WIKA TC12-M - Handbuch (Seite 10)

GB
3. Specifications
14083458.01 09/2013 GB/D
WIKA operating instructions models TR12, TC12 (Ex i) 10
3.2 Thermocouples
3.2.1 Sensor types
Type Recommended max. operating temperature
K 1,200 °C
J 800 °C
E 800 °C
N 1,200 °C
Tolerance values of the thermocouples per IEC 60584-2 / ASTM 14.03 E230
(Reference temperature 0 °C)
Type Thermo-
couple
Tolerance value Class Temperature
range
Tolerance value
K
N
NiCr-Ni
(NiCr-NiAl)
NiCrSi-NiSi
IEC 60584 part 2
1 -40 ... +1,000 °C ±1.5 °C or 0.0040 ∙ | t |
1) 2)
2 -40 ... +1,200 °C ±2.5 °C or 0.0075 ∙ | t |
ASTM 14.03 E230 Special
0 ... +1,260 °C ±1.1 °C or ±0.4 %
Standard 0 ... +1,260 °C ±2.2 °C or ±0.75 %
J Fe-CuNi
IEC 60584 part 2
1 -40 ... +750 °C ±1.5 °C or 0.0040 ∙ | t |
2 -40 ... +750 °C ±2.5 °C or 0.0075 ∙ | t |
ASTM 14.03 E230 Special
0 ... +760 °C ±1.1 °C or ±0.4 %
Standard 0 ... +760 °C ±2.2 °C or ±0.75 %
E NiCr-CuNi
IEC 60584 part 2
1 -40 ... +800 °C ±1.5 °C or 0.0040 ∙ | t |
2 -40 ... +900 °C ±2.5 °C or 0.0075 ∙ | t |
ASTM 14.03 E230 Special
0 ... +870 °C ±1.0 °C or ±0.4 %
Standard 0 ... +870 °C ±1.7 °C or ±0.5 %
1) ItI is the value of the temperature in °C without consideration of the sign
2) The greater value applies
There are different notations for thermocouple type K in Europe and North America:
Europe: NiCr-Ni or NiCr-NiAl
North America: Ni-Cr / Ni-Al
There is no material difference, the two designations are based on historical reasons.
3.2.2 Potential measurement uncertainties
Important factors which counteract the long-term stability of thermocouples.
Ageing effects/poisioning
■ Oxidation processes in thermocouples which are not appropriately protected (“bare”
thermocouple wires) result in falsifications of the characteristic curves.
■ Foreign atoms (poisoning) that diffuse into the original alloys lead to changes of these
original alloys and thus falsify the characteristic curve.
■ The influence of hydrogen leads to the embrittlement of the thermocouples.
The Ni leg of the type K thermocouple is often damaged by sulphur which is contained in
exhaust gases, for example. Thermocouple types J and T age slightly, as the pure metal leg
oxidises first.
In general, rising temperatures cause accelerated ageing effects.