Eaton XN300 - Page 199

26 Analog input module XN-322-10AI-TEKT
26.2 Wiring topic
195 XN300 slice modules 02/24 MN050002EN Eaton.com
26.2.5 How the total tolerance for analog inputs is calculated
In order to illustrate how the analog inputs' tolerance is calculated, we will be
using the same type K thermocouple as an example.
Example showing the formula for total error, error for cold-junction compen-
sation
Refer to  Table 12 Measurement accuracy for total error: ±0.7% of
maximum reading
0.7%: Measurement accuracy relative to the maximum reading of 40 mV for the module's entire ambient
temperature range of 0 to 60 °C
940 °C: Specified measurement range for type K thermocouple
38.9 mV: Thermal voltage of type K thermocouple relative to 940 °C
40 mV: Specified measurement range
This does not include the additional measurement error caused by the
thermocouple's connection resistance or the thermocouple's own
measurement error as a function of the thermocouple class.
When using the internal cold-junction compensation function, a cold-junction
compensation error of ±2 °C is additionally added.
I.e., the total internal module accuracy for a thermocouple measurement
with a type K thermocouple comes up to ±8.8 °C for the module's entire
ambient temperature range of 0 to 60 °C.
Cumulative
error
[940°C]
=
± 0.7 % * 940 °C *
40 mV
= ± 6.8 °C
38.9 mV