Thermocouple Types

Open Wire - Temprel T52 
This style is the most basic and economical.  It consists of bare or normally insulated wire with a TIG welded measuring junction and a form of connection to extension wire.  It is available in gauge sizes 20 thru 36 with a wide choice of insulation based on the application.

Sheathed - Temprel T54

This style is similar to the open wire type with the wire slid into a tube and the measuring junction exposed or welded into the end of the tube.  This allows the probe to be mounted in a compression fitting and can be liquid tight.  It is still limited to the temperature of the wire insulation.  Sizes are normally .125” diameter thru .250” diameter and the tube material can be stainless steel, glass, armor or a tightly wound spring (Boden Cable).

Sheathed MgO Filled - Temprel T21, T23, T24, T25, T26

This group shares a common probe style of a metal sheath normally .020” thru .250” diameter with compacted Magnesium Oxide insulation around the thermo-elements.  Most common sheath materials are Inconel 600; 304, 310 or 316 Stainless Steel; or Hastalloy X in single, dual or triple elements.  Since the thermo-elements are very fine and fragile, a transition to a robust termination is required, either a quick disconnect plug (T21); or a potted fitting (T25), a potted fitting with strain relief spring (for high vibration applications) (T26) to flexible 20 or 24 awg lead wires.  Special mounting fittings such as a pipe plug or oil drain plug can be welded to the sheath (T23).  Temperature limits are normally the upper operating range of the thermocouple type based on calibration and diameter (see attached chart).  The thermo-elements can also be welded into the end cap (grounded junction), exposed or electrically isolated from the sheath (ungrounded junction).

Any of the above types can be terminated with a molded on standard or mini plug 2 0r 3 prong or left open.  Open wire styles can include washers or any other type of brazed or adhesive backed mounting method. 

Standard sheath diameters             Suggested Upper Temperature Limits

                    .032”  +.001 -.0005”                            1290°F (700°C)

        .040”  +.001 -.0005”                            1290°F (700°C)

        .063”  ±.001”                                       1690°F (920°C)

        .090”  ±.001”                                       1830°F (1000°C)

        .125”  +.002 -.001”                              1960°F (1070°C)

        .188”  +.002 -.001”                              2100°F (1150°C)

        .250”  +.003 -.001”                              2100°F (1150°C)

If you don't see what you are looking for here, or if you have additional questions please feel free to contact Temprel at 1-800-582-5098.