II - DCE FEL ČVUT v Praze

Internal
compensation
Thermocouple
connection
options
Abbreviations
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04
The following conditions must be observed:
SIMATIC S7 Ex Analog Modules
External compensation by means of a compensation box can only be
carried out for one specific type of thermocouple. This means all channels
of this module which operate with external compensation must be
parameterized for the same type of thermocouple.
Module diagnostic signals ”incorrect parameters in module” and
”reference channel error” for the corresponding channels (0..5) in the case
of incorrect parameterization.
The parameters of a channel group apply to both channels of this channel
group (e.g. type of thermocouple, integration time, etc.)
For the purposes of internal compensation, you can form the reference
junction at the terminals of the analog input module. In this case, you must
route the compensating conductors to the analog module. The internal
temperature sensor senses the terminal temperature of the module. The
thermocouples (also different types) connected to the module are
compensated with this temperature.
Note
For the analog input module SM 331; AI 8 x TC/4 x RTD, the compensation
box is connected to terminals 18 and 19.
The thermal resistor is connected to terminals 16, 17, 18 and 19 in order to
register the reference junction temperature.
Figs. 3-4 to 3-8 show the different connection options for thermocouples with
external and internal compensation.
The information provided in Section 3.2 on differences in potential UCM and
UISO between the individual circuits still retains its validity.
The abbreviations used in the Figs. 3-4 to 3-10 have the following
significance:
IC+ : Positive connection of constant current output
IC- : Negative connection of constant current output
M+ : Measuring conductor (positive)
M- : Measuring conductor (negative)
L+ : Power supply connection 24 V DC
M : Ground terminal for 24 V DC power supply
P5V : Supply voltage of module logic
Minternal: Ground of module logic
UV : Isolated supply voltage for compensation box
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