Digital Modules
4-34 S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Terminal Assignment Diagram for Redundant Supply of Sensors

The figure below shows how sensors can additionally be supplied by means of Vs

with a redundant voltage source – for example, via another module).

Vs

M

L+ 1 L+

2 L+

to the sensors

±

Digital input

module

Short-circuit-

proof driver

Figure 4-7 Terminal Assignment Diagram for the Redundant Supply of Sensors of the

SM 421; DI 16 24 VDC

Technical Specifications of the SM 421; DI 16 24 VDC
Dimensions and Weight
Dimensions W H D
(in millimeters) 25 290 210
Weight Approx. 600 g
Data for Specific Module
Number of inputs 16
Length of cable
•Unshielded
input delay
– 0.1 ms
– 0.5 ms
– 3 ms
Max. 20 m
Max. 50 m
Max. 600 m
•Shielded
input delay
– 0.1 ms
– 0.5 ms
– 3 ms
Max. 30 m
Max. 70 m
Max. 1000 m
Voltages, Currents, Potentials
Rated supply voltage of the
electronics and sensor L+ 24 VDC
•Reverse polarity protection Yes
Number of inputs that can be
triggered simultaneously 16
Isolation
•Between channels and
backplane bus Yes
•Between channels and
power supply of the
electronics
No
•Between the channels Yes
– In groups of 2
Permitted potential difference
•Between the different
circuits 75 VDC, 60 VAC
Insulation tested with
•Channels against
backplane bus and load
voltage L+
500 VDC
•Channel groups between
themselves 500 VDC
Current consumption
•From the backplane bus
•From the power supply L+
Max. 130 mA
Max. 120 mA
Power dissipation of the
module Typ. 5 W