What is a thermal compensation cable?

Sascha Mais | 3. June 2020

In recent articles we have answered questions about motor, control,, servo and medium voltage cables. Today we will devote ourselves to a very special cable. The thermal compensation cable. What is a thermal compensation cable and where are these types of cables used?

Where are thermal compensation cables used?

A thermal compensation cable is the connection between a thermocouple and a measuring instrument. The thermal compensation cable must have the same materials as the thermocouple. The measurement would otherwise be distorted due to unwanted, additional thermoelectric voltages. This is also known as the Seebeck effect. The materials of the cable must be matched to the respective thermocouple type.

We find a typical application example for the use of thermocouples e.g. in injection moulding machines. During the manufacturing process of plastic parts, the temperature in the machines must be constantly monitored. This task is performed by thermocouples.

igus® production. In the injection moulding machines of the plastics manufacturer used here, thermocouples are used for temperature monitoring.

What is a thermocouple?

Thermocouples are a widely used tool in industry for temperature measurements beyond 200°C. In the simplest case, an electronic temperature measuring device consists of two components: a thermocouple as a transducer and a measuring device.

How does a thermocouple work?

A thermocouple consists of two wires of different metals. These are connected together at one end. In industrial applications, these are usually welded together, as this provides high vibration resistance.

A measuring instrument is connected to the open end of the two metals. This processes the signals of the thermocouple. The thermoelectric effect enables a voltage to be measured between the two unconnected ends. When the temperature at the measuring point rises or falls, the electron density of the two metals changes. This changed electron density can be measured at the wire ends as changed voltage.

Who invented it?

The thermoelectric effect occurs due to the temperature change. It is also known as the Seebeck effect. Thomas Johann Seebeck was a German physicist who was the first to document this effect in 1821.

The two most common types of thermocouples

It is important to know that all thermocouples are subject to an aging process. In this case one speaks of a drift. This aging process is not reversible and cannot be predicted. As a result, the measurements become less accurate over time.

There are different types of thermocouples. The various metal pairings and their measurement accuracies are defined in IEC standard 60584.

At this point I would like to briefly introduce the two most frequently used types.

Type K thermocouple:

NiCr – Ni 

Consisting of: nickel – chrome alloy/nickel

Temperature range: -40°C to +1200°C

IEC colour code: green – white

Thermocouple type J:

Fe – CuNi

Consisting of: iron/copper – nickel alloy

Temperature range: -40°C to +750°C

IEC colour code: black – white

Thermal compensation cables in energy chains:

For applications in energy chains, the chainflex® cable range includes the CFTHERMO series. These thermal compensation cables fulfil all the specifications required by the IEC standard for a thermal compensation cable.

chainflex® cables are subjected to numerous tests in the in-house test laboratory. This also applies to the CFTHERMO. K.001 which was successfully tested with over 97 million strokes in the energy chain.

Thermal compensation cables, which are used in e-chains, are found in plastic welding machines. Here the temperature at the welding tip must be closely monitored. If this temperature is too low, the workpieces cannot be joined together completely or not at all. If temperatures are too high, there is a risk that the workpieces will be deformed or damaged.

Do you have any questions about our range of thermal compensation cables? We look forward to hearing from you! We help you to find the right cable.

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