Siemens SIMATIC S7-1500 Manual page 30

Parameters/address space
4.3 Declaration of parameters
Reference junction for TC
The following settings can be configured for the reference junction parameter:
Table 4- 3 Possible parameter assignments for the reference junction parameter TC
Setting
Fixed reference temperature
Dynamic reference temperature
Internal reference junction
Reference channel of the module
Hardware interrupt 1 or 2
Enabling of a hardware interrupt at violation of high limit 1 or 2 or low limit 1 or 2.
Low limit 1 or 2
Specifies the low limit threshold that triggers hardware interrupt 1 or 2.
High limit 1 or 2
Specifies the high limit threshold that triggers hardware interrupt 1 or 2.
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Description
The reference junction temperature is configured and stored in the module as
a fixed value.
The reference junction temperature is transferred in the user program from the
CPU to the module by data records 192 to 199 using the WRREC (SFB 53)
instruction.
The reference junction temperature is determined using an integrated sensor
of the module.
The reference junction temperature is determined using an external resistance
thermometer (RTD) at the reference channel (COMP) of the module.
Analog input module AI 8xU/I/RTD/TC ST (6ES7531-7KF00-0AB0)
Manual, 09/2016, A5E03484864-AD