Siemens 6ES7 331-7SF00-0AB0 - Connecting thermocouple through external Pt100 using an external RTD module

Analog input module SM 331; AI 6 x TC Isolated (6ES7331‑7PE10‑0AB0)
16 A5E02398493-02, 11/2008
Connecting thermocouple through external Pt100 using an external RTD module
The flexibility of the structure for DS2 makes it possible to use a separate external Pt100 for each channel. In addition the
channels can be grouped per the user application to share the same external Pt100. This is accomplished by simply
supplying the same temperature value in DS2 for the channels sharing the same reference temperature.
Note
The reference junction can add error to the temperature reading of the AI 6 X TC Isolated module. Careful consideration
should be made in the installation of this junction. To minimize the added error, the reference junction temperature should
remain constant.
Example for transferring a temperature value from a RTD module as a cold-junction temperature for the channel 0…5 to the
AI6xTC:
Input Address of the AI6xTC: 238 (module address)
Input Address of the RTD: 128 (channel address)
Used memory:
M 20.0: request bit for the SFC "WR_REC"
M 20.1: busy bit of the SFC "WR_REC"
MW 22: Return value of the SFC "WR_REC"
MW 0…MW 12: memory for the data transfer (see table below)
AN M 20.0 // checking requirement for new cold-junction temp
AN M 20.1 // checking if the WR_REC is busy or not
JC END // jump over when no transfer is required
A M 20.1 // checking if the WR_REC is busy
JC WRT
// building the memory for the data transfer
L B#16#01 // transferring the temperature in hundredths of
// degrees (Climatic)
T MB 0
L B#16#02 // transferring the temperature in Kelvin
T MB 1
L PIW 128 // reading the Input Address of the used channel from
// the RTD module
T MW 2 // for the channel 0 of the AI6xTC
T MW 4 // for the channel 1 of the AI6xTC
T MW 6 // for the channel 2 of the AI6xTC
T MW 8 // for the channel 3 of the AI6xTC
T MW 10 // for the channel 4 of the AI6xTC
T MW 12 // for the channel 5 of the AI6xTC
// transferring the cold-junction temperature to the AI6xTC
WRT: CALL "WR_REC"
REQ :=M20.0 // Request bit, for a data transfer
IOID :=B#16#54
LADDR :=W#16#EE // Input Address of the AI6xTC
RECNUM :=B#16#2 // Dataset-Number must be set to 2
RECORD :=P#M 0.0 Byte 14 // Pointer to the memory for data
// transfer, with a length of 14 Bytes
RET_VAL :=MW22 // Return Value from the SFC "WR_REC"
BUSY :=M20.1 // Busy Bit from the SFC "WR_REC"
A M 20.1 // checking if the WT_REC is busy
JC END
CLR
= M 20.0 // resetting the requirement for a cold-
// junction temp
END: NOP 0