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II - DCE FEL ČVUT v Praze

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Internal<br />

compensation<br />

Thermocouple<br />

connection<br />

options<br />

Abbreviations<br />

I/O Modules with Intrinsically-Safe Signals<br />

C79000-G7076-C152-04<br />

The following conditions must be observed:<br />

SIMATIC S7 Ex Analog Modules<br />

External compensation by means of a compensation box can only be<br />

carried out for one specific type of thermocouple. This means all channels<br />

of this module which operate with external compensation must be<br />

parameterized for the same type of thermocouple.<br />

Module diagnostic signals ”incorrect parameters in module” and<br />

”reference channel error” for the corresponding channels (0..5) in the case<br />

of incorrect parameterization.<br />

The parameters of a channel group apply to both channels of this channel<br />

group (e.g. type of thermocouple, integration time, etc.)<br />

For the purposes of internal compensation, you can form the reference<br />

junction at the terminals of the analog input module. In this case, you must<br />

route the compensating conductors to the analog module. The internal<br />

temperature sensor senses the terminal temperature of the module. The<br />

thermocouples (also different types) connected to the module are<br />

compensated with this temperature.<br />

Note<br />

For the analog input module SM 331; AI 8 x TC/4 x RTD, the compensation<br />

box is connected to terminals 18 and 19.<br />

The thermal resistor is connected to terminals 16, 17, 18 and 19 in order to<br />

register the reference junction temperature.<br />

Figs. 3-4 to 3-8 show the different connection options for thermocouples with<br />

external and internal compensation.<br />

The information provided in Section 3.2 on differences in potential UCM and<br />

UISO between the individual circuits still retains its validity.<br />

The abbreviations used in the Figs. 3-4 to 3-10 have the following<br />

significance:<br />

IC+ : Positive connection of constant current output<br />

IC- : Negative connection of constant current output<br />

M+ : Measuring conductor (positive)<br />

M- : Measuring conductor (negative)<br />

L+ : Power supply connection 24 V DC<br />

M : Ground terminal for 24 V DC power supply<br />

P5V : Supply voltage of module logic<br />

Minternal: Ground of module logic<br />

UV : Isolated supply voltage for compensation box<br />

3-27

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