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Analog Value Processing
When several thermocouples are distributed over areas with different temperature ranges, it is
often advantageous to acquire different reference junction temperatures. In this case, the central
compensating input is no longer used. A separate compensating box is used for each analog input
channel to be compensated. KOMP+and KOMP - remain unconnected.
•
Connect the relevant thermocouple in series with the compensating box.
•
Run the remaining terminal leads from compensating box and thermocouple to the analog
module (terminal M+and M - see Figure 10-5).
•
Set Function Select switch II on the module to "Without reference junction compensation".
Compensation, i.e. correction of the temperature error, subsequently takes place in the com-
pensating box rather than on the module.
The corrected value is thus available at terminals M+and M - of the relevant analog input chan-
nels, and is then converted into a digital value.
Compensating box
Thermocouple
Power
supply
unit
Figure 10-5. Connecting a Compensating Box to the Input of an Analog Input Module
10-8
M+
M -
-
+
–
+ Komp (23)
- Komp (25)
S5-115U Manual
Analog input module
Range
card
6ES5 498-
-1AA11
EWA 4NEB 811 6130-02b
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