The thermocouples that can be used for this purpose are as versatile as your applications. In measurement and control technology and in the control of processes and systems, correctly recorded temperatures are crucial for the trouble-free operation of the systems. Thermocouples are always used when the temperature needs to be measured particularly quickly or when a large measuring range with sometimes very high temperatures is required.
For further information on contact temperature measurement, please click here.
We have compiled this guide to help you choose, purchase, install, and operate your contact thermocouple.
What is a contact thermocouple?
Our contact thermocouples are used wherever temperatures on the surface of pipes or metal components need to be measured – for example, on the flow and return lines of heating systems, on heat pumps, or in industrial plants. Precise measurement of these temperatures is crucial for the efficiency and control accuracy of the entire system. If the flow temperature is too low, the room remains cold; if it is too high, energy is wasted.
The heart of a contact thermocouple is its type: it enables optimal thermal coupling to the measuring point, ensuring reliable and fast measured values.
Each application places different demands on the shape, material, and cable, which is why we offer a wide range of types to maximize the contact surface and minimize the response time.
Please note the following points when making your selection
- What is the measuring range, i.e., in which temperature range should the measurement take place?
- What is the ambient temperature?
- What other environmental conditions prevail (humidity, steam, pressure, vibration?)
- In which medium is the measurement to be taken?
- How is the temperature probe to be attached to the process?
- How much space do you have for installing the probe?
What different types of contact temperature probes are available?
We offer our contact thermocouples in different types – each available as Type J or Type K, and in combination with PVC, silicone, PFA or glass fibre cables.
The following variants are available:
Each type is available with the standard cables:
- PVC cable – flexible and economical, for moderate temperatures
- Silicone cable – particularly flexible, heat-resistant up to approx. 180 °C
- PFA cable – chemical-resistant and temperature-resistant up to approx. 260°C
- Glass fiber cable – for very high ambient temperatures up to approx. 400°C
All versions are designed so that they can be efficiently mounted on the surface, offer a fast response to temperature changes, and deliver reliable measured values – even under demanding conditions.
What do I need to consider when selecting the right contact thermocouple?
The selection of the right contact thermocouple depends directly on your measurement task and the ambient conditions. Typical questions we hear from our customers:
- Is the thermocouple compatible with my measuring device?
- Which thermocouple type is the right one – type J or type K?
- Is the cable material suitable for my application?
- Which type is best suited for my application?
- Do I need to pay attention to certain influences such as temperature, humidity, or chemicals?
The following criteria will help you make the right choice:
- Which thermocouple type is suitable?
- We offer our contact probes as thermocouples type J and type K: Please check the operating instructions for your measuring device to see which thermocouple type is supported. Type J and type K cannot be interchanged – they deliver different voltages and are not compatible.
- Type K (NiCr-Ni): The most commonly used type, can be used up to +1000°C, very robust and resistant to oxidation.
- Type J (Fe-CuNi): Good for lower temperature ranges up to approx. +750°C, but more sensitive to oxidizing atmospheres.
- Is the thermocouple suitable for the required temperature range? In addition to the thermocouple type, the ambient temperature is also decisive. Not only the measuring element itself, but also the cable and insulation used must withstand the temperature requirements: Also consider factors such as heat exposure on the surface, radiation influences or contact with hot components.
- PVC: up to approx. +105°C
- Silicone: up to approx. +180 °C
- PFA: up to approx. +260 °C
- Glass fiber: depending on the design, up to over +400 °C
- Which type is right for the application? The type of contact thermocouple determines how well the temperature can be transferred and measured. The following options are available: Select the type so that the largest possible contact surface and a secure fit are ensured. This increases the measuring accuracy and shortens the response time.
- Tube contact thermocouples – attached directly to the tube
- With contact block – for flat contact
- With ring or cable lug – for stable mounting
- Angle thermocouples – for limited space or difficult access
- What is the mechanical environment like?In addition to temperature and medium, also consider other mechanical and chemical stresses:These factors influence the choice of wire type, insulation, housing, and mounting.
- Moisture/splashing water (IP protection)
- Steam or aggressive gases
- Mechanical vibrations or movement
- Space conditions at the installation site
- What must be considered during installation?Correct thermal coupling is crucial for accurate measurement. The contact surface should be clean, flat, and easily accessible. In many cases, the use of thermal conduction paste can significantly improve heat transfer. Depending on the type, additional mounting material such as clamps, quick-release straps or fastening screws may be required.
- Required accessories
- Before ordering, please check whether cables, connectors or fastening materials are included or are required additionally. Suitable accessories can facilitate installation and improve measurement reliability.
Replacing a defective thermocouple
If a contact thermocouple is defective, special care must be taken when replacing it – especially when selecting the correct thermocouple type and the appropriate type.
Please note: Thermocouples are not compatible with each other. Type J and type K differ in material, measuring principle, and signal voltage. An incorrect thermocouple type will result in incorrect measured values or render the measurement unusable. Therefore, check the operating instructions for your measuring device or the system to determine which thermocouple type may be used. If in doubt, contact the manufacturer of the system.
Once you have determined the correct type, make sure that the mechanical connection is correct. Reliable temperature measurement can only be guaranteed if the new thermocouple can be properly attached to the intended location, e.g., with a ring, mounting block, or cable lug. An inaccurate fit can lead to measurement deviations or malfunctions in the entire system.
Don't forget to order thermal conduction paste or the necessary mounting accessories, such as quick-release straps, screws, or brackets. Thermal conduction paste often significantly improves the response behavior and measurement accuracy, especially when thermally coupling to surfaces.
Frequently asked questions about contact thermocouples
The temperature probe is displaying unusual values – what could be the cause?
Inconsistent or fluctuating measured values are a common sign of problems with thermocouples. Possible causes are:
- The thermocouple type (e.g. type J or type K) does not match the measuring device
- The probe is connected with the wrong polarity (plus/minus reversed)
- The probe is not mechanically correctly attached to the surface
- Interference from electromagnetic influences (e.g. from motors or frequency converters)
The temperature probe does not display any values – what should I do?
If no values are displayed, there is often a signal interruption, a cable break, or an incompatible connection. Check the following:
- Are the connection cables correctly connected?
- Does the plug assignment match that of the measuring device?
- Is the thermo plug (if present) intact?
How can I check whether the thermocouple is defective?
Thermocouples generate a millivolt signal that is temperature-dependent. This can only be checked with a suitable measuring device or multimeter with a thermocouple input. Standard multimeters without an mV measurement function are not sufficient for this.
Alternatively, you can connect an identical thermocouple for testing purposes. If the values are correct, there is probably a defect in the original probe.
How do I connect a thermocouple correctly?
Make sure the polarity is correct: Thermocouples have a defined positive and negative side. Mixing them up will result in incorrect or unstable readings. The colors of the wires vary depending on the standard (IEC or ANSI) – please refer to the labeling on the type plate or in the data sheet.
In addition, only suitable thermocouple cables or compensation cables that match the thermocouple type should be used. Incorrect cable material can lead to significant measurement errors.
