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D38999 Thermocouple Contacts

Thermocouple Contact & Tooling Charts


Milnec Interconnect Systems manufacturers a full offering of MIL-DTL-38999 Series III high reliability thermocouple crimp contacts in the most popular thermocouple materials. By ordering thermocouple contacts separately, engineers can quickly make custom connector solutions to run power, signal, and thermocouples in one cable! In charts below you can find all the information required to order replacement thermocouple contacts for all existing MIL-DTL-38999 Series III connectors. Next to each contact is appropriate tooling information for required crimper, positioner, insertion and extraction tweezers.

Put simply, a thermocouple is a pair of wires of dissimilar metal that is connected at both ends. When the two wire junctions are exposed to different temperatures, an electrical potential is created between them that is almost directly proportional to the temperature difference. A voltage measuring instrument added to the circuit can then read the temperature. Thermocouples are made from a variety of specific alloys and are best suited for different applications depending on the intended temperature range, sensitivity, resistance to corrosion, magnetism, and cost. Because crimp connectors have removable contacts, the standard contacts can be substituted easily with thermocouples.

Thermocouple Types

Certain combinations of alloys have become popular as industry standards for thermocouples. Milnec’s standard thermocouple types are listed below with the positive electrode first, followed by the negative electrode.

Type K (chromel/alumel)

The most common general purpose thermocouple with a sensitivity of approximately 41 µV/°C, chromel positive relative to alumel.

Type E (chromel/constantan)

This type has a high output (68 µV/°C), which makes it well suited to cryogenic use. In addition, it is non-magnetic.

Type J (iron/constantan)

This combination has a more restricted range than Type K (0° to +750°C), but has a higher sensitivity (55 µV/°C).

Type T (copper/constantan)

Often used as a differential measurement. There is no Curie point and thus no abrupt change in characteristics because both conductors are non-magnetic. Range of −200° to +350°C, sensitivity 43 µV/°C.

Thermocouple Types Chart

Thermocouple Type Temperature Range (Continuous)* Temperature Range (Short Term)* Thermocouple Materials Contact Size Termination
K +32° to +2,012°F
(0° to +1,100°C)
-292° to +2,372°F
(-180° to +1,300°C)
Chromel & Alumel #16, #20, #22D Crimp
E +32° to +1,472°F
(0° to +800°C)
-40° to +1,652°F
(-40° to +900°C)
Chromel & Constantan #16, #20, #22D Crimp
J +32° to +1,382°F
(0° to +750°C)
-292° to +1,472°F
(-180° to +800°C)
Iron & Constantan #16, #20, #22D Crimp
T -301° to +572°F
(-185° to +300°C)
-418° to +752°F
(-250° to +400°C)
Copper & Constantan #22D Crimp

* Please note above thermocouple temperature ranges are for reference only. Standard connector insert materials can only withstand 392°F (200°C) of continuous operation.

Additional Resources

D38999 Series III Contact Data Sheets

  • D38999 Contacts (Power, Thermocouple, Coax, Twinax, Fiber Optic, PCB tail)
  • D38999 Catalog (15 MB) – For contact information please reference pages A-16 – A-18, and B-9 – B-14.

Thermocouple Contacts

Contact Size Contact Style Part Number Wire Size (AWG) Wire Range (Dia) Jacket Strip Length Crimping Tool Positioner Insertion Tool Extraction Tool
#22D Alumel Pin TXPA22 22, 24, 26, 28 .012–.025 (.32–.64) .157 (4.00) TK201 TP209 TN801 TX802
Socket TXSA22 TP207
#22D Chromel Pin TXPR22 TP209
Socket TXSR22 TP207
#22D Constantan Pin TXPK22 TP209
Socket TXSK22 TP207
#22D Iron Pin TXPE22 TP209
Socket TXSE22 TP207
#22D Copper Pin TXPU22 TP209
Socket TXSU22 TP207
#20 Alumel Pin TXPA20 20, 22, 24 .020–.032 (.51–.81) .197 (5.00) TK101 TP104
TN805 TX806
Socket TXSA20
#20 Chromel Pin TXPR20
Socket TXSR20
#20 Constantan Pin TXPK20
Socket TXSK20
#20 Iron Pin TXPE20
Socket TXSE20
#16 Alumel Pin TXPA16 16, 18, 20 .032–.050 (.81–1.29) .236 (6.00) TK101 TN807 TX808
Socket TXSA16
#16 Chromel Pin TXPR16
Socket TXSR16
#16 Constantan Pin TXPK16
Socket TXSK16
#16 Iron Pin TXPE16
Socket TXSE16

Dimensions are in inches (mm) unless otherwise noted.