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Products > Temperature > Temperature Measurement > Mineral Insulated Thermocouples
A metal sheathed cable with thermocouple conductors which are insulated from each other and the sheath by highly compacted magnesium oxide.
Conductors are safe from environmental contamination, ductile and highly responsive.
The cables are water, oil and gas resistant, extremely robust and are eminently suitable for applications where high or low temperature, corrosion, vibration, pressure and other extreme conditions exist.
Advantages of Mineral Insulated Thermocouples:
- Rapid response - due to small thermal capacity of conductor bead and high thermal conductivity of insulant.
- Ductile - can be easily bent or formed.
- Completely immune from thermal shock.
- Small overall diameters.
- Very high insulation resistance.
- Unaffected by pressure - can be glanded through bulkheads or pressure vessel walls.
- Extensive range of diameter, conductor and sheath combinations.
- Available in simplex or duplex options.
- Can be used in standard units in place of insulated wire elements.
Standard Metal Sheath Materials
TYPE S
18/8/1 Stainless Steel / Chrome / Nickel / Titanium Grade 321
Excellent resistance to corrosion. Retaining good ductility in a wide range of industrial applications. Max temperature 800°C
TYPE W
25/20 Stainless Steel / Chrome / Nickel Grade 310
Good high temperature corrosion resistance. Suitable for use in sulphur bearing atmospheres but should not be subjected to subsequent manipulation. Max temperature 1100°C
TYPE I
76/16/7 Inconel / Nickel / Chrome / Iron type 600
Excellent corrosive and oxidation resistant at elevated temperatures. Should not be used in Sulphur bearing atmospheres above 550°C Max temperature 1100°C
TYPE N
84/14/1 Nicosil / Nickel / Chrome / Silicon
Used with type N conductors for 1200°C plus. High oxidation resistance reduces calibration drift at temperature when used in non-carburising atmospheres. Max temperature 1250°C
Sheath Diameters
| Available Sheath Materials | |||||||||
| T/C Type | Materials | ||||||||
| T | - | S | S | - | S | S | - | S | - |
| N | - | I,N | I,N | I | I,N | I | - | I,N | - |
| J | - | S | I,S | I,S | I,S | I,S | - | I,S | I |
| K | I,S | I,S,W | I,S,W,N | I,S,W | I,S,W,N | I,S,W | I,W | I,S,W,N | I,W |
| Cable Diameter | 0.5 | 1.0 | 1.5 | 2.0 | 3.0 | 4.5 | 5.5 | 6.0 | 10.8 |
Key: I = Inconel N = Nicrosil W = 25/20 S = 18/8/1
Conductor Materials
Conductors and sheaths are welded using a fully automatic capacitance - arc welder with an inert atmosphere ensuring complete homogeneity of welds.
| Conductor and Sheath Materials | ||
| T/C Type | Conductor Combination | Recommended Temperature |
| K | Nickel Chrome vs Nickel Aluminium | 0 to 1100°C |
| J | Iron vs Constanton | 0 to 750°C |
| T | Copper vs Constanton | -200 to 300°C |
| N | Nicrosil vs Nisil | 0 to 1250°C |
All thermocouples are manufactured to the relevant BS EN 60584-1 with tolerances to BS EN 60584-2.
Figures should be used in conjunction with maximum operating temperature for metal sheath material. Other conductor combinations are available.
Cold End Seals and Terminations
- Threaded Pot crimped-on. 8mm ISO - up to 3mm Diameter MI
- Plain Pot crimped-on. 7mm diameter - up to 3mm Diameter MI
- Plain Pot crimped-on. 11mm diameter - up to 6mm Diameter MI
- Plain Pot crimped-on. 9.5mm diameter x 25mm long
- Special seals to customer requirements
- Plain Pot. For thick wall MI
- Miniature Plug or socket. Flat Pin
- Standard plug or socket. Round pin, available also in ceramic.
- Termination Head Angle Entry. Other types are available. 16mm Cable entry. Moulded Hand Grip.
Cold end sealants available to cover temperature range of –105°C to 300°C. High temperatures can be covered with cement type seals. Standard tails are flexible 75mm long with PTFE covering. Special tail wire can be supplied i.e. with fibreglass, PVC, metal braided coverings etc.