Distributed I/O System ET 200S

4.3.2 Connecting Thermocouples
Introduction
Analog electronics modules
4.3 Basics of analog value processing
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 4-25 Compensation 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 thermoelectromotive
force. The measured value is thus
errored.
None
Use of a compensating You compensate using a compensating box. The None
box on the incoming lines compensating box is the transition point from the
of a single thermocouple Cu line to the thermocouple line. No further
processing is necessary through the 2AI TC
Standard.
Use of a Pt 100 Climatic You can record the reference junction
The parameter assignment of the IM151-1
Range resistance temperature using a resistance thermometer and the 2AI TC must be coordinated:
thermometer to record the
reference junction
(Pt 100 Climatic Range). Given appropriate
parameter assignment, this temperature value in
• 2AI RTD Standard assigned
parameters to the Pt 100 climatic
temperature (best method) the ET 200S is distributed to the 2AI TC Standard range at the correct slot;
modules and calculated in the modules together
with the temperature value obtained for the
measurement point.
• 2AI TC Standard: Reference junction :
RTD; select reference junction number
1
Number of reference junctions: 1
• IM : Assignment of the reference
junction to a slot with the 2AI RTD
Standard; selection of a channel;
Internal compensation in There is a temperature sensor in the TM-E15S24- • 2AI TC High Feature:
the case of the 2AI TC AT and TM-E15C24-AT terminal modules. The Reference junction: Yes
High Feature
temperature sensor reports the temperature of
the terminals to the 2AI TC High Feature. This
value is then calculated together with the
measured value from the channel of the
electronic module.
ET 200S
Manual, 12/2005, A5E00514527-03 4-19