SIMATIC S7-400 Digital Input Module 6ES7421-7DH00-0AB0

The SIMATIC 6ES7421-7DH00-0AB0 is a 16-channel digital input module for the S7-400 PLC system. It features high isolation and diagnostic alarms for reliable industrial signal acquisition.

Technical Specifications

Manufacturer: Siemens
Order Number: 6ES7421-7DH00-0AB0
Product Family: SIMATIC S7-400
Module Type: Digital Input (DI) SM 421
Number of Channels: 16
Input Voltage (UC): 24 - 60 V DC / 15 - 60 V AC (47-63 Hz)
Signal "1" Range: 15 to 72 V DC / -15 to -72 V DC / 15 to 60 V AC
Signal "0" Range: -6 to +6 V DC / 0 to 5 V AC
Input Current (Signal "1"): 4 to 10 mA (typical 4 mA)
Input Delay: Configurable (0.5 ms, 3 ms, 10 ms, 20 ms)
Wire-Break Detection: Yes (current > 0.7 mA)
Isolation: 1500 V AC (Channels to bus and between groups)
Cable Length: Max. 1000 m (shielded), 600 m (unshielded)
Backplane Bus Current: 150 mA max. (5V DC)
Power Loss: Typical 8 W
Dimensions (WxHxD): 25 x 290 x 210 mm
Weight: Approx. 600 g

Installation & Compatibility

This module installs into a SIMATIC S7-400 rack. It is compatible with 2-wire and 3-wire sensors. Use parameterization software (like STEP 7) to configure input delays and diagnostic alarms. Ideal for monitoring switches, sensors, and buttons in harsh industrial environments.

Shipping & Warranty

Shipped via FedEx, UPS, or DHL. Package includes the digital input module. This product is covered by a 12-month warranty.

Frequently Asked Questions

What does "potential separation" mean?
It means the input channels are electrically isolated from each other and the backplane bus, protecting the PLC from external voltage spikes.

How does wire-break detection work?
The module monitors a small current (over 0.7 mA). If the current falls below this (open circuit), it can trigger a diagnostic alarm.

Can I connect AC and DC sensors simultaneously?
Yes, the module accepts both AC and DC voltage signals on any channel within the specified range.

What is the purpose of adjustable input delay? It filters out electrical noise or contact bounce by ignoring signal changes shorter than the set delay time (e.g., 0.5 ms to 20 ms).

Is an external power supply needed for the sensors?
Yes, you must provide a separate 24-60V power source for the connected field devices and sensors.