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Siemens Simatic S7-400 User Manual

Page 268

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Analog Modules

5-52

S7-400, M7-400 Programmable Controllers Module Specifications

A5E00069467-07

Three-Conductor Connection of a Resistance Thermometer

During three-conductor connection to modules with 4 terminals per resistance
thermometer, you must set up a jumper between M–

and I

C

and SE– and

AGND

(see Figure 5-15).

The module compensates in this circuit for the effect of the line resistance between
the module and the resistance thermometer/resistor.

Make sure that the connected cables I

C

+ and M+ and the cables SO and SE+ are

directly connected to the resistance thermometer.

To get an accurate measurement, make sure that the connected cables M+, I

C

+

and I

C

and the cables SE+, SO and AGND are the same length and have the

same cross-section.

I

C

M

+

M

I

C+

I

C–

SE+
SE–
SO
AGND

Figure 5-15

Three-Wire Connection of Resistance Thermometers to an AI

Two-Conductor Connection of a Resistance Thermometer

With a two-conductor connection, you must insert jumpers on the module between
M

+

and I

C+

and between M

and I

C–

.

Note: Cable resistance is also measured.

M

+

M

I

C+

I

C–

Figure 5-16

Two-Wire Connection of Resistance Thermometers to an AI

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