Siemens M7-400 User Manual

5-52

S7-400, M7-400 Programmable Controllers Module Specifications

A5E00069467-07

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

– and SE– and

 

(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

+ 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

– 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

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