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Connecting
5.2 Connecting thermocouples
5.2
Connecting thermocouples
Introduction
This section contains additional information on connecting thermocouples.
Compensation of the comparison point temperature
There are various ways of obtaining the comparison point temperature in order to get an
absolute temperature value from the temperature difference between the comparison point
and the measuring point.
Table 5-1
Compensation of the comparison point temperature
Option
No compensation
Using a compensating box
on the supply lines of a
single thermocouple
Internal compensation in
the case of the 2AI TC HF
Extension to a comparison point
The thermocouples can be extended from their connection point by means of compensating
lines to the comparison point (transition to Cu line) or the compensating box. The
comparison point can also be an ET 200S terminal module.
The compensating lines are made of the same material as the wires of the thermocouple.
The supply lines are made of copper. Ensure the correct polarity when connecting.
30
Description
It is not just the temperature of the measuring
point that you need to record: The temperature of
the comparison point (transition from Cu line to
thermocouple line) also affects the thermo-
electromotive force. The measured value on its
own is incorrect.
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 using the 2AI TC ST.
There is a temperature sensor in the TM-E15S24-
AT and TM-E15C24-AT terminal modules. The
temperature sensor reports the temperature of
the terminals to the 2AI TC HF. This value is then
calculated together with the measured value from
the channel of the electronic module.
Comparison point parameters
None
None
2AI TC HF:
•
Reference junction: Yes
2AI TC HF analog electronic module (6ES7134-4NB01-0AB0)
Manual, 04/2007, A5E01076892-01
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