Siemens S7-1500 Manual page 14

Wiring
3.1 Wiring and block diagram
Resistor circuitry of the encoders
To detect a wire break, it is necessary that enough quiescent current is flowing even when
the encoder contacts are open. Connect a resistor to the encoder contacts for this reason,
see figure below.
Rated input voltage:
24 VUC
48 VUC
125 VUC
Figure 3-2
14
Resistance:
16 kΩ ... 21 kΩ with 1.0 W
37 kΩ ... 53 kΩ with 0.5 W
101 kΩ ... 156 kΩ with 0.25 W
Resistor circuitry of the encoders
Digital input module DI 16x24...125VUC HF (6ES7521-7EH00-0AB0)
Manual, 12/2016, A5E35681478-AC