Thermocouple Connectors Explained – All You Need To Know

Thermocouple connectors are essential to many scientific and industrial applications in industries such as mining, steel, petroleum, aerospace, food and beverage, power generation, pharmaceutical, and more.

These connectors transmit temperature readings and voltage values from a thermocouple (T/C) to a host meter or computer. Thermocouple connectors are made of various materials depending on the temperature demand and are color-coded for ease of operation. Different pin types are available, and each connector style meets the requirements for specific applications.

Here you’ll learn the basics about thermocouple connectors, including the most popular types and why they have certain specifications.

What Is a Thermocouple Connector?

Thermocouple connectors are an invaluable tool for reporting temperature readings from a T/C. They are specifically rated for certain temperature ranges and can extend the thermocouple wire, ensuring the T/C lead wire or sensor accurately transmits the temperature measurement signal in millivolts to the control instrumentation or display.

An appropriate thermocouple connector must be attached to the proper T/C terminal for each type of thermocouple wire. The connector ground protects against electrical noise and the errors they may cause.

Some products utilize an external group strap to strengthen the mechanical link between the connectors and maintain the electrical connection of the ground wire. Wireless thermocouple connectors are also an option.

What Are Thermocouple Connectors Made Of?

A thermoelectric effect occurs when two conductive materials make contact and form a thermal junction. Metallic alloys are suitable for use in thermocouple manufacturing because of their ability to make the proper connection.

The thermocouple contacts in the connector have to match precisely with the thermocouple lead wires or sensor. If the thermocouple connector cannot hold a uniform temperature, T/C grade alloys incorporated into the contact points eliminate unwanted EMFs.

There are some crucial characteristics to consider when selecting T/C material:

  • Maximum sensibility over the operating range
  • High-temperature capabilities
  • Long-term stability
  • Cost
  • Compatibility with available instrumentation

Most metallic thermocouple materials have two or more components to achieve the desired temperature characteristics. Other commonly used materials for thermocouple connectors include:

  • Thermoplastics: The most typical thermocouple connectors consist of thermoplastics that can withstand temperatures up to 400 °F and supply a sufficient level of mechanical durability.
  • Thermosets: Manufactured using thermoset materials, they are a good choice for applications that require continuous exposure to temperatures up to 660 °F. These types of connectors may crack more easily than thermoplastic connectors, but they have better impact resistance compared to ceramics.
  • Ceramics: Thermocouple connectors made from ceramics offer the highest temperature capabilities, up to 1200 °F. Ceramic connectors are effective in vacuum applications since the potential for contamination or outgassing does not exist. Compared to thermoplastic or thermoset designs, ceramic connectors are more susceptible to mechanical damage.

The capabilities of the T/C connector material and the thermocouple alloy pins are essential when determining the proper temperature measurement application.

Why Are Thermocouple Connectors Color-Coded?

Thermocouples are color-coded and classified by letters depending on their level of approval. North American products carry the Underwriters Laboratories UL mark. European products comply with the EU directive RoHS, which states all manufacturers must demonstrate their products contain minimal hazardous substances. Connector bodies are color-coded per ANSI MC96.1 thermocouple standards.

Consistent labeling helps differentiate which type of T/C wire you need to order, with established color codes to ensure proper identification. All T/C types have associated colors. Extension grade and standard grade wires have their own colors, while negative and positive leads have differing colors.

There are some exceptions to the USA ANSI standards when matching the connector color to the associated wire. The connector body color matches the color of the insulation on the positive wire, except when using Type J calibration.

Higher temperature rated components are brown or white, depending on the maximum temperature. The bodies are marked with a letter to avoid confusion. Thermocouple grade wire has a brown exterior insulated jacket for wire pairs with T, E, K, J, and N calibrations. The thermocouple connector colors are:

  • T = Blue
  • E = Purple
  • K = Yellow
  • J = Black
  • N = Orange

Extension grade thermocouple wires have USA insulation colors that match the body color of the connector.

