Thermocouple cable tables are essential tools for accurately identifying materials, colors, conductor cross-sections, temperature limits, and compatibility with the thermocouple type.
This guide provides a detailed explanation of how to read a thermocouple cable table, which parameters to consider, and which international standards govern these components.
What is a thermocouple cable table and what is it used for
A thermocouple cable table is a technical document that allows you to quickly identify the characteristics of a cable based on the type of thermocouple to be connected. It is used to:
- select the correct conductor material
- verify compatibility with type K, type J, B, E, N, S, T thermocouple cables, etc.
- identify insulators and sheaths suitable for operating conditions
- define the maximum supported temperature range
- avoid errors during installation
Knowing the table therefore helps prevent measurement deviations, signal interruptions, and cable deterioration.
Difference between extension cable and compensation cable
There are two main categories of cables associated with thermocouples:
Extension cable
Extension cables are designed to work at high temperatures and have one key feature: their conductors are made from the same materials as the thermocouple they are connected to. This allows the line to be extended without the risk of introducing measurement errors, maintaining stability and accuracy even when the path runs through very hot areas where a conventional cable would not be able to withstand the conditions.
Compensation cable
In compensation cables, the conductors are not identical to those of the thermocouple, but simply similar — that is, made from materials that replicate the electrical behavior of the probe within a certain temperature range. They are a more economical and flexible solution, ideal when the cable runs through areas where temperatures are moderate and a lower level of reading accuracy is acceptable.
What information does a cable table contain
A well-made technical table includes:
- conductor materials (e.g. NiCr/NiAl for type K)
- color codes for the positive, negative, and outer sheath
- conductor cross-section (e.g. 0.22 – 0.35 – 0.50 – 0.80 – 1.00 – 1.30 – 1.50 mm²)
- insulation type (PVC, silicone, PTFE, fiberglass)
- outer sheath type
- operating temperature ranges
- anti-interference shielding (tinned copper braid, polyester-laminated aluminium)
- number of pairs (single, duplex, multi-pair)
How to correctly read a thermocouple cable table
Correctly interpreting a table means reading each parameter in relation to the actual application. The elements to consider are:
- Thermocouple type: each type (K, J, B, N, S, T…) requires specific conductor materials.
- Cable cross-section: larger cross-section → lower resistance → lower losses.
- Insulation:Â essential for thermal and mechanical resistance.
- Maximum sustainable temperature:Â a critical safety parameter.
- Shielding:Â necessary when electromagnetic or electrostatic interference is present in the environment.
- Color codes:Â essential to avoid polarity reversal.
Color codes according to international standards
Each standard assigns different colors to thermocouple cables to facilitate conductor identification:
- IEC 584.3 (Germany):Â negative always white, positive varies.
- ANSI 96.1 (USA):Â negative always red.
- DIN 43714 (Europe):Â similar to IEC with minor variations.
Examples:
- Type K IEC → green/white
- Type J IEC → black/white
- Type T IEC → brown/white
This information is always shown in the cable table.
Technical parameters to evaluate when choosing a cable
When consulting a cable table, it is essential to evaluate:
- Conductor composition:Â electrical and thermal compatibility.
- Resistance per metre:Â useful for avoiding signal drops.
- Maximum temperature of the insulating material:Â PVC, silicone, PTFE, and fiberglass have very different limits.
- Outer sheath:Â resistance to oils, abrasion, moisture, and weathering.
- Shielding:Â essential in the presence of inverters, motors, or high-frequency signals.
- Number of pairs:Â chosen based on the number of probes to be connected.
- Rigidity or flexibility:Â important for mobile or fixed installation.
This comparison allows you to choose the most suitable cable for your system.
Reference standards and regulations
Thermocouple cable tables follow international standards that define:
- conductor materials
- permitted accuracy
- color codes
- thermal tolerances
The main standards are:
- IEC 60584-3:Â defines the characteristics of compensation and extension cables.
- CEI EN 60584:Â harmonized European standard.
Complying with these standards ensures electrical compatibility and consistent performance.
