks.
• Hot filling (i.e. insertion of conductors along with the blocks into the pipe).
• Swaging (This operation crush the MgO blocks).
• Drawing (The diameter is reduced by successive drawing which also ensures compact powder around the conductors).
• Inter pass annealing (Various annealing are required to achieve the metal properties back which are disturbed in drawing. process. This annealing is conducted in controlled environment to retain the chemical properties of the sheath material).
• Testing.
• Packing and finishing.