Siemens SIMATIC ET 200AL, System Manual

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Thermocouples
5.3 Compensation for the reference junction temperature
Analog value processing
Function Manual, 06/2014, A5E03461439-AC
101
Connection example
Connection with M12 compensation connector
Connect the thermocouple to the M12 compensation connector directly or with compensating
lines. Install the M12 compensation connector to the X1 circular socket (channel 0) of the
CM IO 4 x M12 at the 4 AI TC High Feature.
Connection without M12 compensation connector
To measure the referent junction temperature, connect an external Pt1000 (with α = 003851)
to terminals 1 and 3 using copper cables. The thermal resistor Pt1000 must be positioned in
the area of the reference junction. Connect the thermocouples to terminals 2 and 4 from the
reference junction with copper cables.
Connecting additional thermocouples
You can connect additional thermocouples to the circular sockets X2 to X4 on the
CM IO 4 x M12 of the 4 AI TC High Feature. The temperature of reference junction collected
by measuring the resistance value at the X1 circular socket applies to all channels of the
module that you have selected for this type of compensation.
The figure below shows a connection example "RTD (0)" as reference junction with M12
compensation connector and integrated thermal resistor Pt1000:
①
Direct connection of the thermocouple or with compensating lines
②
Thermocouple
③
M12 compensation connector (terminals 1 and 3 with internal Pt1000) only at X1 circular
socket. The comparison value of the M12 compensation connector at circular socket X1 also
applies to thermocouples at X2, X3 and X4.
Figure 5-18 Connection example "RTD (0)" as reference junction in the M12 compensation connector