Siemens SIMATIC S5-115U, User Manual

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S5-115U Manual Analog Value Processing
Connecting Thermocouples with Compensating Box
The influence of the temperature on the reference junction (in the terminal box, for instance)
must be equalized using a compensating box. Please observe the following:
•
The compensating box must have an isolated power supply.
• The power supply unit must have a grounded shielding winding.
Compensate as follows when all thermocouples connected to the module's inputs have the same
reference junction:
•
Provide a separate compensating box for each analog input module
• Bring the compensating box into thermal contact with the terminals
• Apply compensating voltage to pins 23 and 25 (KOMP+and KOMP -) on the analog input mo-
dule (Figure 10-4)
• Set Function Select switch II on the module for operating a compensating box (see also
Table 10-2)
Figure 10-4. Connecting Thermocouples
Thermocouple
Terminal box
Compensation unit
A resistor on the jumper,
which is balanced at 0 °C, is
temperature-dependent,
and produces a compen-
sating voltage when the
temperature rises or drops
+
-
M -
M+
Analog input module
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23
25
Power
supply
unit
Reference bus
=
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Range
card
6ES5 498-
-1AA11
Detailed information on thermocouples and compensating boxes can be found in Catalog MP 19.
EWA 4NEB 811 6130-02b
10-7