End Seals, Terminal Blocks and Terminal Heads

End seals, terminal blocks, and terminal heads are essential components in both thermocouple and RTD assemblies, ensuring protection, signal integrity, and mechanical robustness. These components are selected based on factors such as temperature range, environment, installation requirements, and sensor type.

End Seals

End seals prevent moisture ingress and provide mechanical protection where sensor conductors exit the sheath. They are available in a wide variety of forms to suit different applications:

• Epoxy Resin Seals:
  Standard RTD and thermocouple sensors may be supplied with bare end conductors and internal epoxy resin sealing. These are suitable for temperatures up to 150°C, while high-temperature resins can extend this range up to 300°C.
• Glass and Resin Seals:
  Designed for more extreme applications, these seals can withstand temperatures of up to 600°C and are commonly used in higher temperature thermocouple assemblies.
• Crimped Stainless Steel Pot Seals:
  Available in threaded or unthreaded designs, these are potted with epoxy or resin materials and offer the same temperature ratings as above and are generally used to transition to extension cable. Some versions include anti-chafe spring tension fittings for added strain relief and mechanical protection.
• Compression Gland Pot Seals:
  Constructed from brass or stainless steel, these provide a more secure and rugged seal, especially useful in industrial environments where vibration or pressure is a concern.

Terminal Blocks

Terminal blocks provide the electrical connection point between the sensing element and the external wiring. These are typically housed within terminal heads and are available in a variety of materials, including ceramic (porcelain) for high-temperature applications and plastic for standard environments.

Terminal Heads

Terminal heads protect the sensor terminals and provide a secure housing for connection blocks. These are designed for harsh industrial environments and come in various styles and materials:

• Basic Die-Cast Heads:
  Commonly made from aluminum alloy, these include a screw-on lid with gasket for environmental sealing, a ceramic connector block, and cable pinch glands. These are often used in single-channel or duplex sensor assemblies.
• Straight-Through Design:
  In simpler installations, straight-through designs allow for a direct cable path through the terminal head. These are suitable for applications with limited space or straightforward wiring requirements.
• Right-Angle Entry/Exit Heads:
  More commonly used in industrial applications, these designs feature the sensor entry and cable exit at 90° to each other. This configuration improves strain relief and helps organize cable routing in tight or complex installations.

Further Reading

RTD vs Thermocouple – Choosing the Right Sensor
Explore the features and characteristics of thermocouples and RTDs

RTD Output Tables
View Resistance versus Temperature tables for all Pt100 sensors.

What are the RTD colour codes?
Explore RTD colour codes and wiring configurations.