Digital Modules
4-19
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Technical Specifications of the SM 421; DI 32 x 24 VDC
Programming package
Associated programming
package
As of STEP 7 V 2.0
Dimensions and Weight
Dimensions W H D
(in millimeters)
25 290 210
Weight Approx. 600 g
Data for Specific Module
Number of inputs 32
Length of cable
• Unshielded
• Shielded
Max. 600 m
Max. 1000 m
Voltages, Currents, Potentials
Power rated voltage of the
electronics L+
24 VDC
• Reverse polarity protection Yes
• Power failure buffering None
Number of inputs that can be
triggered simultaneously
32
Isolation
• Between channels and
backplane bus
Yes
• Between channels and
power supply of the
electronics
No
• Between the channels No
Permitted potential difference
• Between the different
circuits
75 VDC / 60 VAC
Insulation tested with
• Channels against
backplane bus and load
voltage L+
500 VDC
Current consumption
• From the backplane bus Max. 30 mA
• From supply voltage L+ Max. 30 mA
Power dissipation of the
module
Typ. 6 W
Status, Interrupts, Diagnostics
Status display Green LED per
channel
Interrupts None
Diagnostic functions None
Substitute value can be applied No
Sensor Selection Data
Input voltage
• Rated value
• For signal “1”
• For signal “0”
24 VDC
11 V to 30 V
–3 V to 5 V
–30 V to 5 V as of
version 03
Input current
• At signal “1” 6 mA to 8 mA
Input delay
• At “0” to “1”
• At “1” to “0”
1.2 ms to 4.8 ms
1.2 ms to 4.8 ms
Input characteristic curve To IEC 61131; type 2
Connection of two-wire BEROs Possible
• Permitted bias current Max. 2.5 mA
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