Siemens SIMATIC ET 200S Manual page 476

Analog Electronic Modules
Compensation of thermocouples with a compensating box
As well as the error limits of the 2AI TC Standard electronic module (see Table
"Technical specifications" in this chapter) you must also take the accuracy of the
compensating box into account.
Compensation of thermocouples with a Pt100 on the 2AI RTD Standard
Wiring rules
Additional technical
specifications on the error
limits of the 2AI TC li it f th 2AI TC
* In the case of thermocouples with a characteristic curve with a very shallow gradient, these
errors can lead to a major measurement discrepancy.
For the following thermocouples, this leads to a restriction of the input range of the
thermocouples in which the accuracy specifications of the manual apply:
Type N: –100 °C
Type K: –230 °C
Type E: –230 °C
13-92
Factors affecting the accuracy of the temperature measurement
Ensure there is good thermal contact between the
reference junction and the Pt100 used for compensation.
We recommend that you wire the Pt100 with a
four-conductor connection.
The accuracy of the thermal resistor (Pt100) used for
compensation must be taken into account.*
The error of the measurement input (2AI RTD Standard)
used for compensation must be taken into account.*
ET 200S Distributed I/O System
EWA-4NEB780602402-09