  • Type K
    • Thermocouple Grade Jacket: Brown
    • Extension Grade Jacket: Yellow
    • Positive Lead: Yellow
    • Negative Lead: Red
  • Type J
    • Thermocouple Grade Jacket: Brown
    • Extension Grade Jacket: Black
    • Positive Lead: White
    • Negative Lead: Red
  • Type N
    • Thermocouple Grade Jacket: Brown
    • Extension Grade Jacket: Orange
    • Positive Lead: Orange
    • Negative Lead: Red
  • Type R & S
    • Thermocouple Grade Jacket: No color specified
    • Extension Grade Jacket: Green
    • Positive Lead: Black
    • Negative Lead: Red
  • Type T
    • Thermocouple Grade Jacket: Brown
    • Extension Grade Jacket: Blue
    • Positive Lead: Blue
    • Negative Lead: Red
  • Type E
    • Thermocouple Grade Jacket: Brown
    • Extension Grade Jacket: Purple
    • Positive Lead: Purple
    • Negative Lead: Red

Include Chart: https://www.thermocoupleinfo.com/thermocouple-color-codes.htm

Most Utilized Thermocouple Connectors

The most commonly used thermocouple connectors are constructed from thermoplastics due to the broad temperature range of -40 °F to 400 °F. Sometimes called base metal thermocouples, J, K, T, E, and N calibrations are the most utilized designs. Type C and R/S thermocouples are more common in higher temperature applications.

There is an extensive range of styles for various applications, rated for use up to 425 °F, 660 °F, and 1200 °F.  Available thermocouple connector versions include:

  • Plug and jack
  • Panel jacks
  • Multi-pin designs
  • Flat or round pins
  • Miniature and standard sizes
  • Quick connect and disconnect

Matching anodized aluminum connector panels and weatherproof neoprene boots offer added protection in damp environments.

Pin Types

Standard thermocouple connectors have round polarized pins, and the connector body is marked for negative and positive polarity to avoid an incorrect connection.

Connectors have a number of pins specifically designed to complement the measurement circuit of the temperature sensor or T/C. The most popular configurations are:

  • 2-Pin: Used with a single-circuit temperature sensor, this is the most popular connector style.
  • 3-Pin: Three-pin connectors help minimize electrical signal interference. One pin is copper ground. The configuration with all three copper pins is common with single-circuit three-wire RTD temperature sensing use cases.
  • 4-Pin: Used for two thermocouple circuits or with a single-circuit 4-wire RTD temperature sensor, four-pin connectors are also known as dual connectors.
  • Multi-Pin: Multi-pin configurations provide connections from one temperature measurement circuit up to 24 circuits with or without signal connections.

Thermocouple Connectors Specifications

  • Operating Temperature: -54 to +982 °C (-65 to +1799 °F)
  • Features & Applications
    • Commercial & amp
    • Nuclear
    • Laser and X-ray equipment
    • Low outgassing for space and vacuum applications
    • Hermetically sealed interconnects
    • High and/or low voltage
    • High temperatures to +250 °C
    • High current up to 1000 amperes

Thermocouple Connectors From Connectronics

Since 1988, Connectronics Corp. has been designing and manufacturing specialized connectors and interconnection systems. With over 300 combined years of experience in designing and manufacturing connectors for instrumentation, medical, aerospace, avionics, nuclear, and other industries, the Connectronics team has a proven ability to produce reliable, high-performance interconnections for the most demanding applications.

We are ISO 9001:2015 and AS9100D certified and follow Supplier Quality Assurance Requirements (SQAR) on all purchase orders. Our designs meet the established requirements for safe and effective operation and extended service life.

Connectronics utilizes state-of-the-art environmental test equipment for helium leak detection, thermal shock, altitude, and humidity analysis. These tests guarantee you receive corona-free thermocouple connectors that meet all demands of your application.

Contact Connectronics to discuss your specific business needs, or request more information about the products we offer.