II - DCE FEL ČVUT v Praze

Thermocouples
with internal
compensation
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04
Note
The two last channels (channel 6 and 7) of the analog input module SM 331;
AI 8 x TC/4 x RTD are used for temperature compensation by means of
thermal resistor.
Internal sensing of the terminal temperature must be used for compensation
purposes when thermocouples are connected directly or via equalizing
conductors to the module. Each channel group can use one of the supported
types of thermocouple independent of the other channel groups.
Thermocouple
CH0
.
.
.
CH7
Equalizing conductor
(material with same
thermal e.m.f. as
thermocouple)
M+
M-
M+
M-
ADU
SIMATIC S7 Ex Analog Modules
Logic
P5V
M internal
Internal recording
of terminal temperature
Backplane
bus
Fig. 3-8 Connection of thermocouples with internal compensation to an electrically
isolated analog input module
3-31