What Are Terminal Heads?
TL;DR — Quick Summary
Terminal heads (also called RTD heads or thermocouple heads) are robust enclosures fitted to the cold end of industrial temperature sensors. They house terminal blocks or temperature transmitters that link the sensor to instrumentation, while providing protection against dust, moisture, and temperature extremes. Common materials include aluminium, stainless steel, cast iron, and plastic.
What Are Terminal Heads?
Terminal heads are a type of cold-end termination used on industrial temperature sensors such as RTDs and thermocouples. They form the protective housing at the non-measuring end of the sensor, where electrical connections are made and signals are transferred to control or monitoring systems.
Inside a terminal head, you will typically find:
- Terminal blocks — for direct wiring connections
- Temperature transmitters — for converting sensor signals to standardised outputs (e.g., 4–20 mA or digital protocols)
Why Use a Terminal Head?
- Environmental Protection
- Shields the sensor connections from dust, moisture, and contaminants.
- Often designed with high ingress protection (IP) ratings.
- Temperature Resistance
- Suitable for harsh process environments.
- Protects sensitive electronics from heat damage.
- Ease of Maintenance
- Allows quick access to wiring or transmitters for servicing or calibration.
Materials Used in Terminal Heads
- Aluminium — the most common choice, offering strength, corrosion resistance, and good heat tolerance.
- Stainless Steel — for hygienic or highly corrosive environments.
- Cast Iron — for heavy-duty industrial settings.
- Plastic — lightweight and corrosion-resistant, ideal for non-extreme environments.
Common Terminal Head Designs
Industry-standard models include:
- KNE — rounded aluminium design with a screw-on cap.
- ALA — larger style with more wiring space.
- BUZ — compact and robust, widely used in process industries.
Frequently Asked Questions (FAQ)
What’s the difference between a terminal head and a connector?
A terminal head is a protective enclosure housing electrical connections and sometimes transmitters, while a connector is a simple plug-and-socket system for quick disconnection.
Can terminal heads be used outdoors?
Yes — many terminal heads have high IP ratings for weatherproofing, making them suitable for outdoor and washdown areas.
Do I always need a temperature transmitter inside the terminal head?
Not necessarily — if you’re wiring the sensor directly to instrumentation, a terminal block may be enough. Transmitters are used when you need signal conditioning or long cable runs.
Are terminal heads interchangeable between RTDs and thermocouples?
Yes, the enclosure itself is compatible, but the internal wiring, connectors, and transmitter configuration will vary depending on the sensor type.
How do I choose the right terminal head material?
Consider environmental factors such as corrosion, temperature, hygiene requirements, and mechanical impact risks.
If you want to order a temperature sensor or you are unsure exactly what you need, get in touch and we can help you.