Rockwell Automation 1790P-T4T0 CompactBlock LDX I/O Thermocouple Modules - Manual (Page 43)

Publication 1790-UM003A-EN-P
Module Data, Status, and Channel Configuration for DeviceNet 3-13
Thermocouple Error
The table below summarizes thermocouple error (for more Thermocouple
Type information see Appendix C).
Thermocouple Lead Wire Error
An error is introduced by the resistance of the thermocouple lead wire.
The lead wire resistance in combination with the module input
impedance acts as a voltage divider of the source thermoelectric voltage.
Use the following table to estimate this error.
CJC Error
If the internal CJC compensation is turned off, an error factor is
introduced for either the external CJC or the estimated cold junction
value.
Table 3.10 Thermocouple Error
Thermocouple
Type Useable Range °C Standard Tolerance
Error
*
* Whichever error factor is greater.
Special Tolerance
Error
*
B 870 to 1700 ±0.5% ±0.25%
E 0 to 900
-200 to 0 ±1.7°C or ±0.5%
±1.7°C or ±1% ±1°C or ±0.4%
±1°C or ±0.5%
J 0 to 750 ±2.2°C or ±0.75% ±1.1°C or ±0.4%
K 0 to 1250
-200 to 0 ±2.2°C or ±0.75%
±2.2°C or ±2% ±1.1°C or ±0.4%
NA
R 0 to 1450 ±1.5°C or ±0.25% ±0.6°C or ±0.1%
S 0 to 1450 ±1.5°C or ±0.25% ±0.6°C or ±0.1%
T 0 to 350
-200 to 0 ±1°C or ±0.75%
±1°C or ±1.5% ±0.5°C or ±0.4%
NA
N 0 to 1250 ±2.2°C or ±0.75% ±1.1°C or ±0.4%
Table 3.11 Thermocouple Lead Wire Error
Thermocouple Wire Resistance
(ohms per double foot -
resistance out and back per foot) Error Impact
0.1 ohm insignificant
1 ohm insignificant
10 ohm 0.0004%
100 ohm 0.004%
1000 ohm 0.04%
10,000 ohm 0.4%