About SIMATIC S7-400, digital input SM 421, isolated 16 DI

SIMATIC S7-400 Digital Input SM 421The SIMATIC S7-400 Digital Input SM 421 is an isolated 16-channel digital input module for the S7-400 series.Key Features: - 16 isolated digital input channels- Universal compatibility: 120-230 V DC- Alarm and diagnostics: for efficient error detection and troubleshooting- Galvanic isolation: for reliable operationKey Specifications: - Input type: Digital- Number of channels: 16- Input voltage: 120-230 V DC- Isolation: Galvanic- Compatibility: S7-400 series 

Siemens SIMATIC S7-400 SM 421 Digital Input Module

Product Type: SM 421 Digital Input Module
Number of Inputs: 16 DI (isolated)
Input Type: AC/DC, Type 2 (IEC 1131-2)
Rated Voltage (UC): 120/230 V AC/DC (4763 Hz)

Power & Current

• Backplane Bus Current (5 V DC): Max. 80 mA

• Power Loss (typical): 12 W

Digital Inputs

• Number of Inputs: 16

• Controllable Inputs: Max. 16 simultaneously

• Signal Levels:

  • 0: 040 V AC / -40 to +40 V DC

  • 1: 74264 V AC / 80264 V DC

• Input Current (typical):

  • At 120 V: 10 mA AC / 1.8 mA DC

  • At 230 V: 14 mA AC / 2 mA DC

• Permissible Quiescent Current (Signal 0): 6 mA AC / 2 mA DC

Input Timing

• 0 1 Transition: Max. 20 ms (AC), 15 ms (DC)

• 1 0 Transition: Max. 30 ms (AC), 25 ms (DC)

Cabling

• Max Cable Length (Shielded): 1,000 m

• Max Cable Length (Unshielded): 600 m

Encoder Support

• Connectable Sensors: 2-wire sensor

• Permissible Quiescent Current: Max. 5 mA AC

Diagnostics & Status

• Diagnostics Function: No

• LED Indicator: Yes, green for input status

Isolation & Safety

• Channel-to-Channel Separation: Yes (grouped in 4s)

• Channel-to-Backplane Bus Separation: Yes

• Tested Isolation Voltage: 1,500 V AC

Dimensions & Weight

• Width: 25 mm

• Height: 290 mm

• Depth: 210 mm

• Weight: ~650 g 

Technical Details