Siemens ET 200S - Page 402

Analog Electronic Modules
12-46
Distributed I/O System ET 200S
EWA 4NEB 780 6024-02 07
12.2.2 Connecting Thermocouples
Introduction
This section contains additional information on connecting thermocouples.
Compensation of the Reference Junction Temperature
There are various ways of obtaining the reference junction temperature in order to
get an absolute temperature value from the temperature difference between the
reference junction and the measuring point.
Table 12-65Compensation of the Reference Junction Temperature
Option
Description Reference Junction
Parameters
No compensation You record not only the temperature
of the measurement point. The
temperature of the reference junction
(transition from Cu line to
thermocouple line) also affects the
thermo-electromotive force. The
measured value is thus errored.
None
Use of a
compensating box
on the incoming
lines of a single
thermocouple
You compensate using a
compensating box. The
compensating box is the transition
point from the Cu line to the
thermocouple line. No further
processing is necessary through the
2AI TC Standard.
None