9. Compensation and Extension Cables:
In accordance with DIN 43 722,
compensation cables are marked with the letter "C", which is placed after the
code letter of the corresponding thermocouple (e.g. "KC"). The electrical
conductors (i.e. the flexible strands or solid wires) consist of so-called
substitute materials that have a different chemical composition from the
materials of the corresponding thermocouple (see the table at the end of this
section). Various substitute materials may be used for a thermocouple type, with
an additional letter "A" or "B" (e.g. "KCA" and KCB") being added to the
designation of the cable in this case. The substitute materials have the same
thermoelectric properties as the corresponding thermocouple in the application
temperature range permissible for compensation cables. For the temperature range
permissible according to cable type, see DIN 43 722. Compensation
cables are used for thermocouple types K, N, R, S and B, as the substitute
materials (particularly in the case of noble metal thermocouple types R, S and
B) are much better priced than the (original) materials of the corresponding
material. Extension cables for thermocouples (T/C extension cables) are
designated, in accordance with DIN 43 722, with the letter "X", which is placed
after the code letter of the corresponding thermocouple (e.g. "KX"). The
electrical conductors consist of materials that nominally have the same chemical
composition as the (original) materials of the corresponding thermocouple. The
thermoelectric voltage of the conductor pairs, however, only needs to match the
standardized basic values of the corresponding thermocouple to a temperature of
200°C (only up to 100°C for type TX). T/C extension cables are available for
thermocouple types K, N, J, T and E (all types in accordance with DIN IEC 584)
as well as for types L and U (in accordance with DIN 43710). The limit
deviations (tolerances) of the compensation and T/C extension cables are defined
in DIN 43 722 (or in DIN 43 710 for cable types LX and UX) and apply to the
cable’s condition at the time it is supplied. The limit deviation is the maximum
additional deviation in microvolts that is produced in a measuring circuit if a
compensation or T/C extension cable is inserted into it and the cable is
inserted within its permissible temperature range. The loop
resistance of compensation and T/C extension cables is of secondary importance
in many cases, as modern electronic measuring devices have high input
resistance, which means that even cable resistance of several kiloohms fails to
cause significant measurement error.
The following table provides an overview of the
materials and colour codes of compensation and T/C extension cables and the
materials of the corresponding thermocouples
Tabelle 1:
Werkstoffe und Kennfarben (Übersicht) / Materials and
colour codes |
Thermopaare thermocouples
|
Ausgleichs- und Thermoleitungen compensation and extension cables
|
Kennfarben der Isolierung 2) colour codes
2)
|
Norm standard
|
Typ type
|
Werkstoffe / materials
+ Pol - Pol |
Typ
1) type 1)
|
Werkstoffe / materials
+ Pol - Pol |
+ Pol |
- Pol |
Mantel 3) sheath 3) |
Norm standard
|
DIN
EN 60584 |
J |
Fe |
CuNi |
JX |
Fe |
CuNi |
schwarz black
|
weiß white
|
schwarz black
|
DIN
EN 43722 |
T |
Cu |
CuNi |
TX |
Cu |
CuNi |
braun brown
|
weiß white
|
braun brown
|
E |
NiCr |
CuNi |
EX |
NiCr |
CuNi |
violett violet
|
weiß white
|
violett violet
|
K |
NiCr |
Ni |
KX |
NiCr |
Ni |
grün green
|
weiß white
|
grün green
|
KCA |
Fe |
CuNi |
KCB |
Cu |
CuNi |
N |
NiCrSi |
NiSi |
NX |
NiCrSi |
NiSi |
rosa pink
|
weiß white
|
rosa pink
|
NC |
Cu |
CuNi |
R |
Pt 13% Rh |
Pt |
RCA |
Cu |
CuNi |
orange orange
|
weiß white
|
orange orange
|
RCB |
Cu |
CuNi |
S |
Pt 10% Rh |
Pt |
SCA |
Cu |
CuNi |
orange orange
|
weiß white
|
orange orange
|
SCB |
Cu |
CuNi |
B |
Pt 30% Rh |
Pt 6% Rh |
BC |
Cu |
Cu |
grau grey
|
weiß white
|
grau grey
|
DIN
EN 43710 |
U |
Cu |
CuNi |
UX |
Cu |
CuNi |
rot red
|
braun brown
|
braun brown
|
DIN
EN 43714 |
L |
Fe |
CuNi |
LX |
Fe |
CuNi |
rot red
|
blau blue
|
blau
blue |
1) " ...C, ...CA, ...CB " :
Ausgleichsleitungen / compensation
cables " ... X : Thermoleitungen
/ extension cables for thermocouples 2) siehe
Seite "Farbtabelle für internationale Kennfarben der Temperatur -
Meßtechnik" see "international colour codes
applied to temperature measuring engineering" 3) Außengeflechte
(z.B aus Glasseide oder Stahldraht) besitzen einen entsprechend gefärbten
Kennfaden im Geflecht.
Uncoloured sheaths (e.g. armourings or fiber glass) have an appropriately coloures tracer.
|
Go to the Practice page (Installing Temperature Sensors)
|