How is a sheathed cable constructed?

The construction of a sheathed cable consists of an outer sheath of metal, two to eight inner conductors (whose material is determined based on the field of application) and an insulation.

How are sheathed cables insulated?

The insulation of sheathed cables consists of highly-compressed metal oxide powder (preferably MgO or Al2O3).

What material are the inner conductors of sheathed cables for thermocouples?

Sheathed cables for thermocouples consist of inner conductors made of thermocouple material.

What material are the inner conductors of sheathed cables for resistance thermometers?

Sheathed cables for resistance thermometers have inner conductors of copper, copper-nickel alloy, nickel, nickel-chrome or nickel-plated copper.

Which sheathed cables are offered?

We offer a wide programme of sheathed cables for the manufacture of sheathed thermocouples and sheathed resistance thermometers. All standardised thermocouples of the types K, J, L, T, U, E and N, as well as the noble metal thermocouples types R, S and B can be delivered as sheathed thermocouple cables. Also, various sheathed cables with Cu, CuNi, Ni and NiCr inner conductors are available from stock.

Can sheathed cables be made in special designs?

Sheathed cables can be manufactured in special designs. We are able to meet your specific requirements. Please do not hesitate to contact us.

Can I order with the standard order numbers printed in the catalogue?

When it comes to the standard order numbers printed in the catalogue for special versions, these are not deliverable from stock. With a minimum order quantity (one production length) and a minimum production time, we can produce these for you.

What is the delivery time for sheathed cables?

If you place your order by 11 a.m. on a working day, for in-stock sheathed cables, the order can be processed and shipped on the same day.

What lengths and diameters are offered for sheathed cables?

The production lengths of sheathed cables depends on the lengths of the original tubes. We offer the following lengths:
  • 0.50 mm 4,500 m
  • 1.00 mm 1,200 m
  • 1.50 mm 3,600 m
  • 1.60 mm 3,300 m
  • 2.00 mm 2,100 m
  • 3.00 mm 920 m
  • 3.20 mm 800 m
  • 4.50 mm 410 m
  • 4.80 mm 360 m
  • 6.00 mm 230 m
  • 6.40 mm 200 m
  • 8.00 mm 130 m
  • 9.52 mm 80 m

Which standards do sheathed thermocouple cables fulfil?

Our sheathed thermocouple cables comply with the DIN IEC 61515 standard as well as the requirements of ASTM E 585. Special tests in accordance with ASTM 585 must be explicitly agreed when the order is placed.

How are the geometries of sheathed cables oriented?

The geometries of sheathed cables are based on the dimensions of the DIN IEC 61515 and ASTM E 585 standards.

Can special geometries of sheathed cables be offered?

In addition to the geometries of sheathed cables, we offer a specific portfolio of special geometries that have been adapted to specific customer needs.

What is the minimum order value for an order?

The minimum order value of an order is 300 euros. For orders under 300 euros, we charge the difference up to 300 euros. Individual solutions for regular customers can be arranged - feel free to contact us.

What is the “K” state or the “U” state?

The “K” state is a phenomenon that occurs in nickel-chromium alloys and particularly affects the thermoelectric properties of these alloys. These are the magnetic order states of the individual lattice building blocks.

One normally differentiates between:
  • an “orderly” state (“K” state)
  • a “disorderly” state (“U” state)
Lattice building blocks in the “K” state are in “line and order”, whereas in the “U” state they run chaotically. These states can be generated by certain temperature treatments and undone or reversed as desired. In addition - and this is a common case - there are arbitrary transition states between the two states mentioned above.

What are the effects of ordered states?

The thermal voltage of an NiCr leg in the “K” state may be the equivalent of 2 to 3 °C higher than an identical leg in the “U” state, depending on temperature and test method. In transition states, this value decreases.

Which heat treatments are sheathed thermocouples subjected to?

After the last drawing operation, annealing is used to break down the solidification of the sheath and wires caused by plastic deformation. Sheathed thermocouples are thus soft and easily bendable, so that large changes in the thermoelectric voltage can be reversed. These anneals are consistently at temperatures above 600 °C, i.e. the wires are in the “U” state. In addition, we use a complex second annealing, which ensures that the entire cable is in the stable “K” state and thus a reliable temperature measurement is expected.

How are sheathed thermocouples tested?

Sheathed thermocouples are subjected to a thermoelectric potential test which places the samples in the “K” state.

When can a reliable temperature measurement be expected with sheathed thermocouples?

Only when the sheathed thermocouples are delivered in the stable “K” state can a reliable temperature measurement be expected, which also corresponds to the thermoelectric voltage as determined during the test. We therefore use a complex second annealing, which ensures that the entire cable is in a stable “K” state.

How do thermocouples behave in the different delivered states?

Thermocouples are usually installed so that their measuring point is at an elevated temperature. The temperature along the entire length of the thermocouple then drops, with a given gradient, to room temperature. With a completely homogeneous thermocouple (the thermo legs are absolutely identical from front to back and have no local microstructural changes or impurities), the thermoelectric voltage depends exclusively on the difference between the measuring point and the reference junction. If the thermocouple is no longer homogeneous, deviations from the original thermoelectric voltage occur. These depend on the type and intensity of the inhomogeneity and the temperature profile along the thermocouple. Each type K thermocouple, regardless of the state in which the line was delivered, will change after installation and on first use, as it will always be routed through a temperature range in which the “K” state has been established over a long period of time. It is important that the “K” state also settles at temperatures slightly below 250 °C, only much slower, i.e. it can take weeks.